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ORIGINAL PAPER
Confidence Mediates the Sex Difference in Mental Rotation
Performance
Zachary Estes •Sydney Felker
Received: 5 March 2011 /Revised: 29 September 2011 /Accepted: 1 October 2011 /Published online: 1 December 2011
Springer Science+Business Media, LLC 2011
Abstract On tasks that require the mental rotation of 3-
dimensional figures, males typically exhibit higher accuracy
than females.Using the most common measureof mental rota-
tion (i.e., the Mental Rotations Test), we investigated whether
individual variability in confidence mediates this sex differ-
ence in mental rotation performance. In each of four experi-
ments, the sex difference was reliably elicited and eliminated
by controlling or manipulating participants’ confidence. Specif-
ically, confidence predicted performance within and between
sexes (Experiment 1), rendering confidence irrelevant to the task
reliably eliminated the sex difference in performance (Experi-
ments 2 and 3), and manipulating confidence significantly
affected performance (Experiment 4). Thus, confidence medi-
ates the sex difference in mental rotation performance and hence
the sex difference appears to be a difference of performance
rather than ability. Results are discussed in relation to other
potential mediators and mechanisms, such as gender roles,
sex stereotypes, spatial experience, rotation strategies, work-
ing memory, and spatial attention.
Keywords Confidence Gender roles Mental rotation
Sex differences Spatial abilities Stereotype threat and lift
Introduction
Of all cognitive sex differences, the mental rotation of abstract
figures in 3-dimensional space is the most robust (Halpern, 2000;
Hines, 2004; Linn & Petersen, 1985; Maccoby & Jacklin, 1974).
Females typically respond less accurately and more slowly on
mental rotation tasks than do males (Lippa, Collaer, & Peters,
2010; Lohman, 1986;Mayloretal.,2007; Peters, 2005; Voyer,
Voyer, & Bryden, 1995), though the variability within each sex
is greater than the difference between sexes (Kail, Carter, &
Pellegrino, 1979;Resnick,1993). Meta-analyses indicate a
medium effect size of this sex difference in mental rotation
across age groups (Cohen’s d=.73, Linn & Petersen, 1985)
and among adults more specifically (d=.66, Voyer et al.,
1995). The single largest study of mental rotation (N=
255,100) also revealed a medium effect (d=.53, Peters,
Manning, & Reimers, 2007). Given the complexity of the task
and the magnitude of the sex difference, it likely has multi-
ple causes or mediators. Purely biological explanations (for
review, see Kimura, 1999) have received little empirical sup-
port, with no clear relationship between mental rotation abil-
ity and endogenous levels of sex hormones either prenatally
(Collaer & Hines, 1995; Hines et al., 2003; Rahman, Wilson, &
Abrahams, 2004) or in adulthood (Halari et al., 2005). More-
over, a biological constraint on mental rotation ability would not
preclude mediation of performance by sociocognitive factors
(e.g., Casey, 1996; Levine, Vasilyeva, Lourenco, Newcombe,
& Huttenlocher, 2005). Here, we examined whether one such
sociocognitive factor, namely participants’ confidence, contrib-
uted to this sex difference in mental rotation performance.
Although this presumed relation between confidence and men-
tal rotation performance has received little empirical attention,
related research on gender roles, sex stereotypes, and stereotype
threat provides a rich source of supportive evidence.
Z. Estes (&)
Department of Marketing, Bocconi University, Via Roentgen 1,
20136 Milan, Italy
e-mail: estes@unibocconi.it
S. Felker
Counseling and Psychiatric Services, University of Georgia Health
Center, Athens, GA, USA
123
Arch Sex Behav (2012) 41:557–570
DOI 10.1007/s10508-011-9875-5
Sex Stereotype Effects
Gender role beliefs and traits may partially explain the sex dif-
ference in mental rotation performance. Individuals who hold
traditional beliefs about gender roles and who engage in gender-
typical behaviors might believe in the common stereotype that
men are superior to women at spatial skills. This belief might
then induce or accentuate the sex difference in mental rotation
performance. Indeed, people are generally aware of the ste-
reotype that females have poorer spatial and mathematical abil-
ities than males and, in fact, nearly half of all females endorse
this stereotype to some extent (Blanton, Christie, & Dye, 2002).
