Are Men and Women Really That Different? Examining Some of Sexual Strategies Theory (SST)’s Key Assumptions about Sex-Distinct Mating Mechanisms

Abstract

Sexual Strategies Theory (SST; Buss and Schmitt 1993) suggests that, typically, men more so than women are more likely to spend proportionately more of their mating effort in
short-term mating, lower their standards in short-term compared to long-term mating, feel reproductively constrained, and
seek, but certainly not avoid, sex if pregnancy is likely in short-term relationships. A series of 4 survey studies each containing
hundreds of college student participants from the western portion of the United States were conducted to test these hypotheses.
The findings are inconsistent with SST but are consistent with Attachment Fertility Theory (AFT; Miller et al. 2005) that argues for relatively few evolved gender differences in mating strategies and preferences.

KeywordsEvolution–Sex-distinct mechanisms–Sexual Strategies Theory–Attachment Fertility Theory–Sex differences–Mating mechanisms–Mating strategies

Full text

Mating Mechanisms 1
Running Head: MATING MECHANISMS
Are Men and Women Really That Different?
!"#$%&%&'()*$+(*,()+"-#.()/0#/+'%+1(23+*04(5))2671(8+4(911-$:/%*&1(
about Sex-Distinct Mating Mechanisms
William C. Pedersen
California State University, Long Beach
Anila Putcha-Bhagavatula
California State University, Long Beach
Lynn Carol Miller
University of Southern California
William C. Pedersen
Department of Psychology
California State University, Long Beach
1250 Bellflower Blvd.
Long Beach, CA 90840-0901
phone: (562) 985-5010
fax: (562) 985-8004
e-mail: wpederse@csulb.edu

Mating Mechanisms 2
Abstract
Sexual Strategies Theory (SST; Buss & Schmitt, 1993) suggests that, typically, men more so
than women are more likely to spend proportionately more of their mating effort in short-term
mating, lower their standards in short-term compared to long-term mating, feel reproductively
constrained, and seek, but certainly not avoid, sex if pregnancy is likely in short-term
relationships. A series of 4 survey studies each containing hundreds of college student
participants from the western portion of the United States were conducted to test these
hypotheses. The findings are inconsistent with SST but are consistent with Attachment Fertility
Theory (AFT; Miller, Pedersen, & Putcha-Bhagavatula, 2005) that argues for relatively few
evolved gender differences in mating strategies and preferences.
Keywords: evolution; sex-distinct mechanisms; Sexual Strategies Theory; Attachment Fertility
Theory

Mating Mechanisms 3
Introduction
Mating is fundamental to evolutionary processes. Therefore, for an evolutionary
scientist, few domains offer as much explanatory promise.
S
exual
S
trategie s Theory
(SST; Buss
& Schmitt, 1993, Buss, 1994; Buss, 1995), a well-known evolutionary theory argues for evolved
sex-distinct mating mechanisms (e.g., preferences) for short-term and long-term mating due to
fundamental biologically-based sex differences in minimal levels of parental investment (e.g.,
physical limitations of pregnancy, labor, and nourishing young versus mere insemination). An
alternative view is expressed in Attachment Fertility Theory (AFT; e.g., Miller & Fishkin, 1997;
Miller et al., 2005) which argues that when the care of both parents increases the probability of
offspring survival, males and females are apt to evolve much more homologous or similar
mechanisms (Ziegler, 2000) impacting parental caregiving, pair-bonding, and mate selection
(Wynne-Edwards, 2001). This need for bi-parental care shifts the evolved pattern from sex-
distinct to sex-homologous mate selection mechanisms (Ziegler, 2000).
The overall purpose of the current paper is to test several hypotheses on which SST and
AFT make competing predictions. We accomplish this goal using four separate survey studies of
American college students designed to assess differences between men and women in a variety
of areas including the proportion of mating effort dedicated to short-term relationships (Study 1),
avoidance of pregnancy in short- and long-term relationships (Study 2), reproductive constraints
(operationalized as the difference between the number of different sexual partners ideally desired
relative to the number realistically expected) (Study 3), and standards for short- and long-term
partners (Study 4). The results are relevant to our understanding of the mating strategies and
preferences of both men and women and the possible evolutionary factors underlying such
behavior.

Mating Mechanisms 4
Below, we review some of the key theoretical assumptions crucial to SST and the
evidence that supports them. Over the course of four studies, we then ask a series of research
questions that directly test a number of these theoretical assumptions. In doing so, we contrast
the predictions of SST and AFT.
Overview of
S
exual
S
trategie s Theory
;-11(#&<()=3$%//(5>??@6(1/#0/(A%/3(/A*(#11-$:/%*&1B((23+4(#0'-+(/3#/(CD&(3-$#&(
evolutionary history, both men and women have pursued short-term and long-term matings
-&<+0(=+0/#%&(=*&<%/%*&1(A3+0+(/3+(0+:0*<-=/%E+(F+&+,%/1(3#E+(*-/A+%'3+<(/3+(=*1/1G (p. 205).
Then, they argue that Cdifferent adaptive problems must be solved when pursuing a short-term
sexual strategy as opposed to pursuing a long-/+0$(1+"-#.(1/0#/+'4G (p. 205). These first two
assumptions of the theory (precis points 1 and 2) do not yield any specific hypotheses or
predictions tested in Buss and Schmitt (1993).
Their next assumptions (precis :*%&/1(@H(IH(#&<(J6(4%+.<(:0+<%=/%*&1(0+'#0<%&'($+&71(
short-term (ST) mating strategies. Buss and Schmitt (1993) describe these sets of predictions as
central to SST. Let us proceed then, assumption by assumption, starting with the third precis
point.
Precis point 3: Differe nces between Men and Wo
m
en in Proportional Invest
m
ent in
S
T relative
to Total Mating Effort
Trivers' (1972) work provides the evolutionary theoretical framework for the work by
Buss and his colleagues (e.g., Buss, 1985; 1995; Buss & Schmitt, 1993) and others (e.g., Kenrick
& Keefe, 1992; Kenrick, Sadalla, Groth, & Trost, 1990). According to Trivers (1972), if women
(or men) invest
m
ore
in offspring, women (or men) should be more picky in choosing a mate.
Furthermore, if men (women) invest
less
in offspring, men (women) should compete more (i.e.,

Mating Mechanisms 5
devote a greater proportion of total mating effort to) for mates with whom they might
presumably minimally invest.
Buss and Schmitt (1993) argue that there are asymmetries in minimal levels of parental
investment %&(3-$#&1(1-=3(/3#/($+&(&++<&7/($%&%$#..4(%&E+1/(#1($-=3((e.g., sperm) as women
(e.g., fertilization, gestation, lactation) for offspring procreation and infant survival. If men are
.+11(%&E+1/%&'(/3#&(A*$+&H($+&71(1/#&<#0<1(%&(:%=K%&'(#($#/+(13*-.<(F+(.*A+0(/3#&(A*$+&71(#&<(
"men [
should
, italics added] devote a larger proportion of their total mating effort to short-term
mating than do women" (p. 205). This is precis Point 3 and it is a fundamental assumption of
SST. Still, in humans L unlike many other species -- both men and women may engage in both
short-term and long-term mating and both may invest a great deal in offspring. Note that SST
does
not
argue for general, non-overlapping, differences in behavioral strategy (i.e., men engage
in short-term mating while women pursue long-term mating; women invest heavily in offspring
while men do not). Rather, SST stresses that biological differences between men and women
(i.e., in minimal levels of investment) should predict differen=+1(%&($+&71(#&<(A*$+&71(
proportional invest
m
ent
in short-term mating relative to all other mating. We directly test this
assumption below.
Study 1
What if men did not "devote a larger
proportion
[italics added] of their total mating effort
to short-term mating than do women," (Buss & Schmitt, 1993, p. 205)? Then, the assumption
that minimal parental investment differentials impact gender differences in human mating would
be questionable. The theoretical link between such parental investment differentials, and
reproductive constraints on men and differential opportunities in short-term relationships would
be severed.

