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Abstract

Oxytocin (OT) has been implicated in the formation and maintenance of various social relationships, including human romantic relationships. Competing models predict, alternatively, positive or negative associations between naturally-occurring OT levels and romantic relationship quality. Empirical tests of these models have been equivocal. We propose a novel hypothesis ('Identify and Invest') that frames OT as an allocator of psychological investment toward valued, vulnerable relationships, and test this proposal in two studies. In one sample of 75 couples, and a second sample of 148 romantically involved individuals, we assess facets of relationships predicting changes in OT across a thought-writing task regarding one's partner. In both studies, participants' OT change across the task corresponded positively with multiple dimensions of high relationship involvement. However, increases in participants' OT also corresponded to their partners reporting lower relationship involvement. OT increases, then, reflected discrepancies between assessments of self and partner relationship involvement. These findings are robust in a combined analysis of both studies, and do not significantly differ between samples. Collectively, our findings support the 'Identify and Invest' hypothesis in romantic couples, and we argue for its relevance across other types of social bonds.
Oxytocin and Vulnerable Romantic Relationships

 ! "#$%&'()

*" %+!!,!%&-././.,(
*" %+!!&,!%(!
 &!
#*" %"!,!%&-././.,(
*" %.!"!*.0,!*. 1,(
("*" %+!!(12#2
,!%&-././.34 56. .
7.5'."
248.!24
).55349:.%;."
"<5434
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

Abstract
'-!:'< "%  %
."..  "1 "
"!"&.!=
.' "/.! "%
/.)""!":>?%!?@<
% '%"! &.
."""&.? "%4A
." "%3 !.&
%%""'.=&0
@"?.""@'0
""!& ." %" 
B&""@'""
"" 'C
& %%"" 
;. !%.
;!& "1!.;."">?%!
?@!" ."&.%
!"%
!&5-!9 "9"9.!
!
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
#
Introduction
'-!:'<."" "%
".  "!&0 "D
 "%'"!"..
:&E&F1 2< 0&..
:1&!F GG<)"!!'@.
%"  "
-:+F+G4G902229
1GG9822A< .
 "D "%'&".
"=:2912<(%.
-"  %'"=% 
"5% "% %"
"%:) GG<90=.%  .&
":( 22<9. . .&
 .".C:*D22G<-" 
;&""&'"%.%
"=%  :F*.2%
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

""""<? ."%.'"! =
"" !="."=:
1"2A9. FH.2I<
 ."0"%'E.
-"/.'@%.JK %
L:29"I4<J.%
. %'.
 -" " &"
:E2<) .".
% !"!&
..!".' ".%%.
/..%.!=.'
7.& %'@. 
 "; K1 1L""
&"/.!M '.
 @% ":-!
%<./.=%& ..:
  !"!<:1GG39,=22A<
(;&""8- "( 
:2<%.>&@-"'&"
".! +%"=% 
.".;.%'!"!&
.%>/.!@:$&F 
22A9&22A9B=$.2239B=$.2<
1.'&. !""@
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
A
5.!:( 2<%."!
&.@'M"@" "!
 KE%L"&
"/.!'? "" "
: %M-!<'.%.
>""@ 0.%"
:!22I9!22< ""-"%.
%;.""  "% 
.":( 2#<
)""&!C"
(..""1 1 0
."&%" :$
22A9B=$.2<7.""E%
0.%" .""!
":!22<&%;!
C
&!;&"" %
".%" &
"'?.'
%."!.&."
B'0 .%.&
 .! %.@"!M
"!.%:8F7
GGA<8.""%&
/.& :2<'-! ="
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
I
%.& ."!"%":1"2A<
%.  ""%%
.!
.".- ""&."
"'&""H..& 
"& !/." %
.':( 2<!
:22<"' & &"0% 
% "&!=D%' =%
"."&% &0%!
..5 '""!:&
"!<.&":)=.22G9
8 2<
'."" E% ""
.%" '&
E%".D' .%
K""L:!22I9"4#<%!:22<
-"!N.'K"O"P
&L:"I<'."".""5'
."="
?&!:22<.'
%.%& . %& !"""
%.?% .E% ""
& ". :!222<
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
4
"&.&.?(.!&0
" !.""%
" ?(.!&. !
.&."&"%""
% ?.&"-
"&.@'" .
&.@&" .@'
"!"@" 
"""-% "
&%"" M J";!&
"@ @&J.!
'
%' ". !C.! !
%&".!'"
"%.)0 !.0.
.""!&!% ""
."="'%.%0'. "
''9&.!&
-  '& "&0"
Study 1
Method

).4A-..": Q4(*QA#4<% 
"!!..N"""..!
"&"! 0"%
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
3
""@ """-.
 "&" 9 
""& :(*Q# <) 
':>@ . <G.
'.#.?
 "& .%...
 "%.:%!" 0<""
"R%% 
""".% " %.!
 '';!%.%
".:IG<Q=3ASA:AI<Q4IQ23"!
1%".."&
 "D&!22." "&
%&32R"& "%22.)
"" &!. %. 
"   "  !!% 1 "
 "D!T32R"&%A*&
 " !&"% 

1."!. ".!
"." %"% ""&
 ..!;%&%/. 
" "% "%;/.
 """& ."% .=&0
8&0"" "/.8%
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
G
./.:A .%%
.=&0< "&+"%
!% "%/..&0
" ";.%%&=.".!
.B=:22A<.
%'.%&"" !0
." . % . %':
&*"F$22< .%&'!% 
D$%(:*?=G2=A#<&&."G2R!%'
% "0

?;%/.""" "
% .-"&
!8;%
( :2<%.&.""""
 !&'%% 
"
.=&0'.&
"%.!:(02%.! !- 
'!& .%K" L<+"&
"%""&%&.5
K+"%& .0.!."&!.
"&.&!!.""!.&!
&!."&!.&!.!.
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
2
"&."!.&!&!.".!"
&!.
?!.@.%0(!.%&
.!..%&L
.=&0&" ""0.
"&"J" "&&
."". &
""""=" .%% 
!)..!%."%'
".."/.:&<
%&0 "..:<
% %""@"&%
 5-&""% 
"9-&""&"
M9-&"""
7&. !%
&"% "'!
2%3:R<" &.
 !7% &";& 
!5I#44"!7&%!
:UQ4442%& <
+" "!% ."
&"/.%.=&0
..5:<+=(";? ?!:+(??9
GG3<9:<+7"V.!1 "?!:+7V1?9
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

8( "F 222<9:<!F8!@:22I< 
E(/."% "!&0
80:2<9:<I=  .%(7""% 
1F10:22<9:<2=  .%%.&"
:"% .". "!B8.<)
"& .%.!5:%<=  .%
*1&":K?& !&!
?@%%L<9=  .%*1$0&
":K?& . . 0& !"0?@
0&%L<)0"""%="=
"7"=(";? ?!) 
.%7" :( "GGI< 
-! "";!
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!QG4W2229& % " .
"
1 " .% "> @> @
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7(??5-"M..M" M%..=
% -.!""-.D%9A
.%+7V1?%  ."9
"99%.99
0".%.%A3R%
1 )..5"!!": 
!-=";<9 !: 
. ."".<"&"@% !: .
.%!&"@% !< ..
/."0""/.!&.%!
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
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:"" ".Q4#IA4244<( !
"!:..'@1@O222P(+(("<
 "&. -" 
)-:""-%<: <
%&!""%% 
" -;%"$MEC
:SA<%  -"M..%..=
% %
.M &;!%.
M" M% !
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%-.""!"7=%&
 ".! !:Q#4=I<%&-
=%%>@" :
QIIAI42% ""!9I2R%-"<#
 !"
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.         $ME    .M(-
+M7"  
+(??=-"M.. .576 #2 A
+(??=M+  =A  .696 2
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 ."!&G2R
3 ."!%- !!&;""
 "-% G .QGI
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
#
+(??=(-.!+" =2G 2 .707
+(??=(-.D%'  3 2I# #I
+(??= A =I .470
+(??=B # # A4
+7V1?=(% 4# .633 #
+7V1?=1   .809 A 2A
+7V1?=? ! #2I .451 ##G
+7V1?=. G .766 A4
+7V1?=+  A 2I .550
+7V1?=$ .880 2A2 =2A2
E( .812 =2 =22
(7" #I AI #4
?%. # =G #
*1 .675 =2G2 =2I#
*1$0 =23 -.465 =2
$SAbold#QI
$%
8% """&."
""- !A $%"&".
 "A .%%&0&
".!'..&0:A .
!C !%.'C
O)=.22GP". .% !"!%
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