Females perform better on a mental rotation task when asked to
imagine themselves as a stereotypical male than as a stereo-
typical female (d=.56, Ortner & Sieverding, 2008) and, more
generally, mental rotation ability is associated with more mas-
culine gender role traits (r=?.32) and less feminine gender role
traits (r=-.26, Saucier, McCreary, & Saxberg, 2002; see also
Signorella, Jamison, & Krupa, 1989). Performance on spatial
tasks thus is clearly related to gender role beliefs and traits.
Mental rotation performance may also be affected by mere
awareness of, rather than belief in, the stereotype that men are
superior to women on spatial tasks. Stereotype threat is the ten-
dency for members of a negatively stereotyped group to un-
derperform on tasks relevant to the stereotype (e.g., Steele,
1997;Steele&Aronson,1995; for review, see Maass & Cadinu,
2003; Schmader, Johns, & Forbes, 2008). In this case, the ste-
reotype that women have poor spatial skills could induce ste-
reotype threat in women, thereby accentuating any decrement in
mental rotation performance that may or may not occur other-
wise. McGlone and Aronson (2006) directly tested whether
stereotype threat affected mental rotation performance. Prior to
completing a mental rotation task, males and females at a private
university identified themselves via a series of questions. Some
participants answered questions about their gender. If stereo-
type threat affects mental rotation performance, then the sex
difference should be observed in this condition. Other partici-
pants answered questions about attending a private university.
This condition, which highlighted participants’ scholastic achieve-
ment, should attenuate the sex difference in mental rotation.
These predictions were supported. In fact, females performed
better when identified as a ‘‘private college student’’than when
identified as a female (d=1.38). Evidently, activating females’
achieved scholastic identity alleviated the stereotype threat and
allowed them to perform to their potential. In contrast, males
performed better when identified as a male than as a private
college studen t (d=.88). This result indicates a complemen-
tary effect, stereotype lift (Walton & Cohen, 2003), which is an
improvement in performance due to knowledge that an outgroup
is negatively stereotyped (see also Shih, Ambady, Richeson,
Fujita, & Gray, 2002; Shih, Pittinsky, & Ambady, 1999). In this
case, the stereotype that men are superior at spatial tasks may
bolster their confidence and subsequently improve their perfor-
mance.
Rather thanmanipulating participants’salient identity (e.g.,
McGlone & Aronson, 2006), Moe and Pazzaglia (2006)manip-
ulated the stereotype itself. They first had participants complete
a block of mental rotation trials, then they informed participants
either that men were better or that women were better at the task,
and finally they had those same participants complete another
block of mental rotation trials. Women performed significantly
worse after being told that men were better at the task (d=.44)
and significantly better after being told that women were better
(d=.35). Conversely, men performed significantly better after
being told that men were better at the task (d=.80) and sig-
nificantly worse after being told that women were better (d=
.78; see also Wraga, Duncan, Jacobs, Helt, & Church, 2006).
Massa, Mayer, and Bohon (2005) also manipulated the sex
stereotype, and additionally examined its interaction with gen-
der role beliefs. They found that women with masculine gender
role beliefs scored higher on a spatial task when they were told
that it measured spatial skills than when told that it measured
empathy (d=1.85), whereas women with feminine gender role
beliefs scored higher when told that it measured empathy than
when told that it measured spatial skills (d=1.31). Lippa et al.
(2010) examined mental rotation and line angle judgments
across 53 nations that varied in egalitarianism. Males outper-
formed females in every nation inbothmentalrotation(mean
d=.47) and line angle judgment (mean d=.49) and, somewhat
surprisingly, these sex differences were larger in highly egali-
tarian nations (e.g., Norway) than in less egalitarian nations
(e.g., Pakistan; mental rotation r=?.47; line angle r=?.41).