Mating Mechanisms 6
Buss and Schmitt (1993), however, did not directly test this assumption. Their prediction
1 is the prediction most directly relevant, but it is operationalized by examining the extent to
which men versus women "are currently seeking a short-term mate" (p. 210). The
proportion
of
short-term mating to total mating effort is not assessed. Therefore, Buss and Schmitt (1993)
cannot address whether seeking a short-term mate is a "larger component of men's sexual
strategy than of women's sexual strategy" (Hypothesis 1, p. 210). Nor can they address whether
"men devote a larger proportion of their total mating effort to short-term mating than do women"
(precis point 3, p. 205). An alternative is clear: men and women may each devote the same
amount of effort to short-term mating relative to their respective total mating effort.
Subsequently, Schmitt, Shackelford, Duntley, Tooke, and Buss (2001) attempted to look
at proportions by asking college participants to indicate on a 7-point scale the degree to which
they are seeking both a short-term and long-term mating partner with a value of 1 indicating
C=-00+&/.4(&*/(#/(#..(1++K%&'G(#&<(#(E#.-+(*f 7 =*00+1:*&<%&'(/*(C=-00+&/.4(1/0*&'.4(1++K%&'.G((9(
ratio was then formed using these two relationship types with findings supporting SST. There
are two problems with this approach. First, Schmitt et al. (2001) only looked at short-term and
long-term mate seeking. They did not ask about intermediate duration relationships (e.g., dating,
going steady, intermediate-length affairs, etc.). Buss and Schmitt (1993) themselves
acknowledge that in addition to short-term and long-term relationships, humans also engage in
intermediate-term relationships. Intermediate relationships are, in fact, quite common among
college students L the typical population sampled in this research. For example, in the data set
employed in Study 1 we asked college participants if they have ever had a short-, intermediate,
and long-term sexual relationship. Whereas 35.9% and 15.5% of participants indicated that they
had a short- and long-term sexual relationship, respectively, a full 62.9% said they had an

Mating Mechanisms 7
intermediate-term sexual relationship. Second, conceptually and statistically Schmitt et al.
(2001) are interested in proportions. But, their measures do not allow them to look at proportions
because their measures do not conform to the requirements of ratio scales. A ratio scale of
measurement is one in which differences between scale values can be quantified and there exists
an absolute zero point (Colman, 2001). For example, time and money are both ratio scales.
There is an absolute zero (no money, no time) and participants can count up the amount of time
or money devoted to an activity; each amount of money or time has absolute value relative to
other amounts of money or time that enables division. That is, 50 dollars is half of 100 dollars;
40 minutes is twice as long as 20 minutesH(+/=B((M-0/3+0$*0+H(C23+(+"%1/+&=+(*,(#&(#F1*.-/+H(
nonarbitrary zero point means that we can measure the absolute amount of the variable; that is,
we can measure the distance from zero. This makes it possible to compare measurements in
terms of r#/%*1BG(5N0#E+//+0(O(P#..&#-H(QRRSH(:B(Q>6B(23+0+,*0+H(/*(*-0(K&*A.+<'+H(;-11(#&<(
)=3$%//71(5>??@6(=0%/%=#.(#11-$:/%*&(3#1(&*/(F++&(#<+T-#/+.4(/+1/+<B((
We addressed this assumption, and the inadequacies of prior attempts to assess it, in
examining our first research question L Is there a difference between men and women in the
proportion of mating effort devoted to short-term to all dating relationships? We operationalize
C$#/%&'(+,,*0/G(F*/3(%&(/+0$1(*,(5#6(/%$+(#&<(5F6($*&+4(1:+&/(:-01-%&'(#(0+.#/%*&13%p because
these are both valuable resources (requiring effort) that are expended in the context of dating
relationships and they are measured on a ratio scale. Furthermore, to assess the full range of
dating relationships we collected data on short-, intermediate-, and long-term relationships.
As discussed above, SST would clearly hypothesize that men should spend
proportionately more of their mating effort in short-term relationships compared to women.
AFT, in contrast, argues for predominately homologous (sex-similar, not sex-distinct) patterns of

Mating Mechanisms 8
mating mechanisms in humans. As such, AFT would not predict differences between men and
women in mating effort, neither in the proportion of time (Hypothesis 1) nor proportion of
money (Hypothesis 2) spent in pursuit of short-term mating relationships.
Method
Participants
. Three hundred forty six undergraduate students (89 males and 257 females)
from the University of Southern California with a mean age of 19.89 years (
S
D
= 3.52, range 17-
57) participated for course credit. College students were the sample of interest here because
college students were the sample of interest in the vast majority of empirical studies we
reviewed. Furthermore, mating goals are presumably active for this group. The current sample
was 42.9% Caucasian, 23.4% Asian, 15.0% Hispanic, and 7.9% African American. In addition,
SBIU(*,(/3+(:#0/%=%:#&/1(0+1:*&<+<(/*(/3+(+/3&%=%/4(T-+1/%*&(F4(%&<%=#/%&'(CV/3+0G(#&<(QBJU(<%<(
not respond at all.
Measures and Procedure.
A survey was administered in multiple sections of an
Introductory Psychology. We tested our hypotheses with two separate dependent variables. For
the first we asked participants in an
open-ended for
m
at
to use numbers to indicate the average
amount of
ti
m
e
and
m
oney
they devote in a typical week in pursuing short-term, intermediate,
and long-term relationships (e.g., 2 hours, $30, etc.). Relationships were defined as specified by
Buss and Schmitt (1993): Short-term relationships were defined as brief affairs or one night
stands, intermediate relationships were defined as dating or "going steady," and long-term
relationships were defined as potential marriage partners. These two questions produced
responses that are measured on a ratio scale.
To assess whether a gender difference exists in the proportion of mating effort devoted to
short-term dating relationships, we divided responses on the short-term items by the total

Mating Mechanisms 9
responses to all three relationship types. For example, imagine a participant who indicated that
she spends $15, $20, and $10 per week pursuing short-, intermediate-, and long-term
relationships, respectively. This individual therefore spends a total of $45. The proportion of
her total monetary outlay devoted to short-term relationships would be .33 (i.e., $15 / $45 = .33 L
that is, 33%).
The second dependent variable was produced by asking participants to separately answer
the same two questions using a
s cale for
m
at
. Specifically, responses for the time devoted to
seeking each relationship type were on a 6-point scale, with each value labeled, ranging from "no
time at all" to "eight or more hours a week." The questions concerning the amount of money
spent each week pursuing each type of relationship were on a 7-point scale, with each value
labeled ranging from "no money at all" to "over $100".
Results and Discussion
On the open-ended questions that produce a ratio scale, 27.4% of participants reported
spending no
ti
m
e
and 52.8% indicated that they spend no
m
oney
pursuing any type of
relationship. We considered only those spending time or money in pursuit of any type of
relationship. Among those who are spending time pursuing any type of relationship, Men (
M
=
.30,
S
D
= 0.34) do not differ from women (
M
= .24,
S
D
= 0.32) in the proportion of
ti
m
e
spent
seeking a short-term mate,
F
(1,237) = 1.44,
p
>.10 (Hypothesis 1). In a similar fashion, for those
who are spending
m
oney
pursuing some type of relationship, Men (
M
= .25,
S
D
= 0.33) do not
differ from women (
M
= .17,
S
D
= 0.29) in the proportion of money spent seeking a short-term
mate,
F
(1,149) = 1.96,
p
>.10 (Hypothesis 2; see Table 1).
Although we recognize the statistical problem of using ratios here, to compare our
findings with the earlier findings by Schmitt et al. (2001) that used a fixed scale, we then

Mating Mechanisms 10
replicated these findings using the 1-6 and 1-7 point ratio-like scales for time and money,
respectively. Specifically, for both proportion of
ti
m
e
(
M
= .32,
S
D
= 0.15 men;
M
= .30,
S
D
=
0.14 women;
F
(1,334) = 2.50,
p
>.1) and
m
oney
(
M
= .31,
S
D
= 0.10 men;
M
= .30,
S
D
= 0.08
women;
F
(1, 337) = 0.67,
p
>.1) spent in a short-term versus other relationships, there were no
significant differences between men and women (see Table 1). We also employed a multivariate
analysis of variance (MANOVA) to analyze the data, since loss of cases in doing so was not an
issue (as it was for the other time and measure variables). Consistent with the univariate results,
the MANOVA revealed a lack of an overall difference for men versus women,
F
(2,333) = 1.34,
p
>.1.
Additional analyses revealed a difference in age with men (
M
= 20.83,
S
D
= 5.68) being
older than women (
M
= 19.56,
S
D
= 2.30),
F
(1,342) = 8.64,
p
<.01). Although age was not
correlated with any of the dependent measures (all
p
-values>.10) we nonetheless re-ran all the
analyses above using age as a covariate. Age was not a significant covariate in any of the
analyses (all
p
-values>.10) and the results replicated our previous findings of no significant
differences between men and women.
Our findings do not show evidence for a gender difference in the proportionate amount of
effort devoted to short-term mating (as is predicted by Sexual Strategies Theory). Therefore, the
third p0+=%1(:*%&/(*,(;-11(#&<()=3$%//71(5>??@6(/3+*04(was not supported. Our findings did not
support the claim /3#/(CF+=#-1+(*,(#(,-&<#$+&/#.(#14$$+/04(F+/A++&(/3+(1+"+1(%&($%&%$-$(
levels of parental investment, men devote a larger proportion of their total mating effort to short-
/+0$($#/%&'(/3#&(<*(A*$+&G(5:B(QRJ6B As expected however, these findings are consistent with
Attachment Fertility Theory (e.g., Miller & Fishkin, 1997; Miller et al., 2005) that would not

