Prenatal exposure to sex hormones predicts gratitude intervention use.
Examination of digit ratio, motivational beliefs, and online activities
, Lukasz D. Kaczmarek
, Todd B. Kashdan
, Marcin Zimny
, Hubert Urban
, David Disabato
Adam Mickiewicz University, Poland
George Mason University, United States
Received 25 October 2014
Received in revised form 20 December 2014
Accepted 22 December 2014
Men are less grateful than women and less likely to intentionally enhance gratitude via interventions.
Yet, little is known if sex differences in gratitude result from biological inﬂuences such as prenatal tes-
tosterone and estrogen levels – hormones that control the development of sex-speciﬁc characteristics.
In two studies, we examined how sex and second-to-fourth digit ratio (2D:4D) – an indicator of prenatal
sex hormones exposure – predicts gratitude intervention use. In the ﬁrst study, we tested whether lower
2D:4D (i.e., higher masculinization) would suppress gratitude intervention use. Contrary to expectations,
after controlling for sex, women and men with more male-type ﬁngers were more motivated and likely to
complete the intervention. In the second study, we replicated these ﬁndings using a larger sample and
different 2D:4D metric. Our research suggests that motivation towards gratitude interventions is facili-
tated by female sex and masculinity. These ﬁndings provide initial evidence for the biological grounding
of individual differences in gratitude behavior.
Ó2015 Elsevier Ltd. All rights reserved.
Men are generally less grateful than women and endorse
greater difﬁculties expressing gratitude; with small to medium
effect sizes of these phenomena (Kashdan, Mishra, Breen, & Froh,
2009). Furthermore, men perceive self-administered gratitude
interventions to be more difﬁcult to perform (Kaczmarek
Kashdan, Dra˛ _
zkowski, Bujacz, & Goodman, 2014). Yet, little is
known about the extent to which sex differences in gratitude
expression stem from biological factors such as exposure of the
fetus to testosterone and estrogen. Prenatal hormones that control
the development of sex-speciﬁc characteristics are among the ﬁrst
inﬂuences in ontogenesis that contribute to differences in psycho-
logical and behavioral outcomes observed in later life (MacLusky,
Bowlby, Brown, Peterson, & Hochberg, 1997; Manning, 2011). We
extended prior studies on gratitude interventions (Huffman et al.,
2014; Kaczmarek, Kashdan, et al., 2014) by examining potential
biological antecedents of the motivation to expand opportunities
for greater gratitude experiences and expression. Understanding
why individuals endorse or reject opportunities to become more
grateful is vital for the provision of individually tailored health
1. Gratitude interventions
Grateful feelings result from the belief that one has obtained a
beneﬁt attributable to the actions of another person or some
impersonal source (McCullough, Emmons, & Tsang, 2002).
Although some gratitude interventions encourage people to thank
benefactors in their lives (Lambert & Fincham, 2011), these inter-
personal exchanges are often viewed as burdensome (Huffman
et al., 2014). For this study, we used an intervention that required
people to recognize and express beneﬁcial daily experiences in a
journal (Emmons & McCullough, 2003).
Only a fraction of individuals who are given an opportunity to
initiate a free gratitude intervention program translate their inten-
tions into practice (Kaczmarek et al., 2013). Yet, individuals with
high intentions to change are about twice as likely to initiate a
gratitude intervention successfully. High intenders derive their
motivation from beliefs about the intervention’s personal useful-
ness (utility beliefs), sense of approval from others upon attending
to gratitude (social norm beliefs), and to a lesser extent – from the
perceived feasibility/difﬁculty of the intervention (self-control
beliefs; Kaczmarek, Kashdan, et al., 2014). These three motiva-
tional components, based on the theory of planned behavior
(TPB; Ajzen, 1991, 2011), provide a useful framework for the study
of self-motivated gratitude exercises.
0191-8869/Ó2015 Elsevier Ltd. All rights reserved.
Corresponding author at: Institute of Psychology, Adam Mickiewicz University
´, 89 Szamarzewskiego Street, PL-60-568 Poznan, Poland.
E-mail address: firstname.lastname@example.org (M. Misiak).
Personality and Individual Differences 77 (2015) 68–73
Contents lists available at ScienceDirect
Personality and Individual Differences
journal homepage: www.elsevier.com/locate/paid
2. Sex differences in gratitude
Previous studies revealed that compared with men, women are
more motivated to participate in gratitude interventions because
they expect gratitude expression to be more useful and socially
desirable (Kaczmarek, Kashdan, et al., 2014; Kaczmarek et al.,
2015). This ﬁnding complements general evidence that women
are more likely to feel and express gratitude and derive more ben-
eﬁts from gratitude expression (Kashdan et al., 2009). The early
emergence of sex differences in gratitude expression and its stabil-
ity across the life-span (Becker & Smenner, 1986; Krause, 2006)
suggest that sex differences might be initiated by biological factors
and not just social inﬂuences.