""".A $%<( ".!
".&". !%&=." "&
"&""&0." %
 "& !%D=2X1. %!
+! "&& -!-%.%A
.0.""" .A "%."
&&... X1.&
A2Y%!. !"!.I5
'& ..$?(0% D$%
(:*?=G2=A#98 H<!&"% ."
D"A"M $!%!D"
&. %'."..!%.
%2AG!0:&*"F$22<
=!%:1<&34R% IR%
&  =!1&AR% IR%& 
(0&!0&.%'.
& :##GI4"!<%=% '
.&.! .'!!
%  ""..&
 " .&-.
!.%' -"&
 %.%  " - 
%&!1..:2#<.-
!.- "' . %
..&!- "
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
A
B&-  N!%'
 /.!":12<""
0.- .  %.'
!%%  " - !% "
!.& ".( ".
..0!&&.!'.-
 ":( 29!22</.%
&--..&;%'
+""!&"% "!-
 "% ."".!- "
..5&&  .  
%!1!-AR!% ":
0&%'<!.) !".
/.%'! ".
%D$%(!&!.&
";! 0- !&
 '".'% .-
#2=G2 .% :*.2A<
.%."4.:?ZD2<!%
""&."% .- "
*."%"% '!& @ "!
.%.!.!0.
%& @ ":"/.<&
.&&!!:& @ "<.
N!%& @ "& .&!&
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
I
!! %
& @' . :I<QG2W22B&.
 0&%&  "' .  ":
& !&.<&  : "5:4<
QQ39 "5:AG<Q#GQ42<..%
& &."& &% .%
!0..% &!&% 
 %' . % !9
!&&=. 
%  "!&!% 
.&.!'/.%% &
& &! .!-
'.:4<QII#W229. %
 ! %0!%%!
"% ./.!'
:<&% &=&-
&  %-). N
" %  "  "&
& !.% 
%% ...
Results
'()*!
)".@&" &."!
"'%.%0."&
"@" &.!"
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
4
"&"% % - !:(+((2<
.&." "&.
%="&  %.":!!F10
22I<':&;' . <
&" .);"% !.
"  ."./.!"% 
" - !%." 
 ":&&-"!!%."!%
 .<(%="=" &
 &" !%'
&.""../.
.&"% %!.."
&0%"/. .?!
.").%.
!.""&"
!"%"':
( 2<-.%".!
.:(."" !'<(-&;-
%--" &!
*%% %& .(&
""- "&. 
+),*)"'
.=&0&..""%.B&
&!D&. ".""@'
4!0&.! :B$< .=
:$<!!:!!F1022I<
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11

3
+"@'!: 5A#"M
$<.&;!% D:#<QG2
Q#4
?&.".@
&" !"!"'(:3<Q
G3Q22#-Q#  "@" 
!!".@'(:4<Q4#4Q223-
Q=3-&;5:(O2APQ3IQ3%%
 9(O2PQ##.A%" 9&
%.%-A
")?-"!!
%. "&%(-.
+M7"5(%=(-.+M7""!"
'(:4<Q4#3Q224-Q4&"=(-.
+M7"!"'(:I<Q2G2
Q22-Q=#'&""!!%=$ME
(:4<QI2Q2I-Q#9&%
"$ME(:3<Q#3Q2I-Q=%=
"=.M "'SA(&
%- %%""%!
.%
/%)!"'()
!
5 , .;"" "%G ..
!! .5(:4<QG2Q22#0QG%%= 
(:4<QI#Q2#0Q=#%"= 
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
G
' $ME.M(-
+M7"
    ((  (   
(  
(- 2I4A4=24G=2A2G
7" =2222=22 =2#2422
22
(%7? .32 9.28 .003 .31 6.01 .016 ##.27
7.38 .008
+7? =.29 7.37 .008 ,/12342=2G 
=.34 10.91 .001
(--(%7? =#23I4I=#A=3A#
=
(--+7?=A## =GI3=#A#
2222
#. %Q* %% I3(('%
A"9W2AW2'
"%=" "="
 D=B%"0
D&(-. !==A% A 
56? %""
 =D""& "
''. "%! !%
""/. ..""[
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
2
"C%=""!"
 :2#<%
 &!;(:I3<QAQ22-Q#2:8<
 . ";"'&
%.%%="(-.+M7"(:I#<Q
GG3W22-Q#:8*<$ME(:4<QAQ24-
Q:8E<.M %;
(:IA<Q#2SA-Q2A:81<)&.!.%
 (-.+M7":8*<&&D
 !;(:42MI3<Q24#GQ22W22I
)/.;% '
!  ' 
& 8% [
.! "[ '&
 4"M $GR:#A3"M $<9:G<Q
GQ228[.&"&! 
6 ) "D"!B%&
" "&!&%" 
&'%.%.0$&%
&" "&!%" 
& ':'<%.%.
0
.  .%.%&
!!.%& @ "% @ "&&!
. !0&.&. "% 
&"% -=";!8 %=""!
.(:I<QA4AW2G0Q#(-.+M7"(:I<Q
IAW2#0Q#;!"'9%$ME
%%;(:I<QGW2G0QI8
& .& 5'5(:A<QAGW230Q#9(-.
+M7"5(:A<Q2W220Q#39$ME5(:A<Q4
W0Q" !.&".& "% 
%& !&"% . !0
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

!&[ '& =42"M $
#R% 9:2<Q3Q2I34
')
";%="=" "'
"%E! %. "!
%="=" "!?%%
 "; "%="=
"!!Q4I###"!W23
(()!"7+'.
-D=
7 8!&'!&!"%  
+&%!&
"" N!%& 
484
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33
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

8*'
(%="%" !
"!&%""&0
:<QAIW22!&""!
&@:<Q=W22:>*@
!&>@:I<Q=IW22<?
- .>@"%"
 :..""% <
%&0 %N.%;!"
'(:<Q##AQ242-QG? ..
>*@%" >*
@"'(:<QQI-
Q=2""!C &"&
".-"
)%
)- &%="=" 
" ',0%'& 0";
"%! !
!. %-.%!0%.
" %&-"!?
&%.& &0
&=% . &!.%
:I3<QAW22.& :A2<Q23SA&
;%%"""'5
(:#<Q2#SA-Q2I%%=" 9(:#<Q
496
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520