Lippa et al. attributed this finding to greater awareness of sex
stereotypes and/or greater susceptibility to stereotype threat in
egalitarian nations. So, in summary, beliefs about and aware-
ness of sex stereotypes are both related to the sex difference in
mental rotation performance. But how exactly might sex ste-
reotypes affect performance?
Confidence as a Potential Mediator
Much of the research on gender role and sex stereotype effects
assumes confidence as a potential cognitive mechanism by
which those social factors exert their effect. For instance, Steele
(1997) explained stereotype threat in terms such as self-regard,
self-efficacy, and self-confidence. Walton and Cohen (2003)
similarly explained stereotype lift thus: ‘‘By comparing them-
selves with a socially devalued group, people may experience an
elevation in their self-efficacy…[which] may be important to
maintaining confidence and motivation’’ (p. 456). The belief
that one (or one’s social group) is skilled or poor at a given task
may well affect one’s confidence when approaching that task
and this effect on confidence may have cascading effects on
558 Arch Sex Behav (2012) 41:557–570
123
basic cognitive skills, such as attention, memory, and judgment
(e.g., Schmader et al., 2008), which ultimately would affect
performance.
In their seminal study, Steele and Aronson (1995)demon-
strated that describing a difficult verbal test as diagnostic of
intellectual ability significantly increased self-doubt and
decreased performance among Black students but not among
White students. Stereotype threat also increased negative per-
formance-related thoughts among women, and these negative
thoughts mediated performance on a math test (Beilock, Rydell,
& McConnell, 2007; Cadinu, Maass, Rosabianca, & Kiesner,
2005; Schmader, Forbes, Zhang, & Mendes, 2009). And, con-
versely, women who self-affirmed another valued trait, such as
their creativity or humor, exhibited no stereotype threat effect on
a math test (Martens, Johns, Greenberg, & Schimel, 2006). Self-
doubt, negative thoughts, and self-affirmation are closely rela-
ted to the more general construct of confidence. Thus, sex ste-
reotypes are widely thought to affect performance on cognitive
tasks indirectly, partially by influencing participants’ con-
fidence. We therefore tested whether confidence mediated
mental rotation performance.
Preliminary evidence suggests that confidence might indeed
underlie the sex difference in mental rotation. Females reported
less confidence than males on cognitive tasks in general (Beyer
& Bowden, 1997; Maccoby & Jacklin, 1974) and on mental
rotation tasks in particular (d=1.04, Cooke-Simpson & Voyer,
2007; see also Pallier, 2003). Moreover, because confidence is
gauged before the judgment is made (Baranski & Petrusic,
1998), it may affect that judgment (Petrusic & Baranski, 2003).
Indeed, confidence has been shown to predict performance on
other cognitive tasks, such as mathematical problem solving
(Casey, Nuttall, & Pezaris, 1997;Schmaderetal.,2009)and
semantic categorization (Estes, 2004; Pasterski, Zwierzynska,
&Estes,2011). So given these sex differences in confidence
and mental rotation, and given that confidence mediates per-
formance on some cognitive tasks, confidence might mediate
the sex difference in mental rotation. This presumed relation
between confidence and spatial abilities, however, has not been
thoroughly explored and the results are mixed. Gonzales, Blan-
ton, and Williams (2002) found that participants’ self-evaluations
of task competence did not predict their scores on a test of
mathematical and spatial abilities. In contrast, Cooke-Simpson
and Voyer (2007) found that participants’ confidence ratings
reliably predicted their mental rotation scores (r=?.69), with
more confident men and women outperforming their less con-
fident peers.
The most common measure of mental rotation performance
is the Mental Rotations Test (MRT; Vandenberg & Kuse, 1978),
which is based on the 3-dimensional block figures introduced by
Shepard and Metzler (1971) and updated by Peters et al. (1995).