3. Second-to-fourth digit ratio
Understanding the long-term psychological consequences of
prenatal exposure to sex hormones (testosterone and estrogen)
became feasible after second (index ﬁnger) to fourth digit (ring ﬁn-
ger) length ratios (2D:4D) received validation as an indicator of
early hormonal inﬂuences (Manning, Scutt, Wilson, & Lewis-
Jones, 1998). Resulting 2D:4D arises from variation in the length
of the fourth digit that is particularly rich in androgen and estrogen
receptors and thus more sensitive to inﬂuences from these hor-
mones (Zheng & Cohn, 2011). Noteworthy, 2D:4D is unrelated to
adult sex hormones levels (Hönekopp, Bartholdt, Beier, & Liebert,
Several studies indicated that lower 2D:4D is predictive of
masculine psychological outcomes. Experimental studies with
mammals reveal that lower 2D:4D results from stronger masculin-
ization and defeminization prenatal processes (i.e., exposure to
higher levels of prenatal testosterone relative to estrogen; Zheng
& Cohn, 2011). For instance, girls with low 2D:4D show less prefer-
ence for female-typical toys (e.g., baby dolls) and are more active
during play (Alexander & Saenz, 2012), whereas boys show more
preference for male-type plays (e.g., play-ﬁghting, ball games)
(Hönekopp & Thierfelder, 2009). Women with low 2D:4D tend to
identify with male-type sex roles (Csathó et al., 2003), whereas
men tend to be more dominating (Meij, Almela, Buunk, Dubbs, &
Salvador, 2012) risk-taking (Stenstrom, Saad, Nepomuceno, &
Mendenhall, 2011), and sensation-seeking (Fink, Neave, Laughton,
& Manning, 2006). Despite these ﬁndings, a meta-analysis indicated
that the correlations between 2D:4D and masculinity/femininity
personality dimensions are not robust and 2D:4D explains only a
small fraction of variance (Voracek, Pietschnig, Nader, & Stieger,
4. The present study
We examined whether 2D:4D predicts motivation in and actual
performance of a self-initiated gratitude intervention. Based on
prior studies (Kaczmarek et al., 2013; Kaczmarek, Goodman,
et al., 2014) we examined whether women, and in particular
women exposed to lower prenatal androgen levels (higher
2D:4D) show greater participation in gratitude interventions. We
expected less masculinized (higher 2D:4D) men and more femi-
nized women to be more likely to initiate a gratitude intervention.
Furthermore, we expected behavioral intentions to be enhanced by
higher utility beliefs and more accepting social-norm beliefs. These
motivational beliefs were hypothesized to mediate between sex
and 2D:4D and actual intervention participation. Accounting for
markers of biological formative inﬂuences (2D:4D), in addition to
sex of the participant (reﬂecting a compound of biological and
social inﬂuences), allows for a better understanding of how indi-
vidual differences affect gratitude expression.
5. Study 1
Participants were 279 undergraduates from natural science, life
science, and technical departments (71% female) between the ages
18 and 28 years (M= 21.19, SD = 1.71). Students were recruited
before classes by experimenters to a study on well-being. Volun-
teers received no incentives for their participation. Missing values
(0.6%) were determined to be random, Little’s test
(50) = 49.32,
p> .05, and imputed with Expectation–Maximization method
(Enders, 2001). Written informed consent was obtained from each
Having read leaﬂets about the gratitude intervention, partici-
pants reported utility beliefs, social norm beliefs, and self-control
beliefs regarding this intervention. They were informed that if they
provided their e-mail address they could receive an online invita-
tion for a free intervention. Next, we measured behavioral inten-
tions towards the intervention and took photos of their hands
with digital cameras. The invitation with the link to the interven-
tion website was e-mailed the next day, and follow-up reminders
were sent three days after completion of each entry.
We used four scales to measure utility, social norm, self-control
beliefs, and behavioral intentions scales formulated according to
guidelines provided by theory of planned behavior (TPB) and vali-
dated in prior studies (Kaczmarek, Goodman, et al., 2014;
Kaczmarek, Kashdan, et al., 2014).