#
222SA-Q=2%"=" ( !&
&"; "%"  
'' &"(:I4<QIG
Q2#-Q=2(('%%..
Study 2
Methods

+"&3.:I& 9 Q#9(*Q3<
..! ".&!"""
-. "&" 9
""&3 :(*QI 9 QG<
:7"&" ".%#4A [T#
!=!. &..%.%
!<+"&...&
.!..&""%.!80"9
""&..! N!&""
4GR%% """.% " %
.! '';!%.%
".:<Q=AQ33:2<QAIQA4"!
1%".."&

+.& %(.!&&-"
 "!"&""&.
 "%""$0".(.!:<%"
% "" "%/.!
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

".& ":TA $<&
&.."9:<!&0
 2= ..=0""(.!9!&
00.K&!!.""!.&!
&!."&!.&!.!.
"&."!.&!&!.".!"
&!.L9:<! ""0%
/.." 
"9:<A .%/.:A
.%%.=0<!"
 ":TA $<."&.9:<!.
 ":TA $&.<."&0&0
? !%" "&%D=2X1( "
&""!B 7".!$
*" %"!,!%&-+! "
&& -!-%.%A .0."
"" .(.!A "%."&
&... X1.&A2Y%!
. !"!.I5'
& ..$?(0% D$%(:*?=
G2=A#98 H<&!"% ."=!
=!%:1<&4R4R"!
&-"&%&5
8"" "B
""""."9%."N.  
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
A
""). ;"..&.
"" "%""."..
 "%T22.: "D<.&
"%"@" % ""% %
% "
(& %.!%" 
.& (.!8%= & :<
7"=(";? ?!:GG3<9:< .%
 E(:"% !F8!22I<9:< .
%%.&":(.! <9:< .%&.
&% "&!% "
.&.(.!8"@ & 
"="%7"=(";? ?!:
GG3<).% ..:GG3<"
"="%?.!"""%"@
 .!&"@%=" %.
QI/.& &:0=
. "! <
)-;"" "% % .&
!.(.!&-"#3R%%=
"="$"#%
 .! .0@%%.
 .&GAG& 
"%= ""= :
"!%<=:$D=(FE22I<
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
I
%%.&;"" "-% 
%"  .(.!:
.<&GGGIG%%="=""!B
 %" &.=
"% .!"!""+"
 ":D=<& ".%%="=
..." ! .%%="="
 3
1'9!" 5/
$
.        (%  +
+(??=-"M.. .656 782
+(??=M+  #2  .724
+(??=8..=' .592 .510
+(??=%  .760 .678
+(??=(-.!+" #33  
+(??=(-.D%'  #23 .502 
+(??= 2 -.598
+(??=B 561 .606 
E( .746  
?%. 587 
8 "%%%="#%%""@
 E.(.!- "&.
;"" """.%..
. "E.%="=%&! ".0
(.!.:<;"" " "&%.
-.!" %
596
597
598
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602
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614
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617
36
37
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39
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41

4
*1 .584  
*1$0 =#
$SAbold#QI
" "&%.%&." !;(.!
".(.!&'-:K L%
-&% Q2 Q<G&%="=
" ":<%="
" --)%&."&!
'%="=" 
"
Results
75 '
'& "..." !. 
. "& %""- 
%'% 4""- 
.&.&#I#9 - .&I3A2
.&A(*%  :A3(*-..<
.! !&.%   %;
 "%.?!!.0!C.
.B&-.!'.%
&II:(*QA4<G:(*QI2<"M $%"=.=
9 ".  %%=""!"
 & %% % &&
-."".&  & 
!% & .! "!
 "D:N.## #& <&-&:
<%- 0&-.
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
3
 ""!'A#"M $:(*QG<
) @'&I3G"M $:(*QG< @&
AA"M $:(*QIG4<
)')!"
*" ! ";(.!".(.!\:
1&(.!"!&%=" 
;!"'(:2<Q2Q2#30Q3(
" "!--&
;-.%%  .!
.:0Q4Q23<
)/.;%&%="
 '!  '
 "!& 
"!8.! ":(*
 < '& I2"M $#R
:IG"M $<9:2<QIQ228.
&"&! !&:(*&
< '& =2"M $=;R
% 9:2<Q=QII
)%="=" &"!
;%"=  (:#3<QGA
Q230Q=#2N.(.!(%%= &
".%%!;(:#3<Q#Q24G0
QA-.%.%& &.. "
;!!58%=""!0
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664

G
Q4=#2"!Q2I2A-.%"
&-.  !58%="0
Q=4"!Q22
2%)!"'()
! 5/

        (    (  
(-  2222 =2 2I
7"  =2A#3 =2I G
(%=+? *"! .18 4.40 .038
(--(=+*"! =2 
(%?   /; 12<=
+?   =.30 4.95 .028
(--(%?   =2I #
(--+?  =2 22 
#7."%%. % !%=
""!" "7."
%. % !%" 
"" ""%Q2#3
"!A"9W2AW2'
-":=% <%=" 
"=" D=B
%"0D&
)%
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689

#2
(.!'&%
.& &0&=
% . & "% :<Q#Q3
& :2<QQ29!:G<Q4Q22(.!
&;%" "
'5(:<Q2GQA3G0Q2I
Combined Analysis
.%(.!"." ! ""
 % (.!9."!&%="=
" "'.'
"0&"".."%
.&&! "
 :(.!" <%" 
 (.!;&!%"@ 
* .0&"!%
&'"@ %
"&'%= \&=
"&.:"&Q32R<!;!32R% 
&%= '(.!&
"&Q24G
-&.%&.
!".""%"&.!
 .?!&:<"%="=
 &. ..!"D=9
.. ":%."
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
#
<9:<%.!)" --
" -.!&!&.
.&%"!%%="=
"(.!
7."A0!; 5
8-".%=""!"
  (:A<QA#3Q2-Q2:"
. % "!<2
(&%="=" &
"!  58%(:I2<QAQ22-
QG9%"(:I2A<QGQ22-Q=G?%
%="=" &""!
 .
.!- %%=
"=" &'8-S
#8.!SI!&
%.%" .%" &
 &""" :%="<
"". ":.,(&!<-8...
!-"" 
8!&.!!&"
&=&
""-%= 
"-"=  ;
10 )=!""2& % (.!& "="=.=
0'&!.!0%=""!
"  .(:2A<Q#4Q222#-Q4
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
#
&!5(:3#2<QSA-Q=2(:3G<Q#GSA-Q=2
"!
;%)!"'()
! '%955/

      -  (   - (  
(.! =2 2 22 22
(-  =22 22 =2 2
7"  =2# 4 =2# 
(%?   .29 11.25 .001 .26 9.36 .003
+?   =.29 11.91 .001 -.30 12.55
<.001
(.!-(%?  =23 #
(.!-+?  =23 
(--(%?   =23 GI
(--+?  =24 I4 
7-(%?  =2 
7-+?  =2 #G
#. %Q* %% 4I2G
A"9W2AW2'-"
%=" :=% <"="
 D=B%"0
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
##
D&(.!==A(.!A(.!(-&
." .!:""(.!<
Discussion
?&" "J%."%.
 "J= '!..
".!&"%"@"
 1&."'.=
&0&"!%.@&"
 .!&%"@" 
!+&%" 
&;"%'."&."
 % .N
?(.!&!D% &0"%
%% "/.&;.
 ." !!J"%>@"!
"'"J&!=;) "D
.."/..%&0
& ."'V.";"%
" !0!. %
 ".N%"=.=

,0 N!%".;'. 
&;;&'"@
" .!+"@' .!
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
#
."%! C.!. %
:%...C-.
.  "0"%"<
)& "!-.%'
"!. "&&0!50!
&;' . &.=
& ".%.""@"
.8' !"
%&"%'" ! !  '
"-""" ( !0
:2<%.;&'".
' ".0%%"
 