Mating Mechanisms 11
expect differences between men and women in the proportion of total mating effort devoted to
short-term dating relationships.
Study 2
Study 1 investigated differences between men and women in the proportion of both time
and money spent pursuing short-term relationships. We now turn to an examination of sexual
opportunities and constraints. The fourth precis point of Buss and Schmitt (1993) argues that
"the adaptive problems that women must solve when pursuing each strategy are different from
those that men must solve, although some problems are common to both sexes" (p. 206).
Although there are no specific hypotheses and predictions associated with this precis point, it is
%$:*0/#&/(,*0(:0+=%1(:*%&/(JB((23+0+,*0+H(.+/71(/#K+(#(=.*1+0(.**K(#/(%/B
Buss and Schmitt argue for sex-differentiated adaptive problems "because the
reproductive opportunities and reproductive constraints differ for men and women in these two
contexts" (p. 205). 23#/(%1H(/3+0+(%1(#&(#&/+=+<+&/H(C0+:0*<-=/%E+(*::*0/-&%/%+1G(#&<(#(=*&1+T-+&/(
(e.g., men, more so than women, desire more partners).
According to Buss and Schmitt (1993), the chief benefit from short-term mating is an
increase in the number of offspring produced: "historically, men appear to have achieved
increases in reproductive success primarily through increases in the number of sexual partners,
not through increases in the number of offspring per partner (Betzig, 1986; Dawkins, 1986)" (p.
207). But, what does number of partners mean here (Betzig, 1986)? For clarity, primatologists
(Dixson, 1998) differentiate monogamous and polygynous mating systems (e.g., long-term) from
other systems involving more promiscuous mating systems (e.g., short-term) across primates.
When men have multiple wives in polygynous matings (e.g., Betzig, 1986), they are in relatively
long-ter
m
relationships
, and not short-term ones. It is, therefore, not at all clear what role short-

Mating Mechanisms 12
/+0$($#/%&'1(3#E+(3%1/*0%=#..4(:.#4+<(%&(%&=0+#1%&'($+&71(0+:0*<-=/%E+(1-==+11(F+4*&<(/3#/(
achieved through more long-term, monogamous or polygynous, mating. Nevertheless, let us
suppose, for the moment, that men -- more so than women -- do increase their reproductive
opportunities with short-term matings. What then?
Buss and Schmitt (1993) argue, in their precis point 4, that because of these greater
reproductive opportunities in short-term mating for men, men are more likely than women to
solve a specific set of problems (e.g., seek more short-term relationships). There are a number of
questions here. Regarding the first part of the clause of precis p*%&/(IH(C;+=#-1+(/3+(0+:0*<-=/%E+(
opportunities and reproductive constraint1(<%,,+0(,*0($+&(#&<(A*$+&HG(A+(=#&(#1KH(C90+(/3+(
0+:0*<-=/%E+(*::*0/-&%/%+1(,*0($+&(#&<(A*$+&(<%,,+0+&/WG(#&<(C90+(/3+(0+:0*<-=/%E+(=*&1/0#%&/1(
<%,,+0+&/(,*0($+&(#&<(A*$+&WG((X+'#0<%&'(/3+(1+=*&<(:#0/(*,(/3+(=.#-1+(*,(precis point 4, if the
assumptions of the first part of the clause are found to be unsupported, then the second part of
/3+(=.#-1+H(C/3+(#<#:/%E+(:0*F.+$1(/3#/(A*$+&($-1/(1*.E+(A3+&(:-01-%&'(+#=3(1/0#/+'4(#0+(
<%,,+0+&/(,0*$(/3*1+(/3#/($+&($-1/(1*.E+HG(%1(&+=+11#0%.4(#.1*(&*/(1-::*0/+<B
Reproductive opportunities in short-ter
m
m
ating
Now, let's consider the first clause of this precis point again. One might argue that, given
Sexual Strategies Theory, men, compared to women, would particularly desire offspring in short-
term relationships. After all, Buss and Schmitt (1993) argue that this is where the reproductive
opportunities are greater for men; the costs are lower for men than for women and this is how,
according to Buss and Schmitt (1993), men primarily enhance their reproductive success. Given
the relative benefits and costs, wouldn't Sexual Strategies Theory predict that men would find it
desirable to have offspring from such a coupling? Certainly, Sexual Strategies Theory seems
inconsistent with the possibility that men would
avoid sex
in short-term relationships, compared

Mating Mechanisms 13
to long-term relationships. This should, if anything, be more true if pregnancy seemed likely.
The pattern for women, in contrast, is less clear. But, because women would have the additional
F+&+,%/(*,($+&71(1-::*rt in long-term but not in short-term relationships, short-term matings
resulting in pregnancy should generally be less favored.
It should be noted that the strategy -- having short-term relationships in order to have
more offspring -- would not need to be a conscious one. Rather, men who wanted more short-
term relationships might not consciously seek more offspring.
This seems consistent with an
argument Buss and Schmitt (1993) make with their eleventh precis point that "Strategies are
defined as evolved solutions to adaptive problems, with no consciousness or awareness on the
part of the strategist implied."(p. 206). Nevertheless, if men knew or suspected that pregnancy
was likely L consciously or not L SST would certainly not argue that this would deter them from
wanting a short-term relationship. In fact, if anything, one might expect that SST would argue
that men would be more likely to seek such a mating (e.g., if they suspected consciously or not
that pregnancy was likely), thereby enhancing their reproductive success. Based on this
reasoning, Sexual Strategies Theory would suggest that, given the relative benefits and costs,
men would
not
be particularly likely to avoid having sex, and certainly would not be more likely
to avoid short-term mating than long-term mating if pregnancy was likely. Study 2 is designed
to formally test this hypothesized difference.
Attachment Fertility Theory would make an entirely different prediction. AFT argues
that bi-parental care was biologically, chemically, and psychologically adapted for in human
evolution. Specifically, without bi-parental care almost half of the children among hunter-
gatherers do not survive childhood (for a review, see Geary, 2000) and historically childhood
mortality without fathers may have been even higher (Hrdy, 1999). By definition, fathers are

Mating Mechanisms 14
more likely to participate in care giving in the context of long-term relationships. This in turn
increases the likelihood of offspring survival. AFT would therefore predict that men would
avoid having sex in a short-term (relative to a long-term) relationship if pregnancy were likely to
occur. What would AFT predict for women? Among mammals, when fathers matter for
offspring survival, evolved homologous (gender-similar) mechanisms prevail (Wynne-Edwards,
2001; Ziegler, 2000). As such, AFT would predict that women would show the same pattern as
men (i.e., more avoidance of sex in short-term relationships if sexual relations would likely result
in pregnancy). Study 2 directly tested the competing predictions of SST and AFT by asking both
men and women about reproductive opportunities. We operationalize this concept by asking
individuals the extent to which they would avoid sex in the context of both short- and long-term
relationships if pregnancy was a likely outcome. Our hypothesis was that both men and women
would show the same pattern of more strongly avoiding pregnancy in a short-term relative to a
long-term relationship.
Method
Participants.
Two hundred seventeen undergraduate students (66 males and 151
females) from the University of Southern California with a mean age of 19.38 years (
S
D
= 1.84,
range 17-28) participated for course credit. The sample was 43.6% Caucasian, 18.8% Asian,
13.3% Hispanic, and 5.0% African American. In addition, 16.5% of the participants responded
/*(/3+(+/3&%=%/4(T-+1/%*&(F4(%&<%=#/%&'(CV/3+0G(#&<(QBSU(<%<(&*/(0+1:*&<(#/(#..B((
Measures and Procedure.
A survey was administered in multiple sections of an
Introductory Psychology. For short-term and long-term relationships, participants separately
rated on a 7-point Likert scale the extent to which they would either very actively seek (+3) or
very actively avoid (-3) having sex if they knew that there was a high probability that having sex