Utility beliefs, or attitudes about likely consequences of the grat-
itude intervention, were assessed with three items on a 7-point
bipolar evaluative adjective scale: ‘‘unpleasant–pleasant’’, ‘‘bad–
good’’, and ‘‘useless–useful’’ (
Social norm beliefs, or beliefs about what signiﬁcant others
might think about participating in the intervention, were assessed
with three items, e.g., ‘‘Most people who matter to me would
approve my doing this intervention.’’ Participants responded to
items on a 7-point scale from 1 = ‘‘completely disagree’’ to
7 = ‘‘completely agree’’ (
Self-control beliefs, or beliefs about being able to effectively han-
dle the intervention exercises, were measured with three items,
e.g., ‘‘Performing this intervention would be very easy for me.’’ Par-
ticipants responded to items on 7-point scale from 1 = ‘‘completely
disagree’’ to 7 = ‘‘completely agree’’ (
Behavioral intentions were assessed with three items about spe-
ciﬁc actions in the intervention. Preceded by the phrase ‘‘I intend
to...’’ items included the following actions: ‘‘try out this activity’’,
‘‘start this activity’’, and ‘‘practice this activity’’. Participants
responded to items on 7-point scale from 1 = ‘‘completely dis-
agree’’ to 7 = ‘‘completely agree’’ (
Behavior: A value of 1 was assigned to those participants who
completed a daily entry as logged by the intervention application,
and a value of 0 was assigned if no Internet activity was observed.
Digit ratio: We used digital photos of the right hand (Hönekopp
& Watson, 2010) in a resolution of 3072 2304 pixel to measure
length of the index and the ring ﬁnger using the GNU Image
Manipulation Program (GIMP) and its ‘‘measure’’ tool. Ratios were
calculated by dividing the length, in pixels, of the second digit by
the length of the fourth digit. The measurements performed by
three independent raters were very reliable as indicated by the
M. Misiak et al. / Personality and Individual Differences 77 (2015) 68–73 69
intraclass correlation coefﬁcient, r= .97, thus we averaged them
into one variable.
5.4. Gratitude intervention
Following the paradigm outlined by Emmons and McCullough
(2003), participants were asked to write about up to ﬁve things
that happened to them in the last three days that evoked gratitude.
Participants were asked to do this three times, with three days
between each entry. Participants completed this through a dedi-
cated website that provided instructions on how to submit entries
(Yardley et al., 2009).
5.5. Analytical strategy
We used structural equation modeling in Mplus 7.2 (Muthén &
Muthén, 2012) to test if behavior was predicted by intentions,
intentions by TPB components, and TPB components by sex and
2D:4D. TPB (Ajzen, 2011) assumes a full mediation between back-
ground variables (sex and 2D:4D) and subsequent components.
As 2D:4D has different effects for men than women (Fink et al.,
2006), we introduced the interaction term 2D:4D (centered) sex
as a predictor of TPB components. To account for the binary out-
come (completion of the gratitude intervention vs no completion)
we used weighted least-square with mean and variance correction
estimator (WLSMV; Muthén & Muthén, 2012). Linear regression
was used for continuous and probit regression for binary dependent
variables. The residual variance of TPB variables was freed to corre-
late amongst each other in line with the TPB theory (Ajzen, 1991)
and previous SEM models with endogenous TPB variables
(Kaczmarek, Kashdan, et al., 2014). To evaluate model ﬁt we calcu-
lated RMSEA, which is recommended for the WLSMV estimator,
with values <.06 indicating good ﬁt (Yu & Muthén, 2002). We also
computed the Comparative Fit Index (CFI) as a secondary parameter
with values above .95 indicating good models (Hu & Bentler, 1999).
Bias-corrected bootstrapping with 5000 bootstrap samples was
used to test indirect effects (products of unstandardized coefﬁ-
cients). Bootstrapping produces point estimates and conﬁdence
intervals (CI) for the indirect effects. Signiﬁcant indirect effects
are indicated by CIs that do not include zero: 99% CI is equivalent
to p< .01, 95% CI to p< .05, and 90% CI to p< .10 (Hayes, 2013).
We present coefﬁcients of determination to inform the variance
contributed by predictors to account for dependent variables.
Descriptive statistics along with inter-correlations between
study variables are presented in Table 1. The difference in 2D:4D
between men (M= 0.982, SD = .046) and women (M= 0.985,
SD = .046) was not signiﬁcant, t(277) = 0.58, p> .05. Of the partici-
pants, 58 women and 19 men self-initiated (27.6%) and 22 women
and 3 men completed (8.9%) the intervention.