+ % .'"
." ".. "
:02<-.%= .:Z2A<
>& .@% .":B=$.223<
 .0"":.GGG<'.
;.0.@"&"
'"..".!%"
8. !.&0%0
'"!%....D .=
0 !&" 0%..
"'"
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811

#A
8!. ".!%".
;:'"(12A<&'
".!:1 F1..2A9$
2I<&.%.".%. ;& "
% ..&'.;! 
;&&.%.".J 
% >".!@;..D%
""&B& ="&%.!"
 !"&."
>")"?
'."".."& %=.
%'".& "[K1 1L
KE%L [&&;.""%
"%"/.!  "!
!'"& %"
.7"'"%%
&":( 2<"@"
 :!22<&" &.
".'@&  &
.!%"N!% . "
'"?"%! - !&"
%."."'
+!..""% ". &%
.""K?%!?L  .'
 7""'=
812
813
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816
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818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836

#I
" KL&!%".
%" "[ K?%!L[.
"&[ K?L
.!!.%"!%' 
"."0&"-["" 
! =%"?%!?!"
8  @"%&"..
%  ..%@&=!
" ?%%% 0
 . &7
."!".%";
![";!%
' !"!& ".
".%&"D
'..?"%?%!?
!"%'  !.
.-"!"&!
?...!'&&."&
"?%!?!" !-";
.-.!.J""!"
""&!%"%J
!%':DD22I9) 2#<
 %&'""%
. \+")""%..&0.
"!?%!? -"&!".
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
#4
. ".%'&"
1 1E% """-"
))
..!!"0&'"!
""'."" "&&
. "'%. .&! 
:E 29. F(D22G<[".&!
!";@?%
0&-&'"!:% 
 !.< 0-'
 .:("2<
. &.!".!&!.
&"";.'%'
. %KL";": .
"% ""%%
<8.. !"-
&'"
)6)
?-"!!%(.!&"@-.
"&%.".!"%'E!
"@."'? !"% 
0-.!"!%'"!.'@
-.%.":E&F1 2<)
 "%(.!.%9%..
 !&;.
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
#3
'
'.%! "&-"!7;
%.%.- ":12<?!
. -> -%&.
. .@'.".%!&.
 "&.-"D"!&
.0&=.!&'! 
:4R<:4AR<.""'.".!
. ..! .." !
 %':12<&!:W2R<
1..:2#<..- "! H
! &;% .- "&
&:!229( 2<!
.&!= '.! .
- ""-!& !
:02<;&.""
.' "&"!?%.'
! ;. .0&.&.%

' &"...!$0
! . .!"""N!
. ! ".:. F
(D22G<'..- ""%'!
)0&""N%'.
& ...
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
#G
- '"%. .""
!&% &0%. 
C. 0 &
""9 !%. ."
. %! :"".< ..!
   "0&.&0& .&
!."".;"0
!!""
Conclusions
-!%;"'"!"!
"KL["!!
 "%...%.% "=
".!=.''"!&
  "=. "!&
"! "!"J.
")&. !
?%!?B!"!"!%..
!% ".& =
%"%"!' !"
..!"&!"
." :2<
Author Contributions
()".!".
..@$'()
"% ()"%  !
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
2
!"()% ."
."."";
% ."%. 
Acknowledgments
 ."&0.""!(
8..78&":*=32I9%&"<
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

References
E 7?E=1(B0Z.!.EE+2
-!"-8E.3
E&+1 2%-! 
"!B EIII[4I
E++0""ZE.]7=B0Z2.%
 ."". = 5&
% .8.##4[#A
110Z221"57"
"/.!"Z+(+!GG
43=2I
11) Z7)*?7GG'-!
H(IA2=
11(GG3."" 
+!.#44G=33
11(2'-!"&!.%. 
.7+!IA4[#G
1"EZ2A'-!. E7
G2G=#2
1&!)7 )GG. .%-!
7###=IA
*.(B.7"FD(
B:2A<(!'-!1%&?
 %'-!5*.=E1='(.!5
:<2A2
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949
950
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952
953
954
955
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957
958
959
960
961
962
963
964
965
966
967


Z77E...E  "C(
Z.0EE'ZB Z. ?*2A(!
-!".-.%= .
%((57.'-!1:7'1<
.!+!.I#3=#33
*DE(EE ,B22G
?-!" ..
.."CE+!!IA43=4#
&0+)80Z2.! 5 E
8.%'.!1!"+(
+!E.#34=3
EZGG3+=(";? ?!5.!
"". Z+II#3#=
8 7?^!=('2"" 
!.!-!"=%!!5
 "%. *(4A[I
8177GGAB "!.%%
!.V7E42=A
8Z( "Z 222 . %"
"/.! "5; !%!
""+(+!E.I#2=#A
8E)^.Z7Z(+0(*22A!
-". &.""
%.+(24#4=42
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
#
$*).D&1)21
8"!.. 5%=.% !
%". ZB. E#I2G[2
()="172#) @
.="-.""!%.%--.!
+!(2I[2
&(( Z$122A%"
.""-!""".
%%& "+! I4A#=A#3
&*"7$122%" 
!-!"% .% %
%+!"!4IA=I#
B=$.ZE  )$1223?C.%K& 
.L.""   ."
 .!".-!" !
+! 42G4I=G3A
B=$.ZE  )1$127"/.!
-!5?C.% ;"%"Z(
+7#4=G2
B=*(&DEZ
22A'-! 0& .!
 .!+!E3A=3
0222'-! -"+!(=
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
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!*!*10)$22I*!*!.%+
&H0
$$. 'F0ND02I?+.
EE.?'-!7B. \'"
8*&%'$!Z.3
$1&F Z22A%/.".
-!0&".
" ".& E+!IGA=
$D=(,FEZ822I.0@1.1
%.-%% !A4[I
1..1.+(DZ2#+ &
.""-!5-!. 
.\.E7#43A=G
DD*'E*E(.817.+
8E$8$?+**
$.'$*22I1+" !5
"&-!-!%  1
+" BI[I
1 1F1..2A*-!.
. \&%+"+!(244=43G
. (D*(22G""&
" .! % %
8.#2I=I
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038

A
. H.$2I.  % =%
"=5(  "B 
E44G3=
'_1E+222(+((((" % . %
 "."!_+E7
?. 1 ".##GI=2
'"(12A ".!%"!
(#G4I
+1F+ZG4G?.% 
%. %-!+
(4IIII=IIIA
( ?=! H^!=('F8 72
..C.&"@ "C
".% (.G
##4=#A
( ?^!=('$0 Z88 72'-!
.%  5."@
"!+!.#444[3A
( "Z7)(+"*GGI1C"5
 ""Z+(+!43GG=G
( (` E8Z22".%
-!! "=
" 1-"B EA4AA=I
( ),EDZB01 "77
& Z$12#%."
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
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1059
1060
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1062
1063

I
"/.!" -!.!5
 "; ?Z%
+!"!.334[3
("(*0E0E(a%$(&
7.Z)B. 72'-!%"
" . +(2G
3=3G
0E1..(DDZ1+2
'-!-%&" 
& +!.#IA=
!18!7122I.%.&"5
 ""Z+(+!G243=G#
!($1$&E+.&$..7,"
Z222E"% 5==%
;==C+!724=G
!(22I%%.
1.*+!(A4#=44
!(("=E(( 22" -!
& " "  0%"=
"\+!(#=4
.7 .1"E.GGG+ !
" -! !& 5
 "+!!IG4=#
1064
1065
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1067
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1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086