Each trial of the MRT consists of one standard and four alter-
native figures. Exactly two of the alternatives are rotated ver-
sions of the standard; the other two are non-matching distracters
(see Fig. 1). Thus, each trial has two correct answers. Critically,
though, participants may omit one or both responses. Females
tend to provide fewer responses than males (d=.30, Voyer,
Rodgers, & McCormick, 2004; see also Voyer & Saunders,
2004), but statistically correcting for differential response rates
does not eliminate the sex difference in performance (Masters,
1998;Peters,2005; Peters et al., 1995; Resnick, 1993). Never-
theless, the mere possibility of omitting responses supports the
hypothesis that confidence mediates the sex difference in
accuracy on the MRT. The decision to respond or abstain on any
given trial of the MRT is presumably based on one’s confidence
in knowing the correct response. Because confidence appears to
be an important component of the MRT, it stands as a plausible
mediator of performance.
The present study therefore investigated whether confidence
mediated accuracy on this most common and robust measure of
mental rotation performance. Specifically, if confidence medi-
ates mental rotation, then (1) confidence should predict mental
rotation scores not only between sexes, but also within sexes, (2)
rendering confidence irrelevant to the task should attenuate the
sex difference, and (3) manipulating participants’ confidence
should affect their mental rotation performance. We tested these
three predictions across four experiments.
Experiment 1
In Experiment 1, we tested whether confidence predicted men-
tal rotation performance between sexes, within each sex, and
within individuals. Participants completed a standard MRT, but
they additionally rated their confidence in each response. Fol-
lowing common procedure, the MRT was administered under a
time constraint of 15 s per trial, which allows greater experi-
mental control without influencing the magnitude of the sex dif-
ference (Peters, 2005; Voyer et al., 2004).
Fig. 1 A trial of the MRT
Arch Sex Behav (2012) 41:557–570 559
123
Cooke-Simpson and Voyer (2007) provided tentative evi-
dence that confidence predicted MRT performance, but that
study had several critical limitations. As described above, each
item on the MRT includes four alternative figures, exactly two
of which are rotated versions of the standard. Participants in
Cooke-Simpson and Voyer’s study only rated their confidence
in each item, which included between zero and two responses
(depending on how many responses the participant omits on a
given item). Unfortunately, this methodology likely decreased
the accuracy of participants’ confidence ratings. That is, because
participants provided confidence ratings for each pair of
responses, participants must not only gauge their confidence but
also choose a decision rule and apply the chosen computation to
determine their confidence rating. Should the confidence rating
be an average over the two responses, should it be the minimum
of the two or should it be the maximum? Conversely, this
methodology also limits the precision of possible conclusions
from the research: Because participants provided a single con-
fidence rating for each pair of responses, it is unclear to which
response a given rating refers. Finally, Cooke-Simpson and
Voyer examined the relation between confidence and perfor-
mance only across individuals. That is, they calculated each
participant’s mean confidence rating and overall accuracy
score, and they tested whether highly confident individuals out-
performed less confident individuals. While such an analysis is
informative, it fails to test the potential relation between con-
fidence and performance within an individual.
1
Is a given par-
ticipant more likely to respond correctly when she is highly con-
fident than when she is less confident?
To address these limitations, in Experiment 1, we required
participants to rate their confidence after each individual response
(rather than after each pair of responses). By removing the
complexity and ambiguity of judging confidence over multiple
responses, this procedure may elicit more accurate ratings and
more precise conclusions. Furthermore, in addition to examining
the relation between confidence and performance across individ-
uals, Experiment 1 also examined this relation within individuals.
This allowed us to investigate not only whether highly confident
individuals tend to outperform less confident individuals (as in
Cooke-Simpson & Voyer, 2007), but also whether a given partici-
pant was more likely to respond correctly when she was highly
confident than when she was less confident. That is, we examined
the relation between confidence and performance on a trial-by-
trial basis. If confidence mediates mental rotation performance,
then confidence ought to predict accuracy on the MRT across
sexes, within each sex, and possibly even within individuals.
Method
Participants
All participants in each of the experiments reported herein were
undergraduates at a large North American university, most were
between the ages of 17 and 23 years, all received partial course
credit for participation, and none participated in more than one
of the experiments. Seventy undergraduates (35 females, 35
males) participated in Experiment 1.