Mating Mechanisms 15
on that particular night would result in pregnancy. A value of 0 was marked "neither actively
seek or avoid".
Results and Discussion
The age of men (
M
= 19.52,
S
D
= 1.84) and women (
M
= 19.32,
S
D
= 1.84) did not
differ,
F
(1,215) = 0.53,
p
>.10). Furthermore, age was not correlated with any of the dependent
measures (all
p
-values>.10). As such, age was not used as a covariate in the analyses below.
Men were more likely to avoid sex if pregnancy was likely in a short-term relationship
(
M
= -2.03,
S
D
= 1.76) than in a long-term relationship (
M
= -0.58,
S
D
= 2.05),
t
(63) = 6.11,
p
<.001 (see Table 2). Sexual Strategies Theory argues that the benefit to cost ratio in achieving
a pregnancy for men is especially great in short-term compared to long-term mating. Therefore,
this finding is not consistent with SST but it is consistent with the prediction of AFT. The
pattern for women was similar to the pattern for men (
M
= -2.29,
S
D
= 1.76 for short-term
relationships;
M
= -1.04,
S
D
= 2.07 for long-term relationships,
t
(148) = 8.28,
p
<.001; see Table
2).
To further explore the role of gender and relationship length on decisions about whether
to have sex if pregnancy is likely, a 2 (gender) x 2(relationship type) mixed ANOVA was
performed. There was a main effect for relationship type,
F
(1,211) = 95.48,
p
<.001, indicating
that both men and women were significantly more likely to avoid pregnancy in a short-term
compared to a long-term relationship. However, neither the main effect of gender nor the
interaction of relationship type and gender were statistically significant (both p-values>.15).
Therefore, it was not the case that men were more likely than women to desire sex in a short-
term relationship if pregnancy was likely. Furthermore, men were more likely to desire sex if
pregnancy was likely in a long-term than in a short-term relationship. These combined findings

Mating Mechanisms 16
too seem incongruent with a major assumption in the underpinning logic of Sexual Strategies
Theory but match our predictions based on Attachment Fertility Theory.
Study 3
In Study 3 we continue to investigate whether men and women experience sexual
constraints. D&(;-11(#&<()=3$%//71(5>??@6(,*-0/3(:0+=%1(:*%&/H(/3+4(#0'-+(/3#/(/3+(=*&1/0#%&/1(#1(
well as the opportunities differ for men and women in short-term and long-term relationships.
precis point 5 argues that "men historically have been constrained in their reproductive success
primarily by the number of fertile women they can inseminate" (Buss & Schmitt, 1993, p. 206).
Thus, men -- according to this perspective -- want many partners, but may fall short because they
are constrained by women. Do men feel so constrained? If this were true, we7<(+":+=/(that
$+&71(
ideally desired
number of partners (e.g., no reproductive constraints), within a given
period o,(/%$+H(A*-.<(F+('0+#/+0(/3#&($+&71(+":+=/+<(
real
number of partners (i.e., number of
partners expected given that these reproductive constraints exist). On the other hand, if men do
&*/(,++.(1*(C=*&1/0#%&+<HG(A+($%'3/(+":+=/(/3#/H(*&(#E+0#'+H(/3+4(A*-.<(not differ in the number
of partners they realistically and ideally expect to have.
From the vantage point of Sexual Strategies Theory, the case for women seems less clear.
For women, "the reproductive benefits of short-term mating as an end in itself are less direct and
the potential costs more steep" (Buss & Schmitt, 1993, p. 221). Viewing a short-term
relationship as an entrée into a more long-term relationship (Buss & Schmitt, 1993), however,
might justify the costs. Nevertheless, women may realistically expect that this strategy may
sometimes not result in a long-term relationship and that thereby they may end up with more
partners than they might ideally desire. This not only represents time wasted looking for a long-
term partner but might also lead to reputation loss (making a longer term relationship less likely).

Mating Mechanisms 17
In addition, women using this strategy run the risk of investing in partners who are low in
commitment and/or resources, both of which are not advantageous from an evolutionary
perspective. Thus, although a hunter-gatherer woman might have many offspring with different
men, those offspring might not themselves survive to child-bearing age (Shostak, 1981). Finally,
#./3*-'3(C:0*$%1=-*-1G($#/%&'($#4(F+(1%$:.4(#(&#/-0#.(1/+:(/*A#0<1(.*&'-term mating (Miller
et al., 2005), men who show a greater interest in and orientation towards short-term mating in
general may be more likely to also demonstrate narcissism and psychopathy (Jonason, Li,
Webster, & Schmitt, 2009), qualities that certainly do not facilitate long-term pair-bonds.
In Study 3 we test the idea of sexual constraints by asking men and women both the ideal
number of different sexual partners they desire and the number of partners they realistically
expect to have. The prediction of Sexual Strategies Theory seems clear L the number of sexual
partners desired by men will exceed the number they realistically expect (viz. they are sexually
constrained). From the perspective of SST, the situation for women is somewhat less apparent.
Furthermore, it seems reasonable that SST would predict a gender difference in constraint with
men perceiving themselves as more constrained than women.
As discussed above, Attachment Fertility Theory argues that bi-parental care was adapted
for in human evolution. In contrast to SST, AFT hypothesizes that fathers played a greater role
in caring for their offspring and devoted fewer resources to obtaining numerous short-term
partners. As such, AFT would predict that while we might expect variability within women or
variability within men in feeling more or less constrained in achieving the number of partners
desired, neither men nor women should, on the average, feel particularly constrained. We
directly test these competing hypotheses of SST and AFT below.
Method

Mating Mechanisms 18
Participants.
Two hundred seventy two undergraduate students from the University of
Southern California participated for course credit. Of these 109 were males and 163 were
females. The average age of participants was 19.37 years (
S
D
= 2.08, range 17-36). The sample
was 39.3% Caucasian, 30.5% Asian, 16.5% Hispanic, and 7.7% African American. In addition,
JBJU(*,(/3+(:#0/%=%:#&/1(0+1:*&<+<(/*(/3+(+/3&%=%/4(T-+1/%*&(F4(%&<%=#/%&'(CV/3+0G(#&<(RBIU(<%<(
not respond at all.
Measures and Procedure.
A survey was administered in multiple sections of an
Introductory Psychology. As in a study reported in Buss and Schmitt (1993), participants were
first asked to estimate how many sexual partners they would
ideally
like to have over a series of
time intervals: during the next month, 6 months, 1 year, 2 years, 3 years, 4 years, 5 years, 10
years, 20 years, 30 years, and a lifetime. In addition, participants were also asked to estimate
how many sexual partners they thought they could
realistically
have over the same time
intervals, a series of questions Buss and Schmitt (1993) did not ask. Constraint was computed as
the difference between partners desired and partners expected for each time period. High
positive numbers reflected constraint with ideal scores greater than expected scores.
Results and Discussion
The distributions of constraint for men and women were significantly skewed. For the
thirty year period, for example, skew was quite high for both men (
Z
= 9.79,
p
< .0000000001)
and women (
Z
= 14.31,
p
< .0000000001). In such cases medians are a better measure of central
tendency than are means (Wilcox, 1997). The median response for the thirty year period for both
$+&(#&<(A*$+&(A#1(C&*(<%,,+0+&=+G(F+/A++&(/3+(&-$F+0(*,(:#0/&+01(%<+#..4(<+1ired and
realistically expected (
MJ
= 0, p = 1.00, 95% confidence interval of -0.0017, 0.0017) (see Figure
1). Consistent with this finding, the median value was also zero for both men and women for the

Mating Mechanisms 19
other ten time periods as well. In addition, the average age of men (
M
= 19.66,
S
D
= 2.33) and
women (
M
= 19.19,
S
D
= 1.89) did not significantly differ so age was not employed as a
covariate.
Consistent with our hypothesis and the expectations of Attachment Fertility Theory, these
findings suggest that both men and women, typically, are not constrained in achieving the
number of partners they desire. These findings, however, do not support Sexual Strategies
Theory. Specifically, if men are not "constrained in their reproductive success primarily by the
number of fertile women they can inseminate" (Buss & Schmitt, 1993, p. 206), can there be
evolutionary-based gender differences in the problems that follow from this non-constraint?
Obviously not.
Precis point 5 specifies four problems that according to Buss and Schmitt (1993) men had
to overcome
becaus e they were " constrained
.
"
Despite lack of support for the assumption of
C=*&1/0#%&/G(found in Study 3, we nevertheless want to consider the first set of these predictions
from Buss and Schmitt (1993) which involve the first of these problems, the "problem of
number" (p. 210).
Distinct patterns of nu
m
bers of short-ter
m
partners desired for
m
e n versus for wo
m
en?
"Men may have evolved over human evolutionary history a powerful desire for sexual
access to a large number of women (cf. Symons, 1979)" (p. 208). This leads them to their
prediction 2, which is, "for any given period of time (e.g., a month, a year, a decade, or a
lifetime), men will desire a larger number of mates than will women (solution to the problem of
number)" (Buss & Schmitt, 1993, p. 210). Do most men ideally desire a large number of mates?
Buss and Schmitt (1993) found statistically significant differences between the means for
men and the means for women at all 11 time intervals from a month to a lifetime. In fact, we