4
,=+22A'-! %=&=
&^+! 
+!AA4=32
(!$.+b2(M+"!%
(E5?"""%%!
-+!.#IIA[4A
?ZDE77&E0 =
.Z2!%-!" 
.% 8.I4
) '^!=('( ??8 72#
+ -!.%&  
=";&-!+!.#3IG[42
).7)+.N;DB(&D*E
11(22G*%!-!& 
*+!A#I4=#4#
) Z7?7B.1711(GG'-!
 !%% %""%
% ":.<Z.%.I4[
A2
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1100
1101
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... A recent longitudinal study on the parent-to-peer attachment transfer (Umemura et al., 2020) indicates that most young adults make the transfer within the first year of their romantic relationship, albeit cross sectional studies indicate a longer timeframe of around two years (Hazan and Shaver, 1987;Freeman and Simons, 2018). Observational studies assessing peripheral OT (i.e., plasma assays) among individuals in single, new, and long-term relationships have documented higher circulating OT among adults in new relationships compared to their single (Schneiderman et al., 2012), and long-term counterparts (Grebe et al., 2017). As such, we expect romantic relationship duration to moderate OT effects on closeness to partners and others. ...
... c intensity and engagement experienced by most couples in the first year suggests a sensitive period in which bottom-up processes are more involved in promoting relationship specificity and exclusivity (Acevedo et al., 2020;Aron et al., 2005;Fisher, 1998). Indeed, observation studies show that circulating levels of OT diminish as relationships age (Grebe et. al, 2017), and the dopaminergic system is believed to be most active in early-stage relationships Takahashi et al., 2015). To date, studies have not established whether relationship duration moderates OT effects on partner preference, which is a focus in the present investigation. In addition to relationship duration as a potential moderator, mou ...
... Relationship duration was assessed in the screening survey and then adjusted by adding the time between the screening and the first lab visit, with the following distribution: 4-6 months (10%); 6-8 months (5%); 8-10 months (5%); 10-12 months (5%); 12-18 months (22%); 18-1 year (10%); 1-2 years (25%); 3-4 years (12%); and More than 4 years (6%). Given that most young adults reach the "clear cut" phase of romantic attachment formation within the first year of a new relationship (Umemura et al., 2020) and that circulating levels of OT are higher in new romantic relationships (Grebe et al., 2017), duration categories beyond two years were collapsed. To emphasize the importance of differences in duration during the first year of the romantic relationship, duration was entered as an ordinal variable in all analyses. ...
Article
Animal studies confirm oxytocin’s (OT) role in regulating monogamous sexual behavior in pair-bonding rodents; and human studies are beginning to translate how this highly conserved neuropeptide is implicated in romantic attachment formation. A number of studies have shown how OT promotes relationship exclusivity by diminishing interest in strangers and increasing reward response to partners. Less clear is whether these effects are modulated by romantic duration or life history factors, or if OT’s social distancing effects generalize beyond strangers to close relationships. We report the results of a double-blind, placebo-controlled crossover study on the effects of a single dose of intranasal OT (24 IU) on forty-four young adults (91% female) in different stages of romantic attachment formation (M duration=21 months). Participants completed a screening survey and two lab visits separated by 4-weeks, including a diagrammatic measure of attachment to parents and peers, attitudes related to sexual conservatism and partner infidelity, ratings scales of closeness to romantic partners, and visual attractiveness ratings of strangers. Individual differences were examined by life history factors, including maternal love withdrawal and parental separation. Results indicated that OT administration decreased attachment to mothers, decreased attachment to subsidiary attachment figures, and decreased attraction to strangers. In all cases, emotional distancing was stronger among participants in newer romantic relationships. OT increased arousal to partner infidelity and increased sexual conservatism among participants with negative life history experiences (parental separation and high love withdrawal), whereas the reverse was true for participants reporting a more positive life history. Findings suggest that OT supports exclusivity through social distancing from strangers and close others within a sensitive period of attachment formation. In addition, findings indicate OT plays a different role in mate retention strategies by life history.
... However, the findings were mixed. Two studies indicated positive correlations between peripheral OT level and behaviors of attachment insecurity (Daigle et al., 2020;Vittner et al., 2019); seven studies showed negative correlations (Algoe, Kurtz, & Grewen, 2017;Atzil, Hendler, & Feldman, 2011;Bick & Dozier, 2010;Gordon, Zagoory-Sharon, Leckman, & Feldman, 2010;Grewen, Girdler, Amico, & Light, 2005;Markova & Siposova, 2019;Ulmer-Yaniv et al., 2016); one study reported opposite patterns between females and males (Markova, 2018); and ten studies did not detect any significant relationship (Apter-Levi, Zagoory-Sharon, & Feldman, 2014;Bick, Dozier, Bernard, Grasso, & Simons, 2013;Elmadih et al., 2014;Feldman, Gordon, Schneiderman, Weisman, & Zagoory-Sharon, 2010;Gordon, Pratt, Bergunde, Zagoory-Sharon, & Feldman, 2017;Grebe et al., 2017;Lebowitz et al., 2017;MacKinnon et al., 2014;Miura, Fujiwara, Osawa, & Anme, 2015;Taylor, Saphire-Bernstein, & Seeman, 2010). Such inconsistencies possibly result from smaller sample sizes, methodological shortcomings in obtaining attachment measures, and unspecific confounders of individual differences (e.g., emotion statement, relationship quality, and educational level). ...
... Among the 20 studies, 16 assessed the behaviors of mother-infant attachment such as mother-infant interaction and paternal affectionate contact (Apter-Levi et al., 2014;Atzil et al., 2011;Bick & Dozier, 2010;Bick et al., 2013;Daigle et al., 2020;Elmadih et al., 2014;Feldman et al., 2010;Gordon et al., 2017;Gordon et al., 2010;Lebowitz et al., 2017;MacKinnon et al., 2014;Markova, 2018;Markova & Siposova, 2019;Miura et al., 2015;Ulmer-Yaniv et al., 2016;Vittner et al., 2019), and four measured the behaviors of romantic relationship such as romantic bonding and affectionate contact (Algoe et al., 2017;Grebe et al., 2017;Grewen et al., 2005;Taylor et al., 2010). According to the classic attachment paradigms (Ravitz et al., 2010), including the Strange-situation paradigm (which measures personal distress from separation with caregiver and the signals for resists contact upon caregiver's or immediately calms with contact; Ainsworth, Blehar, Waters, & Wall, 1978), Adult Attachment Interview (which measures parental behaviors of loving, rejecting, neglecting, involving, coherence of discourse, fear of loss, and passive speech; Hesse, 2008), and Current Relationship Interview (which measures partner's behaviors and thinking about attachment-related issues and discourse style; Crowell & Owens, 1996), behaviors of attachment insecurity in these studies were systematized: Negative J o u r n a l P r e -p r o o f statement in romantic relationship was directly used as attachment insecurity (Taylor et al., 2010), and positive interpersonal interactions (e.g., parent-infant interaction and constructive communication of romantic couples) of 19 studies were reversely transformed as attachment insecurity (Table S2 in Supplementary materials). ...
... Thirteen studies reported effect sizes as r values, and seven studies showed effect sizes as F value of repeated-measures ANOVA (Bick & Dozier, 2010;Bick et al., 2013;Lebowitz et al., 2017;Miura et al., 2015), or t value of paired t test (Elmadih et al., 2014;Feldman et al., 2010;Grebe et al., 2017). We transformed the effect sizes as r values (Table S 2 in Supplementary materials). ...
Article
In light of the roles of oxytocin (OT) in social bonding and interpersonal relationship, studies have examined its roles in human attachment, but by and large previous findings are inconsistent. Here, we conducted three meta-analyses to estimate the associations between peripheral OT level (e.g., blood and salivary OT) and attachment (i.e., attachment dimensions and behaviors of attachment insecurity) and the effects of intranasal OT administration on behaviors of attachment insecurity. The analyses indicated that: (1) Peripheral OT level was not significantly associated with attachment dimensions (e.g., attachment anxiety and attachment avoidance) and behaviors of attachment insecurity; (2) intranasal OT administration significantly reduced behaviors of attachment insecurity of neutral contexts, particularly attachment avoidance. The findings suggest that intranasal OT administration is an available approach for reducing behaviors of attachment insecurity of interpersonal situations with ambiguous social cues, which implicates suggestions for therapeutic treatment of attachment-related dysfunctions.