Measure
The 24-item version of the MRT was used. Following standard
procedures for administration of the MRT, participants were
informed that each standard figure had two matching alterna-
tives, and they were instructed not to respond unless they were
sure of the answer (see Voyer & Saunders, 2004).
Procedure
In each of the present experiments, participants were tested
individually in a sound attenuated room and the entire experi-
ment (including the instructions) was administered via com-
puter. Each trial of Experiment 1 began with presentation of the
standard and four alternatives aligned horizontally onscreen
(see Fig. 1). The figures remained onscreen for 15 s and were
then replaced with the prompt ‘‘Please enter your first choice.’’
Participants either pressed the A, B, C or D key or else pressed
the spacebar if they were unsure of the answer. Participants were
then asked‘‘How confident are you in this choice?’’The numbers
1 (‘‘n o t a t a ll’’) th r o u g h 7 (‘‘ext r e m ely ’’) w e r e t he onl y v a l id
choices. The prompt ‘‘Please enter your second choice’’ then
appeared, followed again by ‘‘How confident are you in this
choice?’’ On trials where the participant omitted a response (by
pressing the spacebar), they were instructed to press any num-
ber for the confidence rating and those ratings were excluded
from all analyses. After the second confidence rating had been
entered, there was a 1 s inter-trial interval prior to presentation of
the next set of figures. Four practice trials preceded the 24 exper-
imental trials, which were presented in random order. After
completion of all experimental trials, participants were promp-
ted to press the M key or the F key to indicate that they were male
1
Cooke-Simpson and Voyer (2007) also computed two additional mea-
sures of the relation between confidence and accuracy (i.e., Brier scores and
‘‘confidence relative to performance’’), but again their analyses were at the
level of the individual rather than the individual response. That is, for each
participant they calculated the mean confidence and the mean accuracy,
collapsed across trials, and then they compared the group means. They did
not examine the relation between confidence and accuracy on each trial.
Moreover, both of their additional measures required the assumption that
confidence ratings on a 1-to-7 scale map directly and evenly onto a prob-
ability scale. For instance, those measures assumed that a confidence rating
of 1 indicated a probability judgment of 0. This assumption is questionable.
Presumably, if a participant believes that there is zero chance that his
response is correct, then he would either omit that responseor else change it
to a different response. The important point for our purposes here is that
Cooke-Simpson and Voyer did not examine the relation between confi-
dence and accuracy on a trial-by-trial basis, as we did in Experiment 1.
560 Arch Sex Behav (2012) 41:557–570
123
or female, respectively, and then to enter their age into a text-
box.
Analyses
Foreachoftheexperiments,weadopted the relatively strict
criterion that any participant who was more than 2.5 SD beyond
the group mean for any of the measures was considered an out-
lier and was, therefore, excluded from analyses. In the present
experiment, this led to the exclusion of three males.
Accuracy was defined as the total percent correct (i.e.,
number correct/number possible). Scores were also corrected
for individual differences in response rate by excluding omitted
trials (i.e., number correct/number responses). Corrected scores
were highly correlated with total scores, r(67) =?.86, p\.001.
Some researchers score a trial as correct only if two correct
responses are provided. These scores were also highly corre-
lated with the total scores, r(67) =?.97, p\.001. Given these
high intercorrelations (see also Masters, 1998; Resnick, 1993;
Voyer et al., 1995) and for the sake of simplicity, hereafter we
report only the total percent correct.
Results and Discussion
As expected, an independent samples t-test revealed that males
(M=5.61, SD =1.02) were more confident than females (M=
4.62, SD =1.41), d=.74, t(65) =3.26, p\.01. The effect size
of this sex difference in confidence was comparable to that
observed in prior research (d=1.04; Cooke-Simpson & Voyer,
2007).AsshowninTable1, males were also significantly more
accurate than females, t(65) =2.44, p\.05, and the effect size
(d=.58) was comparable to that observed in other studies (d=
.66, Voyer et al., 1995). Males (M=6, SD =8) and females
(M=8, SD =8) did not differ significantly in the percentage of
responses omitted, t(65) =1.10.