The model (Fig. 1) ﬁt the empirical data well,
(107) = 141.43,
p< .05, RMSEA = .03, 90% CI [.02, .05], CFI = .96. Women and indi-
viduals with a lower 2D:4D endorsed greater utility beliefs and
social norm beliefs, and these beliefs, in turn, predicted grateful
behavior. Furthermore, there was a direct effect of sex on inten-
tions, and a marginal effect of 2D:4D on intentions.
The interaction between 2D:4D and sex failed to signiﬁcantly
predict other variables in the model. Exclusion of these paths had
no effect on the model ﬁt,
(6) = 6.82, p> .05. Women were
more likely to complete the intervention with indirect effects via
intention, b= 0.07, 99% CI [0.02, 0.16], utility beliefs and intention,
b= 0.02, 99% CI [0.01, 0.05], and social norm beliefs and intention,
b= 0.02, 95% CI [0.01, 0.05]. Individuals with lower 2D:4Ds were
more likely to complete the intervention as indicated by indirect
effects operating through utility beliefs and intention, b=0.27,
95% CI [0.76, 0.04], and a marginal indirect effect via intention,
b=0.66, 90% CI [1.52, 0.03] and social norm beliefs and inten-
tion, b=0.34, 90% CI [0.87, 0.04].
In this study we found that participants’ 2D:4D provided addi-
tional information above that conveyed by their sex. As was the
case in previous studies (Kaczmarek et al., 2013), women were
more likely to self-initiate and complete a gratitude intervention.
Yet contrary to our expectations more masculinized men and less
feminized women (lower 2D:4D) perceived this intervention as
more useful and socially endorsed. Their motivational beliefs
translated into actual performance of the intervention.
6. Study 2
The results of Study 1 had a few effects that were contrary to
expectations. In the next study, we aimed to replicate these ﬁnd-
ings using a larger sample and a different 2D:4D measurement
technique. Replication of unexpected results is necessary to deter-
mine the stability of the model. In Study 2, we focused on behav-
ioral intentions because the value of intentions in predicting
actual gratitude intervention participation was established in
Study 1, as well as previous projects (Kaczmarek et al., 2013;
Kaczmarek, Goodman, et al., 2014).
Participants were 736 individuals (75.5% women) aged between
18 and 55 years (M= 21.66, SD = 4.33), who completed a web-
based survey. The invitation was placed on a health psychology
Facebook proﬁle and shared by its subscribers within their social
networks reaching the scope of 40,756 users. Data were missing
at random (0.4%),
(104) = 124.79, p> .05, and imputed with
Expectation–Maximization algorithm (Enders, 2001).
Psychometrics: We used Study 1 measures for utility beliefs
= .86), social norm beliefs (
= .90), self-control beliefs
= .94), and behavioral intentions (
= .98). Participants were free
to keep a gratitude journal on their own; online templates were
not provided in this study.
Digit ratio: Participants were asked to use a ruler available at
their household and measure index and ring ﬁnger with a millime-
ter precision, palm facing upwards, ﬁngers outstretched, from ﬁn-
ger tip to the middle of the proximal crease at the base of the ﬁnger
(Hönekopp, 2011). They were provided with a graphic illustration
of how to measure their ﬁngers correctly. As self-measured
2D:4D is prone to produce outliers, we inspected the dataset and
indentiﬁed 4 individuals with z-scores below and 5 above the
3.29 threshold (Tabachnick & Fidell, 2007). We ran the same model
with and without outliers in the dataset to test if the results were
robust to extreme scores.
6.3. Data analysis
We used structural equation modeling with the maximum like-
lihood estimator to test if intentions were predicted by TPB compo-
nents, sex, and 2D:4D. To evaluate the ﬁt of the model we
calculated RMSEA, CFI, and SRMR (values <.08 indicative of a good
ﬁt; Hu & Bentler, 1999). We used the same bootstrapping approach
to test indirect effects as in Study 1.
70 M. Misiak et al. / Personality and Individual Differences 77 (2015) 68–73
Descriptive statistics and inter-correlations are presented in
Table 2. The difference in 2D:4D between men (M= 0.993,
SD = 0.046) and women (M= 0.999, SD = .044) was not signiﬁcant,
t(734) = 1.50, p> .05. The model (Fig. 2) ﬁt the empirical data
(79) = 178.22, p< .01, RMSEA = .04, 90% CI [.03, .05],
CFI = .99, SRMR = .03. Exclusion of outliers did not affect any ﬁt
index or any coefﬁcient, indicative that the sample was large
enough to buffer against suspicious scores. Sex and marginally
2D:4D predicted the TPB components, especially utility beliefs that
in turn, increased behavioral intentions.