... Previous studies have found that unextracted plasma oxytocin levels are higher than the extracted ones (Leng and Ludwig 2016) and hence, researchers pointed out the necessity to measure oxytocin levels with the extraction step especially in blood oxytocin measurement (Szeto et al. 2011;McCullough et al. 2013). However, since the levels of salivary oxytocin are low (McCullough et al. 2013), the extraction step discards oxytocin as the minimum detection limit of the assay kit and induces a high intra-assay coefficient of variation (CV) causing unreliable results (Grebe et al. 2017;MacLean et al. 2018). Conversely, Carter (2014) has argued that the extraction step possibly discards most of the oxytocin, thereby underestimating its levels, since oxytocin is filtered by binding to other molecules in the plasma, the problem which was also pointed out in salivary oxytocin level measurement in another study (White-Traut et al. 2009). ...
... Therefore, examining the salivary oxytocin effects on different subregions of the amygdala could provide a better understanding regarding the mechanism of the association between salivary oxytocin with amygdala. In addition, this study assessed salivary oxytocin levels by ELISA with unextracted samples, which has been questioned because of the possibility of a furor for the result (Szeto et al. 2011;McCullough et al. 2013) but is widely used in salivary oxytocin study due to the low oxytocin level in saliva (Grebe et al. 2017). In the future, measuring salivary oxytocin levels using the extraction method could help replicate our study findings and increase the robustness. ...
Article
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Salivary oxytocin levels have been widely measured and studied in relation to social behavior because of procedural simplicity and noninvasiveness. Although the relationship between oxytocin levels in the blood and the hippocampus and amygdala is now becoming clear with reliable blood oxytocin studies, few studies have examined the relationship between salivary oxytocin and the brain function and structure. This study aimed to investigate whether the salivary oxytocin level is associated with the volume of the amygdala and hippocampus in 178 adults (92 women and 86 men) in their third to seventh decade of life. We performed volumetric analysis of the amygdala and hippocampus using FreeSurfer and measured salivary oxytocin levels using enzyme-linked immunosorbent assay. The results showed contradictory effects of the salivary oxytocin level on the amygdala volume by sex and no significant effect on the hippocampal volume. Specifically, men showed a positive correlation between the salivary oxytocin level and amygdala volume, whereas women showed a negative correlation between the salivary oxytocin level and amygdala volume. The present study’s finding of sex differences in the association between salivary oxytocin and brain structure supports previous findings that there are sex differences in the oxytocin system.
... A recent study found a high correlation between extracted and unextracted oxytocin levels in dogs, which demonstrated the validation of measuring without extraction in saliva methodologically [35]. Moreover, measurement using the extraction step is capable of inducing a high intra-assay coefficient of variation and unreliable results [35,36]. Therefore, some recent studies [36][37][38] have used unextracted oxytocin samples to measure the oxytocin level and have examined the relationship between oxytocin level and human sociality. ...
... Moreover, measurement using the extraction step is capable of inducing a high intra-assay coefficient of variation and unreliable results [35,36]. Therefore, some recent studies [36][37][38] have used unextracted oxytocin samples to measure the oxytocin level and have examined the relationship between oxytocin level and human sociality. ...
Article
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Studies on the association between trust and oxytocin, a neuropeptide of the central nervous system, have not reached a consensus, thereby challenging the possibility of a direct association between the two. However, previous studies have not examined how oxytocin is correlated with trust, based on its categorization into different factors in the field of social science. For instance, based on Yamagishi’s trust theory, trust can be categorized into two factors: general trust and caution. General trust refers to beliefs about the trustworthiness of others, whereas caution refers to the belief that caution is needed when dealing with high social uncertainty. In this study, to examine the relationship between these two factors and oxytocin, we analyzed data of 197 adults (men = 98, women = 99; mean age = 41.7 years; standard deviation for age = 10.4 years) and examined the relationships between these two factors of trust and endogenous salivary oxytocin levels. We found that oxytocin was positively correlated with caution rather than with general trust thereby suggesting that oxytocin plays a role in regulating caution rather than general trust among the components of trust. The present study demonstrated that salivary oxytocin level can act as a biomarker that partially predicts one’s trust, especially as reflected by caution.
... Although Carter (2014) has not mentioned about oxytocin in saliva, another study has pointed out that a similar problem may arise with oxytocin in saliva (White-Traut et al., 2009). Furthermore, since the levels of sOT are low (McCullough et al., 2013), the extraction step discards oxytocin as the minimum detection limit of the assay kit even after concentration and induces the high intra-assay coefficient of variation causing unreliable results (Grebe et al., 2017;MacLean et al., 2018). For those reasons, unextracted oxytocin samples have been previously used to measure the sOT level in ELISA assay and examine the relationship between oxytocin level and human sociality (Grebe et al., 2017). ...
... Furthermore, since the levels of sOT are low (McCullough et al., 2013), the extraction step discards oxytocin as the minimum detection limit of the assay kit even after concentration and induces the high intra-assay coefficient of variation causing unreliable results (Grebe et al., 2017;MacLean et al., 2018). For those reasons, unextracted oxytocin samples have been previously used to measure the sOT level in ELISA assay and examine the relationship between oxytocin level and human sociality (Grebe et al., 2017). Therefore, in the current study, we used unextracted oxytocin samples. ...
Article
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Spirituality and religiosity have a significant impact on one's well-being. Although previous studies have indicated that the neuropeptide hormone oxytocin is associated with spirituality/religiosity, existing findings remain inconsistent. Some studies have reported a positive relationship between oxytocin and spirituality/religiosity, while other studies have reported a negative association. Herein, we examined the association between endogenous oxytocin and spirituality/religiosity in 200 non-Abrahamic Japanese individuals (102 females, mean age ± standard deviation = 41.53 ± 10.46) by measuring the level of salivary oxytocin and spiritual/religious faith. We found that the level of salivary oxytocin was negatively associated with spiritual/religious faith. Individuals with higher levels of salivary oxytocin tend to have more negative spiritual/religious faith compared with those with low oxytocin levels (e.g., “ Spirituality/religiosity makes people passive and clinging .”). Moreover, this tendency was only significant in individuals who were not interested in a specific religion. The uniqueness of spirituality/religiosity in Japan could help interpret the current findings.
... SD = 5.37 years) to participate in Study 2; at least one member of the couple came from a psychology student subject pool at University of New Mexico. This study was designed to investigate relationships between several physiological biomarkers and aspects of participants' romantic bonds (a separate component of this study was reported in Grebe et al., 2017). All participants reported being in an exclusive romantic relationship with their partner lasting at least one month; the mean reported relationship length was 24 months (SD = 23 months). ...
... All participants reported being in an exclusive romantic relationship with their partner lasting at least one month; the mean reported relationship length was 24 months (SD = 23 months). In total, 33 women were naturally cycling, 38 used some form of hormonal contraception, 1 had undergone a hysterectomy, and 3 did not report this information (see [Grebe et al., 2017]). ...
Article