Mating Mechanisms 20
replicated this effect (Miller & Fishkin, 1997; Pedersen, Miller, Putcha, & Yang, 2002). As
strong as these findings may appear, Buss and Schmitt's (1993) inferences rely heavily on t-test
comparisons of means. We have argued that this matters both conceptually and statistically
(Pedersen et al., 2002). First, these data are heavily skewed. For example, even in Buss and
Schmitt's (1993) original data which they provided to us, for the "next 30 years" time frame, the
skew for men was highly significant (
Z
= 8.94,
p
<.000001). Given that these data violate the
assumptions of parametric tests, medians rather than means are a more appropriate measure of
central tendency (Wilcox, 1997). As we have reported elsewhere (Pedersen et al., 2002),
although we readily replicate Buss and Schmitt's findings for mean differences between men and
women in number of partners desired per time frame, the story is different when we look at
medians.
We (Pedersen et al., 2002) find at the thirty-year time frame, for example, that over 50%
of both men and women desire no more than 1 sexual partner. Across time frames there are few
gender differences in these median values. Our sample medians, especially for men, differ
however, from those reported by Buss and his colleagues (Buss, 2000; Greiling & Buss, 2000).
For example, calculated median values for the thirty year time frame using the Buss and Schmitt
(1993) data set are 8 for men and 3 for women whereas our values were 1 and 1. More recent
cross-cultural work by proponents of SST (see Schmitt, 2003) indicates that medians for men
and women (except for men in Oceania -- i.e., Australia, Fiji & Pacific Islands, and New
Zealand) were also 1. Although medians were not explicitly presented in Schmitt (2003),
information about the medians can be deduced from Figure 2 in that article. Although there may
be differences in the distributions for men and women, and differences among men and among
women are interesting ones to examine (see Miller and Fishkin, 1997), the medians (that would

Mating Mechanisms 21
seem critical to SST) do not appear to differ. The logic of Sexual Strategies Theory, so tied to
non-overlapping biological propensities (e.g., sperm production; bearing offspring), seems
consistent with the expectation that at the very least,
m
ost
men would differ from
m
ost
women in
their sexual strategies. Medians therefore, could provide a particularly useful measure of central
tendency with which to examine a hypothesis about evolved, biologically-based, differences
between men and women.
But this type of data cannot address the question of whether the relationships desired are
actually short-term ones, intermediate term ones, or more long-term relationships. Additional
research (Pedersen et al., 2002) provides convergent findings. In that work, we more directly
#<<0+11+<($+&(#&<(A*$+&71(<+1%0+(,*0(13*0/-term and long-term mates, and the dating trajectory
that would be considered ideal by men and women. First, virtually all men (98.9%) and virtually
all women (99.2%) desire to eventually settle down in a long-term mutually exclusive sexual
relationship. Second, of those who have not yet found such a partner, the median desired time
frame for ideally dating before finding this person is five years into the future. Third, when
asked how many short-term and long-term partners men and women ideally desired, we
replicated both a mean difference, and no median difference between men and women. Fourth,
both men and women desired a median number of 0 short-term partners. Additional partners
sought before the long-term partner, were intermediate dating partners -- not short-term dating
partners.
Taken together, these findings are consistent with the possibility that for most of our
lives, after an initial promiscuous seeking and dating phase in the teens and 20's in the U.S., men
and women would ideally prefer to focus on a long-term relationship that typically lasts for
decades (Laumann, Gagnon, Michael, & Michaels, 1994). These data, as well as our own from

Mating Mechanisms 22
various studies reported here (see also Miller & Fishkin, 1997), suggest that most men and
women eventually seek relatively enduring pair-bonds (e.g., from sometime in their 20's
forward). This time period is consistent with that found in national representative samples
regarding the time prior to marriage or first cohabitation (Laumann et. al., 1994). If children are
desired, it seems likely that, in general, they would tend to be desired in the context of such a
more enduring emotionally close pair-bond. This suggestion seems consistent with our finding,
reported earlier, that both men and women would be more likely (less unlikely) to have sex in a
long than short-term relationship, if pregnancy was likely.
In summary, Study 3 showed no evidence that men are constrained in their search for
sexual partners. In addition, our previous work discussed above indicates that it is not the case
that most men and women differ in their desired number of partners. Furthermore, to the extent
that individuals want additional partners before settling down with a long-term partner, these
desired partners were in the context of intermediate-term (not short-term) dating relationships.
Study 4
Study 4 is designed to test an additional research hypothesis proposed by Sexual
Strategies Theory. Specifically, do men, more so than women, lower their "standards" in short-
term compared to long-term contexts? ;-11(#&<()=3$%//71(5>??@6(Y0+<%=/%*&(I(%1(/3#/H(Z9=0*11(
all desired attributes in potential short-term mates, men will impose less stringent standards than
women impose." Part of the argument here is that men evolved an adaptive strategy involving a
"relaxation of standards imposed for acceptable short-term partners. Elevated standards, by
definition, preclude a large number of women from exceeding them. The relaxation of standards
should apply to a wide range of mate characteristics" (p. 208). By lowering their standards in
short-term contexts, men thereby could, according to this argument, solve the "problem of

Mating Mechanisms 23
number" (e.g., finding numerous short-term partners). Understanding whether men "relaxed"
their standards in short-term relationships more so than women requires a comparison with what
men do when they do not have to solve the "number" problem: what men do in long-term
contexts. Buss and Schmitt (1993) do not give us the comparison with long-term contexts for
men and women against which to gauge if "standards" have, in fact, been "relaxed" for one
gender more so than for the other.
Sexual Strategies Theory, in essence, predicts an interaction. There should be more of a
difference between short-term and long-term contexts for men than for women on attributes of
the same polarity (positive or negatively valued). But, that comparison is not examined by Buss
and Schmitt (1993). We directly test this hypothesis in Study 4. Furthermore, although SST
would predict an interaction such that relationship context differentially affects preferences for
men and women, consistent with Attachment Fertility Theory we predict similar patterns for both
men and women (viz. the absence of an interaction) for both positive (Hypothesis 1) and
negative (Hypotheses 2) valenced partner traits.
Method
Participants.
An undergraduate college sample of 342 women and 243 men from the
University of Southern California participated in the study for course credit. The average age of
participants was 19.28 years (
S
D
= 2.23, range 17-43). The sample was 43.5% Caucasian,
28.1% Asian, 15.9% Hispanic, and 7.5% African American. In addition, 5.0% of the participants
0+1:*&<+<(/*(/3+(+/3&%=%/4(T-+1/%*&(F4(%&<%=#/%&'(CV/3+0GB((
Measures and Procedure.
A survey was administered in multiple sections of an
Introductory Psychology. Participants rated a number of preferences provided to us by David
Buss including 24 positive characteristics that were of the same polarity for short-term and long-

Mating Mechanisms 24
term contexts for men and women and 13 negative preferences using a 7-point Likert scale from
-3 (highly undesirable) to +3 (highly desirable). These items were designed to cover a broad
range of human characteristics so as to assess for gender differences in standards for a romantic
partner. The
positive
items included: good financial prospects, physically attractive, kind and
understanding, sexually loyal, creative and artistic, exciting personality, likely to earn a lot of
money, college graduate, good heredity, easygoing, likely to succeed professionally, intelligent,
reliable future career, gives me gifts early on, good looking, sex appeal, healthy, good
housekeeper, emotionally close, emotionally warm, honest, ambitious, able to protect me from
physical harm, and athletic. The
negative
items included: prudish, financially unsupportive, low
sex drive, unfaithful, promiscuous, sleeps around a lot, lacks ambition, uneducated, financially
poor, stingy, emotionally cold, unemotional, and emotionally distant. To parallel the analyses of
Buss and Schmitt (1993), we formed a composite of the 24 positive items 5[0*&F#=371(#.:3#1(\(
.86 and .84 for short- and long-term, respectively) and a separate composite of the 13 negative
items 5[0*&F#=371(#.:3#1(\(B]?(#&<(B^?(,*0(13*0/- and long-term, respectively) to look at overall
C.*A+0%&'G(*,(1/#&<#0<1B((Specifically, averages were computed using the relevant items so that
the resulting scores would reflect the original 7-point Likert scale discussed above.
Results and Discussion
For the
positive
items, in both short-term
and
long-term contexts, overall, there was a
main effect such that men (
M
= 1.14,
S
D
= 0.63 short-term;
M
=1.61,
S
D
= 0.51 long-term) had
less extremely positive ratings than women (
M
= 1.41,
S
D
= 0.68 short-term,
M
=1.87,
S
D
= 0.57
long-term;
F
(1,574) = 36.10,
p
<.001) (see Table 3). There was also a context main effect such
that evaluations for both men and women were more positive in long-term than short-term
contexts,
F
(1,574) = 326.85,
p
<.001. This latter finding suggests that both men and women