The interaction term (2D:4D Sex) failed to signiﬁcantly pre-
dict other variables in the model. Exclusion of these paths had no
effect on the model ﬁt,
(7) = 3.88, p> .05. Women were more
likely to endorse higher behavioral intentions via utility beliefs,
b= .25, 99% CI [.14, .37], and social norm beliefs, b= .04, 99% CI
[.01, .09]. Individuals with lower 2D:4D had stronger intentions
due to their utility beliefs, b=2.90, 99% CI [5.14, 0.97], and
marginally social norm beliefs, b=0.42, 90% CI [0.99, 0.07].
We found that lower 2D:4D predicted greater utility beliefs, i.e.,
more masculinized men and less feminized women expected more
beneﬁts from a gratitude intervention. The effects of 2D:4D added
to the effects of sex, i.e., after controlling for 2D:4D women were
still generally more motivated to perform the intervention as a
function of utility beliefs and social norm beliefs. Noteworthy,
there was an additional direct effect of sex on intention. This sug-
gests that the TPB does not fully account for the association
between sex and behavioral intentions.
7. General discussion
Previous research documented that women are more grateful
(Kashdan et al., 2009) and incline to stretch their gratitude further
with gratitude interventions (Kaczmarek et al., 2013). Nonetheless,
Descriptive statistics and inter-correlations among Study 1 variables.
1. Utility beliefs
2. Social norm beliefs .48
3. Self-control beliefs .22
4. Intention .47
5. Digit ratio .11 .08 .01 .11
6. Sex .15
.12 .02 .25
7. Behavior – ﬁrst visit .11 .12 .05 .24
8. Behavior – last visit .06 .13
M14.14 12.61 14.41 13.67 0.984 – –
SD 3.35 3.66 3.97 5.04 0.046 – –
Note: Sex coded as 0 = men, 1 = women.
Fig. 1. The effect of sex and second-to-fourth digit ratio on motivation and performance of a gratitude intervention in Study 1 (standardized coefﬁcients). Notes: The percent
of explained variance (R
) is presented in the top right corner for each dependent variable.
Descriptive statistics and inter-correlations among Study 2 variables.
1. Utility beliefs
2. Social norm beliefs .48
3. Self-control beliefs .29
4. Intention .58
5. Digit ratio .12
.06 .02 .07
6. Sex .22
M14.71 12.03 13.48 9.68 0.997
SD 3.55 3.99 4.36 5.64 0.044
Note: Sex coded as 0 = men, 1 = women.
M. Misiak et al. / Personality and Individual Differences 77 (2015) 68–73 71
there has been an absence of research on the biological anteced-
ents of motivation for and participation in gratitude interventions.
In two studies we found that, after controlling for sex, individuals
with more male-type ﬁngers (lower 2D:4D) were more likely to
perceive gratitude behaviors as useful and socially approved. These
beliefs translated into more successful initiation and completion of
a gratitude intervention.
We found that women were more motivated to participate in the
intervention than menbut interestingly, less feminized women were
the most motivated. The same pattern emerged for men, i.e., more
masculine men were more motivated. This ﬁnding adds to prior
study results that focused exclusively on sex (Kaczmarek et al.,
2013) and recent theorizing on the non-binary nature of sex and
the multiple dimensions that comprise gender identity
(Killermann, 2013). However,these ﬁndings contradict a straightfor-
ward expectation that the expression of gratitude via positive psy-
chology interventions is preferred by women compared with men.
These ﬁndings suggest that motivation towards gratitude interven-
tions is inﬂuenced by both female gender and biological male-ness.
Higher motivation towards gratitude interventions among indi-
viduals with lower 2D:4D can have several explanations. First,
women and men with higher 2D:4Ds are prone to depression
(Bailey & Hurd, 2005; Smedley, McKain, & McKain, 2014), and
depressed individuals tend to maintain weaker intentions to initiate
approach behaviors such as gratitude interventions (Kaczmarek
et al., 2013). This might suggest that despite women expecting more
beneﬁts from the intervention (the effect of sex), there might have
been a higher occurrence of depressed individuals among more fem-
inized participants (the effect of 2D:4D). Second, individuals with
low 2D:4D tend to be more energetic and willing to risk more
(Alexander & Saenz, 2012; Fink et al., 2006; Meij et al., 2012;
Stenstrom et al., 2011). These individuals may be more likely to try
and enjoy new activitiessuch as the proposed gratitude intervention.