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Oxidative stress is a physiological condition in which reactive oxygen species created through cellular respiration can potentially damage DNA and tissue. Oxidative stress may partially mediate trade-offs between reproductive effort and survival efforts. On the one hand, traits associated with reproductive effort, particularly costly male-male competition, are expected to raise oxidative stress. On the other hand, behavioral strategies may be a critical mediating mechanism, such that those who can better resist the physiological costs of oxidative damage exhibit increased mating effort. In a sample of 248 college students (173 men), we examined the associations between traits linked to mating effort—including personality features, athleticism, and history of illness—with levels of 8-OHdG, a biomarker of oxidative stress. 8-OHdG was measured twice, one week apart, once during active hours and once at awakening. In men, surgency, social dominance, and athleticism were all negatively associated with 8-OHdG levels in awakening, but not lab samples collected during active hours. In women, these same traits were positively associated with 8-OHdG levels, particularly in morning samples. Differences in associations based on sex and time of collection introduce additional complexities to understanding links between oxidative stress and mating effort.
... OT levels were measured using commercial OT-ELISA kit (Enzo Life Sciences, Farmingdale, NY, Catalog #: ADI-901-153A) in the Comparative Human and Primate Physiology Laboratory at the University of New Mexico (directed by Melissa Emery Thompson) using methods previously reported (Grebe et al., 2017). Briefly, samples were thawed, vortexed thoroughly, and centrifuged for 15 min to break up and precipitate mucins. ...
Article
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Background. Extensive research has evaluated the involvement of the neuropeptide oxytocin (OT) in human social behaviors, including parent-infant relationships. Studies have investigated OT's connection to human attachment to nonhuman animals, with the majority of the literature focusing on domestic dogs (Canis lupis familiaris). Utilizing what is known about OT and its role in maternal-infant and human-dog bonding, we apply these frameworks to the study of human-domestic cat (Felis catus) interactions. Methods. We investigated changes in salivary OT levels in 30 U.S. women of reproductive age before and after two conditions: reading a book (control) and interacting with their pet cat. Participant and cat behavioral patterns during the cat interaction condition were also quantified to determine if differences in women's OT concentrations were associated with specific human and cat behaviors. Results. Our results revealed no changes in women's OT levels during the cat interaction , relative to the control condition, and pre-cat interaction OT levels. However, differences in women's OT concentrations were correlated with some human-cat interactions (e.g., positively with petting cat and cat approach initiation, negatively with cat agonistic behavior) but not all observed behaviors (e.g., use of gentle or baby voice) coded during human-cat interactions. Discussion. This study is the first to explore women's OT in response to interactions with their pet cat and has identified distinct human and cat behaviors that influence OT release in humans.
... Consistent with the ACM, upregulation of OT pathways has been implicated in multiple traits expressed by individuals displaying slower life history strategies. Converging lines of evidence support a role for OT in maintaining the relatively high levels of human maternal (and paternal) care (reviewed in Feldman & Bakermans-Kranenburg, 2017;Scatliffe, Casavant, Vittner, & Cong, 2019;Szymanska, Schneider, Chateau-Smith, Nezelof, & Vulliez-Coady, 2017); in maternal protective behavior (reviewed in Bakermans-Kranenburg & van IJzendoorn, 2017), from human mothers actively protecting infants against strangers to rodent mothers carrying out offensive attacks against intruders; in supporting more cohesive and enduring sexual and romantic relationships and guarding them against threat (Aguilar-Raab et al., 2019;Grebe et al., 2017); in enhancing ingroup, but not outgroup, trust (Van IJzendoorn & Bakermans-Kranenburg, 2012); and in supporting human longevity, health, and vitality (Carter et al., 2020), all of which are indicative of slower life history strategies (e.g., Belsky et al., 1991;Del Giudice, 2018;Ellis et al., 2012;Figueredo et al., 2006;Zhu, Lu, & Chang, 2021). These data, together with the tentative evidence from our literature review correlating early-life stress with down-regulation of OT-system parameters (e. g., methylation of the OXTR gene, blunted secretion of OT in peripheral fluids, reduced responsivity to exogenous OT), particularly in community-based samples, highlight the potential mediating role of OT in shifting individuals growing up under harsh, unpredictable conditions away from a slower life history strategy-and toward a faster one. ...
Article
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Despite evidence supporting a role for oxytocin (OT) in regulating social behavior, surprisingly little is known about how this neuropeptide is calibrated during development. We systematically reviewed empirical studies in humans (k = 86 publications reporting on 66 independent samples; N = 7319) that examined associations between early-life stress and three OT system components: endogenous OT, methylation of the OT receptor gene (OXTRm), and biological and behavioral responses to intranasally administered OT. In a series of meta-analyses, we found some evidence that both children and adults who grew up under more adverse conditions tend to have lower endogenous OT (r = .12 and r = .09 respectively), that early adversity is associated with higher levels of OXTRm (r = .02), and that adults who report lower levels of childhood adversity tend to show more positive responses to intranasally administered OT (r = .12). These results were found in typical populations, and were in most cases absent in clinical samples. We discuss these findings in terms of both the prevailing medical model (focusing on the harmful effects of early-life stress) and the adaptive calibration model (focusing on developmental adaptation of biobehavioral systems to early conditions) and suggest that an adaptation-based approach could meaningfully advance research and intervention on the sequelae of early adversity.
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A prominent body of research spanning disciplines has been focused on the potential underlying role for oxytocin in the social signatures of monogamous mating bonds. Behavioral differences between monogamous and non-monogamous vole species, putatively mediated by oxytocinergic function, constitute a key source of support for this mechanism, but it is unclear to what extent this hormone-behavior linkage extends to the primate order. In a preregistered experiment, we test if oxytocin receptor blockade affects affiliative behavior in mixed-sex pairs of Eulemur, a genus of strepsirrhine primate containing both monogamous and non-monogamous species. Inconsistent with past studies in monogamous voles or monkeys, we do not find confirmatory evidence in Eulemur that monogamous pairs affiliate more than non-monogamous pairs, nor that oxytocin receptor blockade of one pair member selectively corresponds to reduced affiliative or scent-marking behavior in monogamous species. We do, however, find exploratory evidence of a pattern not previously investigated: simultaneously blocking oxytocin receptors in both members of a monogamous pair predicts lower rates of affiliative behavior relative to controls. Our study demonstrates the value of non-traditional animal models in challenging generalizations based on model organisms, and of methodological reform in providing a potential path forward for behavioral oxytocin research.
Article
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Animal studies confirm oxytocin's (OT) role in regulating monogamous sexual behavior in pair-bonding rodents; and human studies are beginning to translate how this highly conserved neuropeptide is implicated in romantic attachment formation. A number of studies have shown how OT promotes relationship exclusivity by diminishing interest in strangers and increasing reward response to partners. Less clear is whether these effects are modulated by romantic duration or life history factors, or if OT's social distancing effects generalize beyond strangers to close relationships. We report the results of a double-blind, placebo-controlled crossover study on the effects of a single dose of intranasal OT (24 IU) on forty-four young adults (91% female) in different stages of romantic attachment formation (M duration=21 months). Participants completed a screening survey and two lab visits separated by 4-weeks, including a diagrammatic measure of attachment to parents and peers, attitudes related to sexual conservatism and partner infidelity, ratings scales of closeness to romantic partners, and visual attractiveness ratings of strangers. Individual differences were examined by life history factors, including maternal love withdrawal and parental separation. Results indicated that OT administration decreased attachment to mothers, decreased attachment to subsidiary attachment figures, and decreased attraction to strangers. In all cases, emotional distancing was stronger among participants in newer romantic relationships. OT increased arousal to partner infidelity and increased sexual conservatism among participants with negative life history experiences (parental separation and high love withdrawal), whereas the reverse was true for participants reporting a more positive life history. Findings suggest that OT supports exclusivity through social distancing from strangers and close others within a sensitive period of attachment formation. In addition, findings indicate OT plays a different role in mate retention strategies by life history.