Mating Mechanisms 25
appear to "lower their standards" in short-term compared to long-term contexts. But, do men
lower them more than women? No, there was not a significant interaction here,
F
(1,574) = 0.06,
p
>.10.
We also examined negatively valued items in short-term and long-term contexts. Were
these less negatively evaluated in short-term than in long-term contexts? And was this "lowering
of standards" greater for men than for women? Men generally were less negative in both short-
term and long-term contexts regarding negatively valued characteristics (
M
= -1.53,
S
D
= 0.79
short-term;
M
= -2.03,
S
D
= 0.56 long-term) than were women (
M
=-1.91,
S
D
= 0.71 short-term;
M
=-2.35,
S
D
= 0.52 long-term;
F
(1,573) = 55.44,
p
<.001) (see Table 3). And, these evaluations
are more negative (pickier in long-term than in short-term relationships) following the logic of
Buss and Schmitt (1993),
F
(1,573) = 266.94,
p
<.001. But, do men drop their standards more than
women? No, even with a large sample size, there is not a significant interaction,
F
(1,573) =
1.26,
p
>.10.
We also employed a mixed multivariate analysis of variance (MANOVA) to analyze the
overall effects across both short- and long-term relationship contexts. Consistent with the
univariate results, the mixed MANOVA revealed a lack of an overall interaction: That is, both
men and women showed the same pattern of differences across context ,
F
(2,572) = 0.69,
p
>.1.
Additional analyses revealed a difference between men (
M
= 19.58,
S
D
= 2.30) and
women (
M
= 19.07,
S
D
= 2.16) in age, with men being significantly older than women,
F
(1,579)
= 7.40,
p
<.01). Although age was not correlated with any of the dependent measures (all
p
-
values>.10) we nonetheless re-ran all the analyses above using age as a covariate. Age was not a
significant covariate in any of the analyses (all
p
-values>.10) and the results replicated our
previous findings of no significant gender differences.

Mating Mechanisms 26
23-1H(A+(0+:.%=#/+<(/3%1(C1/#&<#0<1(+,,+=/G(<%,,+0+&=+(,*0($+&(#&<(A*$+&(,*0(13*0/-term
relationships. But, by pointing to the same effect in long-term relationships, and no difference in
this pattern for men and women for neither positive (Hypothesis 1) nor negative (Hypothesis 2)
traits, these findings overall do not support the proposition of SST that men, more so than
women, "lower" their standards in short-term compared to long-term relationships. The
similarity of men and women in their patterns of responses, however, is consistent with the
viewpoint of AFT.
General Discussion
S
u
mm
ary
!"#$%&'&(#)*+&&(,(&-./0'&1(#02'/(2+&-$%(#-(&+2'(+3(4'5.#$(4-*#-'60'&(78'+*%9&(+*060"#$(
core%assumptions%(Buss%and%Schmitt,%1993),%are%not%consistent%with%the%claim%that%men%and%
women%have%distinct mating mechanisms. We recognize that sometimes theories may morph
*E+0(/%$+_(D&(/3#/(=#1+H(#1(1*$+(3#E+(1-''+1/+<(5+B'BH(`%''%&1H(QRRI6H(/3+(&+A(C$*0:3+<G(/3+*04(
is essentially a new theory, and should be designated with a new label. Meanwhile the original
theory, in this case Sexual Strategies Theory, as specified in Buss and Schmitt (1993), is what is
being evaluated here.
I")+"&0&-'"-(:0-8(4479&(;<.&&(=(4)820--1(>??@A(precis%point%3,%most%men%are%not%more%
apt%to%spend%proportionately%more%of%their%mating%effort%in%short?term%mating.%%Nor%are%they%more%
apt,%compared%to%women,%to%lower%their%standards%in%short?term%compared%to%long?term%mating.%%
Furthermore,%in%short?term%mating,%most%men%are%not%more%apt%to%seek%sex%if%pregnancy%is%likely%
or%feel,%on%the%average,%reproductively%constrained:%And,%in%any%event%women%and%men%exhibit%
the%same%pattern%of%constraint. %

Mating Mechanisms 27
Instead, these findings suggest that when it comes to patterns of preferences and behavior
in short-term versus other mating where Buss and Schmitt (1993) postulated or specifically
predicted that there would be gender differences, there is far more overlap and similarity
between men and women than difference. That pattern of greater gender similarity than
difference in the current findings, is more consistent with Attachment Fertility Theory (AFT)
(Miller & Fishkin, 1997) that would postulate that there would generally be more similarity than
differences between men and women in their evolved mating mechanisms. These findings are
also consistent with the Gender Similarities Hypothesis which states that men and women are
very similar on most variables (Hyde, 2007). Not only has this similarity been shown in the
areas of cognitive abilities and self-esteem, but more relevant to the current paper is the meta-
analytic evidence that most gender differences in sexual behaviors and attitudes are small in
magnitude (Petersen & Hyde, 2010).
SST#versus#AFT:#Key#theoretical#differences#underlying#hypotheses#
Different parental care assu
m
ptions yield different predictions regarding sex-distinct or
s ex-si
m
ilar
m
ating
m
echanis
m
s
. Sexual Strategies Theory and Attachment Fertility Theory both
stress the role of paternal caregiving. As 1/#/+<(#F*E+H(20%E+017(Y#0+&/#.(D&E+1/$+&/(23+*04(
5>?]Q6(#0'-+1(,*0(#(/4:+(*,(C/0#<+-*,,G(F+/A++&(%&E+1/%&'(%&($#/%&'(#&<(%&E+1/%&'(%&(:#0+&/%&'B((
That is, if men (women) devoted more care to their offspring than women (men), men (women)
would be expected to devote less effort to mating than the other gender. Sexual Strategies
Theory (SST), although acknowledging that human fathers often provide considerable care to
their offspring, focuses, as Parental Investment Theory does, on the
relative invest
m
ent that
m
ales and fe
m
ales
m
ake
(Buss & Schmitt, 1993). For SST, these relative care differentials
produced
distinct evolved
m
ating
m
echanis
m
s for
m
en and wo
m
en
with the emergent outcome, it

Mating Mechanisms 28
is argued, that men devote more of their total mating effort than women to short-term mating
(Buss & Schmitt, 1993). The findings in the current work fail to support this claim.
AFT claims that instead of
distinct
critical problems for men and women leading to sex-
distinct evolved mating mechanisms, humans
shared
one of the most fundamental problems that
shaped human evolution, the survival of extraordinarily dependent and vulnerable offspring
(Miller & Fishkin, 1997). Such shared evolved problems for men and women were solved with
evolved mechanisms that operated more similarly than differently for men and women (e.g.,
pair-bonding mechanisms; parental caregiving mechanisms). These evolved mechanisms afford
the formation and maintenance, in humans, of long-term pair-bonds that support survival of
offspring so that offspring might themselves reproduce.
AFT, in contrast to portrayals of AFT (e.g., Schmitt, Shackelford, & Buss, 2001), does
not
argue for or require two parents to be
equally
engaged in childcare and emotional nurturance.
Rather, AFT argues that biparental care (the contribution of both parents in childcare, protection,
support, and socio-emotional nurturance) in humans rather than the care of one parent
enhanced
the survival of offspring (Miller & Fishkin, 1997). AFT argues that in humans, as across
mammals (Wynne-Edwards, 2001), where paternal L as well as maternal -- investment in
offspring enhances their survival (see Miller & Fishkin, 1997; Miller et al., 2005), predominately
homologous rather than sex-distinct caregiving, pair-bonding, and mating preference
mechanisms are likely. Assuming that mating behaviors are not constrained by cultural factors,
AFT predicts greater gender similarity than gender differences in emerging patterns of mating
behavior. The current findings are consistent with those predictions.
What is the place of short-ter
m
m
ating in hu
m
an
m
ating?
SST and AFT do not differ in
assuming that humans exhibit short-term, as well as long-term mating (Miller & Fishkin, 1997).