These current studies have practical implications. Health pro-
fessionals use gratitude interventions as a tool to enhance clients
well-being (Seligman, Rashid, & Parks, 2006; Sin & Lyubomirsky,
2009) and lay-people use them for self-help purposes via profes-
sional resources (Bolier et al., 2013; Schueller & Parks, 2014). Our
work presents meaningful individual differences that inﬂuence
motivations for these interventions (Kaczmarek, Kashdan, et al.,
2014). Understanding and inﬂuencing recipients’ motivations is
imperative, because highly motivated individuals reap more bene-
ﬁts from gratitude expression (Lyubomirsky, Dickerhoof, Boehm, &
Sheldon, 2011; Proyer, Wellenzohn, Gander, & Ruch, 2014) and are
more likely to complete interventions (Schueller, 2010). The cur-
rent project suggests that masculinization may be an overt indica-
tor of greater willingness to participate in gratitude interventions.
This initial evidence, however, needs further studies in applied
There are limitations to our studies. First, we did not address
the outcomes of gratitude expression. Although being more grate-
ful is valuable and pleasant on its own (McCullough, Kilpatrick,
Emmons, & Larson, 2001), it would be interesting to see how
2D:4D inﬂuences gratitude intervention’s outcomes such as well-
being (Krejtz, Nezlek, Michnicka, Holas, & Rusanowska, in press;
Parks, Della Porta, Pierce, Zilca, & Lyubomirsky, 2012) and social
relationship quality (Lambert & Fincham, 2011). Second, we
focused on intraindividual gratitude cultivation in a journal rather
than on communicating grateful feelings to benefactors. The
results for interpersonal expression might be different, because
being thankful to others is more demanding than writing journals
(Kaczmarek, Kashdan, et al., 2014). Third, despite being statistically
signiﬁcant predictors of beliefs, sex and 2D:4D explained only a
small fraction of variance. This ﬁnding is consistent with meta-
analyses that indicate that the effect of 2D:4D is not the major con-
tribution to psychological outcomes (Voracek et al., 2011). Fourth,
the TPB proposed that motivational beliefs resultant from back-
ground variables such as gender (Ajzen, 2011). Yet, TPB does not
explain how background variables translate into speciﬁc beliefs.
Further studies might explore the missing links between 2D:4D
and gratitude beliefs and behaviors. Finally, despite successful
studies where participants self-measured their ﬁngers
(Hönekopp, 2011), such measurements could have been less reli-
able. Moreover, some participants in such studies might have
found information how to interpret 2D:4D, that could bias
responses, e.g., facilitating reactance. Despite such inﬂuences being
possible, results of Study 2 (online) are the same as Study 1 (face-
to-face). Thus, our ﬁndings documented that self-measurements
yield results similar to digital pictures analysis. Our work adds to
the importance of understanding personality and interventions to
change one’s personality from the simultaneous exploration of
psychological and biological levels of analysis.
The studies were conducted in accordance with guidelines pro-
vided by Institutional Ethics Committee.
Fig. 2. The effect of sex and second-to-fourth digit ratio on motivation to perform a gratitude intervention in Study 2 (standardized coefﬁcients). Notes: The percent of
explained variance (R
) is presented in the top right corner for each dependent variable.
72 M. Misiak et al. / Personality and Individual Differences 77 (2015) 68–73
The authors would like to thank Aleksandra Krajczewska, Syl-
wia Madej, Urszula Taczanowska, Weronika Sobczak, and Michał
Kosakowski for assisting with data collection.
Ajzen, I. (1991). The theory of planned behavior. Organizational Behavior and Human
Decision Processes, 50, 179–211.
Ajzen, I. (2011). The theory of planned behavior: Reactions and reﬂections.
Psychology & Health, 26, 1113–1127.
Alexander, G. M., & Saenz, J. (2012). Early androgens, activity levels and toy choices
of children in the second year of life. Hormones and Behavior, 62, 500–504.
Bailey, A. A., & Hurd, P. L. (2005). Depression in men is associated with more
feminine ﬁnger length ratios. Personality and Individual Differences, 39, 829–836.
Becker, J. A., & Smenner, P. C. (1986). The spontaneous use of thank you by
preschoolers as a function of sex, socioeconomic status, and listener status.
Language in Society, 15, 537–545.
Bolier, L., Haverman, M., Kramer, J., Westerhof, G. J., Riper, H., Walburg, J. A., et al.