As illustrated in Fig. 2, confidence predicted accuracy across
both sexes, r(67) =?.56, p\.001, and the strength of this
correlation was comparable to that observed in prior studies
(r=?.69; Cooke-Simpson & Voyer, 2007). Confidence also
predicted accuracy among females, r(35) =?.45, p\.01, and
males r(32) =?.62, p\.001. The slope of this relationship did
not differ between males and females, z=.94. This suggests that
confidence may contribute not only to the sex difference in
mental rotation performance, but also to individual differences
within each sex (see also Cooke-Simpson & Voyer, 2007).
Confidence was unrelated to the percentage of omitted trials,
r=-.14. Rather, omissions were negatively correlated with
accuracy, r(67) =-.47, p\.001; the fewer responses a partic-
ipant provided, the lower the overall score.
Figure 2illustrates the relationship of confidence and accu-
racy across participants; individuals who were highly confident
also tended to be highly accurate. Figure 3illustrates the rela-
tionship of confidence and accuracy within participants. That is,
for each participant, we calculated the accuracy at each point on
the confidence scale (i.e., 1–7).Be cause most participants used a
restricted range of confidence ratings, and because the ratings
were not uniformly distributed across the scale, there were
unequal numbers of observations across the confidence points.
Despite this limitation, a linearly increasing function was
observed between confidence and accuracy for both males and
females. That is, as one’s confidence increased, so did one’s
accuracy (see Fig. 3). This result indicates that participants were
successful at gauging their own relative performance on indi-
vidual trials of the MRT. So, together, Figs. 2and 3reveal that
males and females were similarly successful at calibrating their
confidence to their accuracy (Fig. 3), though males tended
toward the upper part of the distribution on both confidence and
accuracy (Fig. 2).
These analyses establish a relationship among sex, confi-
dence, and accuracy. However, they do not discriminate between
alternative models of mediation. The question of interest is
whether confidence mediated the effect of sex on accuracy, as
Table 1 Accuracy (% correct) as a function of sex (Experiments 1–4)
Experiment Condition Females Males d
NMSDNMSD
1 Omission 35 68 12 32 75 12 .58*
2 Omission 41 63 12 43 73 14 .72**
Commission 42 73 12 43 75 12 .19
3 Commission 39 80 13 39 80 15 .03
Confidence 35 75 17 30 93 6 1.16***
4 High confidence 35 81 13 35 90 11 .74**
Low confidence 35 77 15 34 85 16 .45
deffect size (Cohen’s d) of the sex difference in accuracy. Participants
were given 15 s per trial in Experiments 1, 2 and 4, and were given
unlimited time in Experiment 3
p\.06; * p\.05; ** p\.01; *** p\.001
0
10
20
30
40
50
60
70
80
90
100
1234567
Confidence
Accuracy (% Correct)
Males Fe males
Fig. 2 Accuracy as a function of confidence across participants, Exper-
iment 1
Arch Sex Behav (2012) 41:557–570 561
123
we hypothesized, or whether accuracy mediated the effect of sex
on confidence. We tested these alternative models via Baron and
Kenny’s (1986) regression method for simple mediation. The
mediation model is illustrated in Fig. 4. For these regressions,
the sex factor was coded as 1 for male and 2 for female, so that
negative coefficients indicate lower scores for females. As estab-
lished above, sex negatively predicted both confidence ratings,
b=-.38, and mental rotation scores, b=-.29, whereas con-
fidence positively predicted mental rotation scores, b=?.56.