Mating Mechanisms 29
SST, however, unlike AFT, posits distinct evolved short-term mating mechanisms and that these
were distinct for men and women. In the past, various proponents of SST (e.g., Schmitt,
Shackelford, & Buss, 2001) have argued that specific physiological design features of human
males and females are consistent with short-term mating as an important evolved mating
1/0#/+'4B((23%1(3#1(%&=.-<+<(:*%&/%&'(/*(=.#%$1(0+'#0<%&'(1*(=#..+<(CK%$%a#K++(1:+0$G(5;#K+0(O(
Bellis, 1993). However, these claims were subsequently systematically tested and debunked
(Moore, Martin, & Birkhead, 1999; see also Simmons, Firman, Rhodes, & Peters 2004).
Furthermore, the evidence for underlying biology and chemistry that might support such
sex-distinct mechanisms and how these fit into broader systems of mechanisms is unspecified,
controversial or uncle#0B((P+(#.1*(<*&7/(K&*A(3*A(/3+1+(13*0/-term and long-term systems might
interact (and what would operate for intermediate and other relationships) and exactly how these
distinct underlying biological and chemical mechanisms would differ for men and women.
Furthermore, it is not clear how these sex-distinct sets of mechanisms would develop and
manifest themselves differentially over the life span for human males and females.
In contrast, AFT posits that short-term mating and other forms of mating outside of pair-
bonds
are natural by-products
of a suite of attachment and caregiving mechanisms that, among
other things, were selected for in human evolutionary history to ultimately enable men and
women to seek, select, create, and maintain a pair-bond within which to rear offspring who
would themselves survive to reproduce. There is a growing body of literature across numerous
literatures both for humans and other pair-bonding species that is pointing to an increasingly
coherent picture of the underlying biological and chemical systems involved in mating and
parenting (e.g., Curtis & Wang, 2003; Ziegler, 2000). The attachment and caregiving systems
provide parsimonious suites of underlying biological, chemical, and psychological mechanisms

Mating Mechanisms 30
that generally operate similarly for men and women (Dixson, 1998; Insel, 1997; Goldstein,
2000). These same suites of mechanisms are likely to have analogs in the development of child
attachments to caregivers (Hazan & Zeifman, 1999).
As we discuss elsewhere (Miller et al., 2005), consistent with the work by Hazan and
Zeifman (1999), men and women appear to have similar mechanisms that can afford (but not
guarantee) more long-term pair-bonding. This full suite of mating mechanisms differs from the
suites of mating mechanisms available to many other species (e.g., chimpanzees), for which full-
fledged pair-bonding is not an option. These processes leading up to a long-term pair-bonding
include mechanisms for promiscuous seeking, partner selection, and pair-bond formation (as
well as mechanisms for relationship repair and dissolution). That is, promiscuous seeking of a
mate, that can result in short-term mating, involves the same mechanisms designed to result in
better partner selection: At any point, however, the relationship may fail to advance to a full pair-
bond or even when a pair-bond is formed, may not be maintained over time.
As we have also argued (Miller et al., 2005), differential parameter settings on these
mechanisms and universal motives (e.g., approach and avoid systems) due to a combination of
genetic and experiential factors (e.g., differential caregiving experience and thereby attachment
styles) can make it more or less likely that individuals will forge, maintain, repair and sustain
long-term pair-bonds. For example, when men or women do not feel comfortable being close in
relationships or trusting of their partner (or have a low threshold for rejection), they may
promiscuously seek partners but have more difficulty moving into or being selected into the
more intermediate phase of later pair-bonding stages of relationships. Even if they achieve such
ends, relationships may be more tenuous, more difficult to repair, or they may be quicker to
disengage from the relationship and begin anew (i.e., seeking promiscuously again). The net

Mating Mechanisms 31
effect for this type of individual over time is more time devoted to the promiscuous seeking
phase and more lifetime short-term partners (Miller & Fishkin, 1997; Miller et al., 2005).
We should note that AFT has from its inception (e.g., Miller & Fishkin, 1997) argued that
when critical parameters are absent (e.g., a lack or loss of emotional closeness in the
relationship), human evolved mechanisms would reduce the probability of retaining a single
mate and/or enhance the probabi.%/4(*,(1++K%&'(#(<%,,+0+&/($#/+B((23%1(+$*/%*&#.(1%'&#.H(C,++.%&'1(
*,(=.*1+&+11G(5*0(%/1(#F1+&=+6(%1(#:/(/*(:0*E%<+(#&(%$:*0/#&/(%&<%=#/*0(,*0(F*/3($+&(#&<(A*$+&(#1(
to whether the pair-bond is apt to last, and therefore the likelihood that a pregnancy would result
in a secure biparental environment within which to rear an offspring to adulthood. The
attachment system provides evolved mechanisms for detaching from relationships when those
relationships are less likely to support offspring survival and when seeking new relationships are
more apt to do so. Still, the bottom line in evolution is offspring survival and their own
reproduction of offspring as adults. Clearly, more systematic work is needed to assess in hunter-
gatherers the links between pair-bonding patterns and lifetime offspring survival to reproduction.
The I
m
pact of
S
exual Experience, Culture, and
S
ocial Roles
AFT argues that we would expect relatively few evolved differences between men and
women in underlying mechanisms producing emergent outcomes in mating behavior. However,
we may still find gender differences in mating behavior and this may vary across cultures. What
might be responsible for such differences if they are not due to evolutionary factors?
Obviously it is important to disconfound biological sex from experiential factors. What
are those experiential factors? First, if men are exposed to more sexual materials (Kenrick,
Neuberg, Zierk, & Krones, 1994), and cultural stereotypes differentially prepare males and
females for sex,
s exual experience
might be an important moderator of gender difference

Mating Mechanisms 32
reactions to sexual stimuli. With sexual experience, both males and females are apt to adjust
their beliefs, goals, and reactions to sexual and emotional stimuli to be more in line with their
actual experiences: Prevailing cultural norms and stereotypes are apt to play less of a role in their
reactions.
Harris (2000) examined this possibility. She found that women who had experience with
a committed sexual relationship displayed greater physiological reactivity to sexual relative to
emotional infidelity (a pattern similar to men) whereas the opposite pattern tended to hold true
for females without such experience. Thus, this work suggests an important control or moderator
variable (e.g., sexual experience) for researchers examining gender differences in this domain to
examine. Contrary to predictions from Sexual Strategies Theory, men and women with sexual
experience showed a similar pattern of physiological reactivity.
Second, individuals may differ in their experience due to culturally imposed constraints.
A number of authors have argued (Eagly & Wood, 1999; Hrdy, 1999; Kasser & Sharma, 1999),
that a variety of cultural factors may impact gender differences in the focus on a mate71(0+1*-0=+1(
(e.g., money, status). For example, Kasser and Sharma (1999) noted that a number of theorists
(e.g., Caporael, Dawes, Orbell, & Van de Kragt, 1989; Hrdy, 1999) have proposed females may
value a partner with money and status because these women live in societies where they are
unable to obtain these resources themselvesB((;-/H(;-11(#0'-+<(/3#/(/3+(+#0.%+0(C1/0-=/-0#.(
:*A+0.+11&+11G(34:*/3+1%1(5;-11(O(;#0&+1H(>?S^6H(%B+B(C/3+(&*/%*&(/3#/(%&(=-./-0+1(A3+0+(,+$#.+1(
have economic equality, the diff+0+&=+1(F+/A++&($+&71(#&<(A*$+&71($#/+(:0+,+0+&=+1(13*-.<(
<%$%&%13G((58#11+0(O()3#0$#H(>???H(:B(@]I6(3#1(&*/(F++&(1-::*0/+<(#&<(,%&<%&'1(/*(<#/+(3#E+(
been inconsistent with hypotheses of culture-based differences. For example, Buss (1989) found
no relationship between economic inequality and mate preferences. And Wiederman and