(2013). An internet-based intervention to promote mental ﬁtness for mildly
depressed adults: Randomized controlled trial. Journal of Medical Internet
Research, 15, e200.
Csathó, Á., Osváth, A., Bicsák, É., Karádi, K., Manning, J., & Kállai, J. (2003). Sex role
identity related to the ratio of second to fourth digit length in women. Biological
Psychology, 62, 147–156.
Emmons, R. A., & McCullough, M. E. (2003). Counting blessings versus burdens: An
experimental investigation of gratitude and subjective well-being in daily life.
Journal of Personality and Social Psychology, 84, 377–389.
Enders, C. K. (2001). A primer on maximum likelihood algorithms available for use
with missing data. Structural Equation Modeling, 8(1), 128–141.
Fink, B., Neave, N., Laughton, K., & Manning, J. T. (2006). Second to fourth digit ratio
and sensation seeking. Personality and Individual Differences, 41, 1253–1262.
Hayes, A. F. (2013). Introduction to mediation, moderation, and conditional process
analysis. New York, NY: Guilford.
Hönekopp, J. (2011). Relationships between digit ratio 2D:4D and self-reported
aggression and risk taking in an online study. Personality and Individual
Differences, 51, 77–80.
Hönekopp, J., Bartholdt, L., Beier, L., & Liebert, A. (2007). Second to fourth digit
length ratio (2D:4D) and adult sex hormone levels: New data and a meta-
analytic review. Psychoneuroendocrinology, 32, 313–321.
Hönekopp, J., & Thierfelder, C. (2009). Relationships between digit ratio (2D:4D) and
sex-typed play behavior in pre-school children. Personality and Individual
Differences, 47, 706–710.
Hönekopp, J., & Watson, S. (2010). Meta-analysis of digit ratio 2D:4D shows greater
sex difference in the right hand. American Journal of Human Biology, 22,
Hu, L. T., & Bentler, P. M. (1999). Cutoff criteria for ﬁt indexes in covariance structure
analysis: Conventional criteria versus new alternatives. Structural Equation
Modeling: A Multidisciplinary Journal, 6, 1–55.
Huffman, J. C., DuBois, C. M., Healy, B. C., Boehm, J. K., Kashdan, T. B., Celano, C. M.,
et al. (2014). Feasibility and utility of positive psychology exercises for suicidal
inpatients. General Hospital Psychiatry, 36(1), 88–94.
Kaczmarek, L. D., Goodman, F. R., Dra˛ _
zkowski, D., Kashdan, T. B., Połatyn
´ska, K., &
Komorek, J. (2014a). Instructional support decreases desirability and initiation
of a gratitude intervention. Personality and Individual Differences, 64, 89–93.
Kaczmarek, L. D., Kashdan, T., Dra˛ _
zkowski, D., Bujacz, A., & Goodman, F. (2014b).
Why do greater curiosity and fewer depressive symptoms predict gratitude
intervention use? Utility beliefs, social norm beliefs, and perceived self-control.
Personality and Individual Differences, 66, 165–170.
Kaczmarek, L. D., Kashdan, T. B., Dra˛ _
zkowski, D., Enko, J., Kosakowski, M., Szaefer, A.,
& Bujacz, A. (2015). Why do people prefer gratitude journaling over gratitude
letters? The inﬂuence of individual differences in motivation and personality on
web-based interventions. Personality and Individual Differences, 75, 1–6.
Kaczmarek, L. D., Kashdan, T. B., Kleiman, E., Ba˛ czkowski, B., Enko, B., Siebers, A.,
et al. (2013). Who self-initiates gratitude interventions in daily life? An
examination of intentions, curiosity, depressive symptoms, and life satisfaction.
Personality and Individual Differences, 55, 805–810.
Kashdan, T. B., Mishra, A., Breen, W. E., & Froh, J. J. (2009). Gender differences in
gratitude: Examining appraisals, narratives, the willingness to express
emotions, and changes in psychological needs. Journal of Personality, 77,
Killermann, S. (2013). The social justice advocate’s handbook: A guide to gender.
Austin, TX: Impetus Books.
Krause, N. (2006). Gratitude toward God, stress, and health in late life. Research on
Aging, 28, 163–183.
Krejtz, I., Nezlek, J. B., Michnicka, A., Holas, P., & Rusanowska, M. (in press). Counting
one’s blessings can reduce the impact of daily stress. Journal of Happiness
Lambert, N. M., & Fincham, F. D. (2011). Expressing gratitude to a partner leads to
more relationship maintenance behavior. Emotion, 11, 52–60.
