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Prenatal exposure to sex hormones predicts gratitude intervention use. Examination of digit ratio, motivational beliefs, and online activities

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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 testosterone 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 facilitated by female sex and masculinity. These findings provide initial evidence for the biological grounding of individual differences in gratitude behavior.
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Prenatal exposure to sex hormones predicts gratitude intervention use.
Examination of digit ratio, motivational beliefs, and online activities
Michał Misiak
a,
, Lukasz D. Kaczmarek
a
, Todd B. Kashdan
b
, Marcin Zimny
a
, Hubert Urban
´ski
a
,
Adam Zasin
´ski
a
, David Disabato
b
a
Adam Mickiewicz University, Poland
b
George Mason University, United States
article info
Article history:
Received 25 October 2014
Received in revised form 20 December 2014
Accepted 22 December 2014
Keywords:
Gratitude
Hormones
Digit ratio
2D:4D
Sex differences
abstract
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
services.
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.
http://dx.doi.org/10.1016/j.paid.2014.12.041
0191-8869/Ó2015 Elsevier Ltd. All rights reserved.
Corresponding author at: Institute of Psychology, Adam Mickiewicz University
in Poznan
´, 89 Szamarzewskiego Street, PL-60-568 Poznan, Poland.
E-mail address: michalmis44@gmail.com (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,
2007).
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,
2011).
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
5.1. Participants
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
v
2
(50) = 49.32,
p> .05, and imputed with Expectation–Maximization method
(Enders, 2001). Written informed consent was obtained from each
participant.
5.2. Procedure
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.
5.3. Measures
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’’ (
a
= .83).
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’’ (
a
= .89).
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’’ (
a
= .92).
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’’ (
a
= .95).
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.
5.6. Results
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,
v
2
(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,
D
v
2
(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].
5.7. Discussion
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).
6.1. Participants
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%),
v
2
(104) = 124.79, p> .05, and imputed with
Expectation–Maximization algorithm (Enders, 2001).
6.2. Measures
Psychometrics: We used Study 1 measures for utility beliefs
(
a
= .86), social norm beliefs (
a
= .90), self-control beliefs
(
a
= .94), and behavioral intentions (
a
= .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
6.4. Results
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
well,
v
2
(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,
D
v
2
(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].
6.5. Discussion
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,
Table 1
Descriptive statistics and inter-correlations among Study 1 variables.
1234567
1. Utility beliefs
2. Social norm beliefs .48
**
3. Self-control beliefs .22
**
.09
4. Intention .47
**
.49
**
.19
**
5. Digit ratio .11 .08 .01 .11
6. Sex .15
*
.12 .02 .25
**
.04
7. Behavior first visit .11 .12 .05 .24
**
.06 .06
8. Behavior – last visit .06 .13
*
.08 .18
**
.10 .12
*
.51
**
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.
*
p< .05.
**
p< .01.
behavior
(last entry)
.92***
self-control
beliefs
digit ratio
.35***
.25***
.10*
sex
.13*.18***
-.14*
.16**
-.13
.38***
-.08
behavior
(first entry)
.05
.03 .40
.
2
7
.
85
intention
social norm
beliefs
utility beliefs
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
2
) is presented in the top right corner for each dependent variable.
p< .10,
p< .05,
⁄⁄
p< .01,
⁄⁄⁄
p< .001.
Table 2
Descriptive statistics and inter-correlations among Study 2 variables.
12345
1. Utility beliefs
2. Social norm beliefs .48
*
3. Self-control beliefs .29
*
.15
*
4. Intention .58
*
.42
*
.34
*
5. Digit ratio .12
*
.06 .02 .07
6. Sex .22
*
.10
*
.02 .19
*
.06
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.
*
p< .01.
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
health contexts.
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.
Ethical statement
The studies were conducted in accordance with guidelines pro-
vided by Institutional Ethics Committee.
self-control
beliefs
intention
utility beliefs
digit ratio
.15***
.46***
sex
.11** .07*
-.15***
.24***
-.07
.20***
.08
.02 .44
social norm
beliefs
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
2
) is presented in the top right corner for each dependent variable.
p< .10,
p< .05,
⁄⁄
p< .01,
⁄⁄⁄
p< .001.
72 M. Misiak et al. / Personality and Individual Differences 77 (2015) 68–73
Acknowledgements
The authors would like to thank Aleksandra Krajczewska, Syl-
wia Madej, Urszula Taczanowska, Weronika Sobczak, and Michał
Kosakowski for assisting with data collection.
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