Most critically, when sex and confidence were both included as
predictor variables in the same regression, confidence remained
a strong positive predictor of mental rotation, b=?.53, t(65) =
4.73, p\.001, whereas sex failed to predict mental rotation
scores, b=-.09, t(65)\1. Stated differently, when the effect of
confidence was taken into account, the sex difference in mental
rotation scores was eliminated. That confidence reduced the
predictive validity of the sex factor to nearly zero (i.e., b=
-.09) indicates not only that confidence mediated the sex dif-
ference in mental rotation performance, but indeed that this
mediation was nearly complete. Finally, a reverse mediation
analysis tested the alternative model that mental rotation scores
mediated the effect of sex on confidence. With sex and mental
rotation scores as the predictor variables and confidence as
the criterion, sex significantly predicted confidence, b=-.23,
t(65) =2.23, p\.05. Thus, mental rotation performance did not
mediate the sex difference in confidence, but rather confidence
strongly mediated the sex difference in mental rotation per-
formance.
In conclusion, Experiment 1 corroborated the finding that
confidence predicted mental rotation performance both across
and within sexes (Cooke-Simpson & Voyer, 2007). Experiment
1 further demonstrated, for the first time, that confidence pre-
dicted mental rotation performance within individuals: Partic-
ipants were more accurate on trials for which they were more
confident. These results thus provide the most precise evidence
to date of the relation between confidence and mental rotation.
Finally, Experiment 1 also provided the first evidence of the
direction of this relationship: Mediation analyses revealed that
confidence mediated the sex difference in mental rotation per-
formance whereas mental rotation performance did not mediate
the sex difference in confidence. Nonetheless, such mediation
analyses provide only indirect evidence of the nature of this
relationship. Experimental manipulations of confidence would
provide more direct evidence of its relation to mental rotation
performance. Experiments 2–4 thus manipulated confidence
and examined its influence on mental rotation performance.
Experiment 2
In Experiment 2, we sought to attenuate the sex difference in
mental rotation performance by rendering confidence irrelevant
to the task. One group of participants completed the standard
MRT, in which they were permitted to omit trials at their dis-
cretion (‘‘omission’’ group). This condition was identical to the
preceding experiment, except that confidence ratings were not
collected. Another group of participants also completed the
MRT, but were required to respond on every trial (‘‘commis-
sion’’ group). Our rationale was that when participants may omit
trials, then one’s confidence on each trial determines whether to
respond (commit) or abstain (omit), and hence confidence is
highly relevant to the task. This omission group should therefore
replicate the sex difference in mental rotation that was observed
in Experiment 1 and elsewhere. In contrast, when omissions are
not permitted, the efficacy of evaluating one’s confidence is
eliminated, and hence we hypothesized that confidence would
have a diminished effect on performance. So if indeed confi-
dence contributes to the sex difference in mental rotation, then
requiring a response on every trial should attenuate that differ-
ence by rendering confidence irrelevant to the task.
Alternatively, requiring participants to respond on every trial
could conceivably render participants’ confidence even more
salient, in which case this commission group might exhibit an
even larger sex difference in mental rotation than that observed
in the omission group. Thus, if confidence affects mental rota-
tion, then we should observe an interaction such that the omis-
sion group should exhibit a sex difference that is either larger or
smaller than that of the commission group. Critically, an inter-
action in either direction would suggest that confidence
0
10
20
30
40
50
60
70
80
90
100
12345 67
Confidence
Accuracy (% Correct)
Males Females
Fig. 3 Accuracy as a function of confidence within participants,
Experiment 1
Sex Mental Rotation
Mental Rotation
Confidence
Sex
β
= -.29*
β
= -.38**
β
= +.53***
β
= -.09 ns
Fig. 4 Confidence as a mediator of the sex difference in mental rotation
performance, Experiment 1. *p\.05; **p\.01; ***p\.001
562 Arch Sex Behav (2012) 41:557–570
123
mediates mental rotation. If confidence was unrelated to mental
rotation, then the sex difference should be equivalent across
groups (i.e., no interaction should occur).
Method
A total of 174 undergraduates (85 females, 89 males) partici-
pated. Three outlying males and two outlying females were
excluded from all analyses on the basis of the criteria established
above. Materials were identical to those of Experiment 1. For
participants in the omission group, the procedure was identical
to that of Experiment 1, with the exception that confidence rat-
ings were not collected. The procedure of the commission con-
dition was identical to the omission condition, except that par-
ticipants were instructed to provide two responses on each trial.