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The neurohormone oxytocin (OT) has been one the most studied peptides in behavioral sciences over the past two decades. Primarily known for its crucial role in labor and lactation, a rapidly growing literature suggests that intranasal OT (IN-OT) may also play a role in humans’ emotional and social lives. However, the lack of a convincing theoretical framework explaining IN-OT’s effects that would also allow to predict which moderators exert their effects and when, has raised healthy skepticism regarding the robustness of human behavioral IN-OT research. The poor knowledge of OT’s exact pharmacokinetic properties, crucial statistical and methodological issues and the absence of direct replication efforts may have lead to a publication bias in IN-OT literature with many unpublished studies with null results lying in laboratories’ drawers. Is there a file drawer problem in IN-OT research? If this is the case, it may also be the case in our laboratory. This paper aims to answer that question, document the extent of the problem and discuss its implications for OT research. Through eight studies (including 13 dependent variables overall, assessed through 25 different paradigms) performed in our lab between 2009 and 2014 on 453 subjects, results were too often not those expected. Only five publications emerged from our studies and only one of these reported a null-finding. After realizing that our publication portfolio has become less and less representative of our actual findings and because the non-publication of our data might contribute to generating a publication bias in IN-OT research, we decided to get these studies out of our drawer and encourage other laboratories to do the same.
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The use of intranasal oxytocin (OT) in research has become increasingly important over the past decade. Although researchers have acknowledged a need for further investigation of the physiological effects of intranasal administration, few studies have actually done so. In the present double-blind cross-over study we investigated the longevity of a single 24 IU dose of intranasal OT measured in saliva in 40 healthy adult males. Salivary OT concentrations were significantly higher in the OT condition, compared to placebo. This significant difference lasted until the end of testing, approximately 108 minutes after administration, and peaked at 30 minutes. Results showed significant individual differences in response to intranasal OT administration. To our knowledge this is the largest and first all-male within-subjects design study to demonstrate the impact of intranasal OT on salivary OT concentrations. The results are consistent with previous research in suggesting that salivary OT is a valid matrix for OT measurement. The results also suggest that the post-administration 'wait-time' prior to starting experimental tasks could be reduced to 30 minutes, from the 45 minutes typically used, thereby enabling testing during peak OT concentrations. Further research is needed to ascertain whether OT concentrations after intranasal administration follow similar patterns in females, and different age groups.
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Prior studies report that couples with higher relationship quality show higher oxytocin (OT) levels, yet other studies report those with higher distress have increased OT. This study investigated these competing predictions in the context of a support enhancement intervention among 34 young married couples (N = 68). Preintervention marital quality (Dyadic Adjustment Scale) was examined for associations with plasma and salivary OT levels 4 weeks apart and for changes between these time points within the intervention group. High relationship quality, not distress, was associated with higher OT in both saliva and plasma at both time points. No significant interaction was found between marital quality and intervention condition; relationship quality and support intervention were both independently associated with higher postintervention OT levels.
Article
Behavioral neuroscientists have shown that the neuropeptide oxytocin (OT) plays a key role in social attachment and affiliation in nonhuman mammals. Inspired by this initial research, many social scientists proceeded to examine the associations of OT with trust in humans over the past decade. To conduct this work, they have (a) examined the effects of exogenous OT increase caused by intranasal administration on trusting behavior, (b) correlated individual difference measures of OT plasma levels with measures of trust, and (c) searched for genetic polymorphisms of the OT receptor gene that might be associated with trust. We discuss the different methods used by OT behavioral researchers and review evidence that links OT to trust in humans. Unfortunately, the simplest promising finding associating intranasal OT with higher trust has not replicated well. Moreover, the plasma OT evidence is flawed by how OT is measured in peripheral bodily fluids. Finally, in recent large-sample studies, researchers failed to find consistent associations of specific OT-related genetic polymorphisms and trust. We conclude that the cumulative evidence does not provide robust convergent evidence that human trust is reliably associated with OT (or caused by it). We end with constructive ideas for improving the robustness and rigor of OT research.
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Intranasal oxytocin (OXT) application is emerging as a potential treatment for socio-emotional disorders associated with abnormalities in OXT system (re-) activity. The crucial identification of patients with such abnormalities could be streamlined by the assessment of basal and stimulus-induced OXT concentrations in saliva, using a simple, stress-free sampling procedure (i.e. an OXT challenge test). We therefore established the Regensburg Oxytocin Challenge (ROC) test to further validate salivary OXT concentrations as a practical, reliable and sensitive biomarker. OXT concentrations were quantified by radioimmunoassay in samples collected at home by healthy adult male and female volunteers before and after running ("Run") or sexual self-stimulation ("Sex"). In lactating women, salivary OXT concentrations were quantified before, during and after breastfeeding. Salivary OXT along with salivary cortisol and heart rate were monitored in healthy adult participants undergoing the Trier Social Stress Test (TSST). The home-based "Run" and "Sex" challenges as well as the laboratory-based TSST caused quantifiable, rapid, and consistent increases in salivary OXT (approximately 2.5-fold after 10-15min), which were similar for men and women. Breastfeeding did not result in measurably increased salivary OXT levels, probably because the short pulses of OXT release characteristic for lactation were missed. Taken together, ROC tests reliably assess the responsiveness of the OXT system (i.e., the increase in salivary OXT concentrations as compared to basal levels) to challenges such as "Run" and "Sex" at home or psychosocial stress (TSST) in the laboratory. Further studies with larger sample numbers are essentially needed in order to reveal individual differences in ROC test outcomes depending on, for example, genetic or environmental factors.
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Mother-infant bonding is a characteristic of virtually all mammals. The maternal neural system may have provided the scaffold upon which other types of social bonds in mammals have been built. For example, most mammals exhibit a polygamous mating system, but monogamy and pair bonding between mating partners occurs in ~5% of mammalian species. In mammals, it is plausible that the neural mechanisms that promote mother-infant bonding have been modified by natural selection to establish the capacity to develop a selective bond with a mate during the evolution of monogamous mating strategies. Here we compare the details of the neural mechanisms that promote mother-infant bonding in rats and other mammals with those that underpin pair bond formation in the monogamous prairie vole. Although details remain to be resolved, remarkable similarities and a few differences between the mechanisms underlying these two types of bond formation are revealed. For example, amygdala and nucleus accumbens-ventral pallidum (NA-VP) circuits are involved in both types of bond formation, and dopamine and oxytocin action within NA appears to promote the synaptic plasticity that allows either infant or mating partner stimuli to persistently activate NA-VP attraction circuits, leading to an enduring social attraction and bonding. Further, although the medial preoptic area is essential for maternal behavior, its role in pair bonding remains to be determined. Our review concludes by examining the broader implications of this comparative analysis, and evidence is provided that the maternal care system may have also provided the basic neural foundation for other types of strong social relationships, beyond pair bonding, in mammals, including humans. Copyright © 2015. Published by Elsevier Inc.