Lyubomirsky, S., Dickerhoof, R., Boehm, J. K., & Sheldon, K. M. (2011). Becoming
happier takes both a will and a proper way: An experimental longitudinal
intervention to boost well-being. Emotion, 11, 391–402.
MacLusky, N. J., Bowlby, D. A., Brown, T. J., Peterson, R. E., & Hochberg, R. B. (1997).
Sex and the developing brain: Suppression of neuronal estrogen sensitivity by
developmental androgen exposure. Neurochemical Research, 22, 1395–1414.
Manning, J. T. (2011). Resolving the role of prenatal sex steroids in the development
of digit ratio. Proceedings of the National Academy of Sciences, 108–39,
Manning, J. T., Scutt, D., Wilson, J., & Lewis-Jones, D. I. (1998). The ratio of 2nd to 4th
digit length: A predictor of sperm numbers and concentrations of testosterone,
luteinizing hormone and oestrogen. Human Reproduction, 13, 3000–3004.
McCullough, M. E., Emmons, R. A., & Tsang, J. A. (2002). The grateful disposition: a
conceptual and empirical topography. Journal of personality and social
psychology, 82(1), 112.
McCullough, M. E., Kilpatrick, S. D., Emmons, R. A., & Larson, D. B. (2001). Is gratitude
a moral affect? Psychological Bulletin, 127, 249–266.
Meij, L., Almela, M., Buunk, A. P., Dubbs, S., & Salvador, A. (2012). 2D:4D in men is
related to aggressive dominance but not to sociable dominance. Aggressive
Behavior, 38, 208–212.
Muthén, L. K., & Muthén, B. O. (2012). Mplus user’s guide (7th ed.). Los Angeles, CA:
Muthén & Muthén.
Parks, A. C., Della Porta, M. D., Pierce, R. S., Zilca, R., & Lyubomirsky, S. (2012).
Pursuing happiness in everyday life: The characteristics and behaviors of online
happiness seekers. Emotion, 12(6), 1222–1234.
Proyer, R. T., Wellenzohn, S., Gander, F., & Ruch, W. (2014). Toward a better
understanding of what makes positive psychology interventions work:
Predicting happiness and depression from the Person intervention ﬁt in a
follow-up after 3.5 years. Applied Psychology: Health and Well-Being.
Schueller, S. M. (2010). Preferences for positive psychology exercises. The Journal of
Positive Psychology, 5, 192–203.
Schueller, S. M., & Parks, A. C. (2014). The science of self-help. European Psychologist,
Seligman, M. E., Rashid, T., & Parks, A. C. (2006). Positive psychotherapy. American
Psychologist, 61, 774.
Sin, N. L., & Lyubomirsky, S. (2009). Enhancing well-being and alleviating depressive
symptoms with positive psychology interventions: A practice friendly meta-
analysis. Journal of Clinical Psychology, 65, 467–487.
Smedley, K. D., McKain, K. J., & McKain, D. N. (2014). 2D:4D digit ratio predicts
depression severity for females but not for males. Personality and Individual
Differences, 70, 136–139.
Stenstrom, E., Saad, G., Nepomuceno, M. V., & Mendenhall, Z. (2011). Testosterone
and domain-speciﬁc risk: Digit ratios (2D:4D and rel2) as predictors of
recreational, ﬁnancial, and social risk-taking behaviors. Personality and
Individual Differences, 51, 412–416.
Tabachnick, B. G., & Fidell, L. S. (2007). Using multivariate statistics (5th ed.).
Needham Heights, MA, USA: Pearson Education.
Voracek, M., Pietschnig, J., Nader, I. W., & Stieger, S. (2011). Digit ratio (2D:4D) and
sex-role orientation: Further evidence and meta-analysis. Personality and
Individual Differences, 51, 417–422.
Yardley, L., Osmond, A., Hare, J., Wills, G., Weal, M., de Roure, D., et al. (2009).
Introduction to the LifeGuide: Software facilitating the development of
interactive behaviour change internet interventions. Paper presented at the
Proceedings of the AISB Convention, Edinburgh.
Yu, C. Y., & Muthén, B. (2002). Evaluation of model ﬁt indices for latent variable
models with categorical and continuous outcomes. Paper presented at the annual
meeting of the American Educational Research Association, New Orleans, LA.
Zheng, Z., & Cohn, M. J. (2011). Developmental basis of sexually dimorphic digit
ratios. Proceedings of the National Academy of Sciences, 108, 16289–16294.
M. Misiak et al. / Personality and Individual Differences 77 (2015) 68–73 73