Mating Mechanisms 33
Allgeier (1993) and Townsend (1989) found, in fact, a positive rather than negative correlation
between economic equality and education and desire for mate wealth.
However, Kasser and Sharma (1999) argue that those testing the cultural hypothesis have
under emphasized the means by which women around the globe may enhance their economic
equality. They argue that in order to be financially self-sufficient, women need to be able to
control their fertility (e.g., plan pregnancies) and have access to education (e.g., the means by
which they can gain economic security). Without the ability to control their own fertility and
gain access to education, women may be more dependent upon men for the resources that they
need for themselves and their offspring. In such cases, Kasser and Sharma (1999) argue that
women will particularly value cues signaling such economic potential in a mate.
8#11+0(#&<()3#0$#71(5>???6(<#/#H(=*..+=/+<(,0*$(@](=-./ures, supported the hypothesis
that a lack of other sources of power, such as education or reproductive care, might lead women
to feel they lack control over their own lives. As a result, they would be inclined to value cues in
a mate which signal resource acquisition. Indeed, they find that women are more likely to desire
resource acquisition characteristics in mates when: they have less educational equality, use
contraception less, don't have laws regarding domestic violence, and have lower literacy
equality.
Eagly and Wood (1999), concurrently examining the same data set, also examined a
E#0%+/4(*,(%&<%=#/*01(*,(A*$+&71('+&<+0(+$:*A+0$+&/B(23%1(%&=.-<+<(/3+(&-$F+0(*,($#&#'+0%#.(
positions, proportion of earned income, and number of parliamentary seats. They also assessed
gender related development propensity (e.g., ability of nations to provide health care, access to
educational and financial equality for women). Those mating preferences that were associated
with traditional gender role divisions of labor (e.g., good earning capacity of male bread winner;

Mating Mechanisms 34
good housekeeper) showed sharper gender differences in those cultures where there was less
gender empowerment and related development. Kasser and Sharma (1999) found similar results
when they examined similar cultures. Wood and Eagly (2002) assessed the importance of
economic and socio-structural factors in societies (in particular, female reproductive capacity),
and conclude that men and women are able to adapt to a variety of labor roles that do not fall
along stereotypical gender lines (2002). Relatedly, Eagly and Wood found that with more gender
equality across nations, gender differences in the preferred age differential of a mate were
reduced (1999). More generally, traditional gender ideology appears to be positively related to
sex-typed mate preferences (Johannesen-Schmidt & Eagly, 2002; Koyama, McGain, & Hill,
2004).
Overall, while it is apparent that women (and probably men as well) have probably
always been concerned with securing resources for themselves and their children, their
environment and cultural situation may determine exactly where and how women plan for and
secure those resources (Hrdy, 1999). That is, if the culture restricts women's access to resources
to those provided by men, then women will value characteristics in men that afford those
resources; this is especially likely to be the case when women do not have control over their own
reproduction.
Yet another factor that can impact mating behavior are gender schemas. As discussed in
Signorella and Frieze (2008), gender schemas may influence behavior, attitudes, and preferences
by providing ideas for what is appropriate for both males and females. In a related vein, Social
Role Theory (Eagly & Wood, 1999) attributes gender differences in mating preferences largely
to the gender roles imposed or promoted by society. Consistent with this viewpoint, Alexander
and Fisher (2003) tested whether gender differences in self-reported sexual behavior might be

Mating Mechanisms 35
influenced by gender norms. They found that gender differences were attenuated in a bogus
pipeline condition where participants believed that false responding could be detected. In
addition, not only do these roles vary across culture (and can thus account for some cross cultural
variance in mating behavior and preferences) but individuals within a culture can vary in the
extent to which they believe in or adopt such roles.
Conclusions and Future Directions
Several important assumptions of Sexual Strategies Theory dealing with proportional
mating effort, sexual constraints, and standards for a mate were not supported by findings
reported in the current work. If we are to develop useful evolutionary models of psychological
phenomena, we must insist on more thorough, adequate, and direct tests of a given evolutionary
/3+*0471(F#1%=(#11-$:/%*&1(0+'#0<%&'(<%,,+0+&=+1(F+/A++&($+&(#&<(A*$+&(L let alone
evolved
sex-differences. When doing so, it might be useful to better delineate if and how the
distributions for men and women overlap: That is, is the amount of overlap in distributions for
men and women high and the within gender variability greater than between gender variability?
And, where there is large within gender variability, what are the dynamics that produce this? To
the extent that this is the case it behooves researchers to explain the underlying system of sex-
distinct mechanisms that can produce such variability. For example, as we noted in our earliest
AFT work, those men who had more distant relationships with their fathers (lowest quartile) had
remarkably higher levels of desired sexual partners compared to other men and compared to
most women (Miller & Fishkin, 1997). Similar to these findings, Willis and Clark (2009) report
that higher levels of paternal caregiving and warmth are associated with an increased likelihood
of men being in a monogamous relationship relative to men with cold or absent fathers.

Mating Mechanisms 36
Where theorists make claims about underlying evolved differences in sex-distinct
mechanisms, those claims clearly L at some point -- need to be accompanied with (and linked to)
evidence for corresponding underlying differences (for men
and
women) in human biological
and/or chemical design and mechanism. Our evolutionary approaches to human mating
psychology, must be embodied and fit with our knowledge of sexual functioning, fertility, and
related systems.
In this regard, it is noteworthy that there has been some increased attempt to look at
changing preferences, for example, during the menstrual cycle and their implications for extra-
pair mating that take biological and chemical parameters better into account (e.g., Gangestad,
Simpson, Cousins, Garver-Apgar, & Chrisetnsen, 2004). These findings, however, are likely to
fit with the argument we made earlier (Miller & Fishkin, 1997) that when long-term relationships
are not possible or difficult to forge and maintain, both women and men may engage in short-
term relationships. As such, individuals may seek both types of relationships over time, in part,
because either at a specific point in time or chronically they were not able to maintain enduring,
emotionally close, long-term relationships. Nevertheless, these emergent outcomes are unlikely
to require distinct evolved design features beyond those afforded by the same basic evolutionary
designed suites of attachment and caregiving systems that afford mate seeking, selection, and
long-term pair-bonding. Understanding human psychological, biological, and chemical systems
as systems is key L as are the needed tools (e.g., computational modeling) to achieve better
understanding of the underlying system dynamics.
In doing so, we must also more systematically consider how environmental and
experiential factors interact with differences found for men and women (either in terms of
measures of central tendency and in distributional differences) and how human systems depart

Mating Mechanisms 37
from those of other species systems, and why. A useful evolutionary dynamics will be one that
systemically considers and predicts the mutual influences between design and our changing
social and material worlds, and the affordances, constraints, and challenges that our past presents
for our present and future.

Mating Mechanisms 38
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Mating Mechanisms 44
Author Note
Correspondence may be sent to either William C. Pedersen, Department of Psychology,
California State University, Long Beach, 1250 Bellflower Boulevard, Long Beach, CA 90840-
0901 or Lynn Carol Miller, Annenberg School for Communication, University of Southern
California, Los Angeles, CA 90089-0281. Electronic mail may be sent to either
wpederse@csulb.edu or Lmiller@usc.edu.

Mating Mechanisms 45
Table 1
Mean Participant Age and the Proportion of Mating Effort (both Time and Money)
Dedicated to Short-Term Relationships using both Open-Ended (OE) and
Fixed Scale (FS) Formats (Study 1)
___________________________________________________________________
Gender Age Time (OE) Money (OE) Time (FS)
a
Money (FS)
b
___________________________________________________________________
Male 20.83 .30 .25 .32 .31
Female 19.56 .24 .17 .30 .30
___________________________________________________________________
a
Scale values ranged from 1 ("no time at all") to 6 ("eight or more hours a weekG6
b
Scale values ranged from 1 ("no money at all") to 7 ("over $100")

Mating Mechanisms 46
Table 2
Mean Participant Age and the Desire to Seek or Avoid
Pregnancy in Short- and Long-Term Relationships (Study 2)
__________________________________________________
Gender Age Short-Term Long-Term
Relationships
a
Relationships
a
__________________________________________________
Male 19.52 -2.03 -0.58
Female 19.32 -2.29 -1.04
__________________________________________________
a
)=#.+(E#.-+1(0#&'+<(,0*$(b@(5Cvery actively seekG6
to -3 ("very actively avoid") pregnancy

Mating Mechanisms 47
Table 3
Mean Participant Age and the Desirability of Positive and Negative Traits
a
in a
Romantic Partner for both Short-Term (ST) and Long-Term (LT) Relationships (Study 4)
________________________________________________________________________
Gender Age Positive (ST) Positive (LT) Negative (ST) Negative (LT)
________________________________________________________________________
Male 19.58 1.14 1.41 -1.53 -2.03
Female 19.07 1.61 1.87 -1.91 -2.35
________________________________________________________________________
a
Scale values ranged from -3 (Chighly undesirableG) to +3 (Chighly desirableG)

Mating Mechanisms 48
Figure Caption
Figure 1
. Frequency of the Constraint values (viz. ideally desired number minus expected
number of sexual partners) for the 30-year time period (Study 3). High positive numbers
reflected constraint with ideal scores greater than expected scores.

Mating Mechanisms 49
0
20
40
60
80
100
120
-50
-30
-10
-8
-6
-4
-2
0
2
4
6
8
10
30
50
Frequency
Constraint (Ideally desired minus Expected number of Partners)
Males
Females