They were instructed to provide their best guess if they were
unsure of an answer.
Results and Discussion
Results are summarized in Table 1. The sex difference in accu-
racy was replicated in the omission condition but not in the com-
mission condition. A 2 (Sex) by 2 (Condition) analysis of var-
iance (ANOVA) confirmed a significant interaction in accuracy,
F(1, 165) =4.19, p\.05. That is, in the omission group, males
significantly outperformed females, t(82) =3.54, p\.01. The
effect size (d=.72) was comparable to other studies that have
used this standard ‘‘omission’’ instruction with the MRT (d=
.66; Voyer et al., 1995). In contrast, males and females in the
commission group did not differ in accuracy, t(83)\1. To
examine the reliability of this null sex difference in the com-
mission group, we conducted post hoc power analyses (see Faul,
Erdfelder, Lang, & Buchner, 2007). In their meta-analysis of 42
published studies of the sex difference on the MRT among
participants over 18 years of age, Voyer et al. (1995,Table4)
found an effect size of d=.66. In Experiment 1 and in the omis-
sion group of Experiment 2, we obtained similar effect sizes of
.58 and .72, respectively (see Table 1). We therefore adopted .66
as our estimate of effect size. Using the standard alpha of .05, the
achieved power in the commission group was .92, where power
of .80 or higher is typically considered good. Thus, despite good
statistical power to detect a sex difference on the MRT, no such
difference was observed in the commission group.
We suggest that the mere possibility of omitting a response
renders confidence efficacious, because presumably the deci-
sion to respond or omit was based on confidence. But when
required to respond, confidence was no longer efficacious and
hence its effect was attenuated. However, females (M=14%,
SD =12) also omitted more responses than males (M=7%,
SD =7), d=.63, t(82) =3.04, p\.01, and this effect size was
somewhat larger than that observed in prior research (d=.30,
Voyer et al., 2004). The sex difference in accuracy thus could
be attributable to omissions rather than confidence per se. We
therefore held omissions constant via analysis of covariance,
and the sex difference in accuracy remained significant, F(1,
81) =4.86, p\.05. Thus, the sex difference in mental rotation
was attributable to confidence rather than omissions.
Experiment 3
Experiment 3 provided a further test of whether the sex difference
in performance is better explained by confidence or by omissions.
One group of participants replicated the commission condition of
Experiment 2 (‘‘commission’’ group). Another group was also
required to respond on every trial but, critically, they also pro-
vided confidence ratings on each trial (‘‘confidence’’group). If the
sex difference in performance is due to omissions, then neither
group should exhibit a sex difference, because both groups were
disallowed from omitting responses. Alternatively, if the sex
difference is due to confidence, then only the confidence group
should exhibit a sex difference, because confidence is irrelevant
to the commission group. To generalize the results across timing
conditions, participants were given unlimited time to complete
each trial (see Lohman, 1986;Masters,1998;Peters, 2005; Voyer
et al., 2004).
Method
A total of 148 undergraduates (76 females, 72 males) partici-
pated. Three outlying males and two outlying females were
excluded from all analyses on the basis of the criteria established
above. Materials were identical to those of Experiment 1. For
participants in the commission group, the procedure was iden-
tical to the commission condition of Experiment 2, except that
participants were given unlimited time to complete each trial.
Thus, the stimuli remained onscreen until the participant pro-
vided two responses. The procedure of the confidence condition
was identical, except that confidence ratings were also collected
after each response, as in Experiment 1.
Results and Discussion
Results are summarized in Table 1. Relative to Experiment 2,
the unlimited time allowed on each trial in Experiment 3 appears
to have increased accuracy (see also Peters, 2005). But, most
importantly, the confidence group replicated the sex difference
in accuracy that was obtained in Experiment 1 whereas the
commission group replicated the null sex difference that was
obtained in Experiment 2. A 2 (Sex) by 2 (Condition) ANOVA
confirmed a significant interaction in accuracy, F(1, 139) =
15.94, p\.001. That is, males and females in the commission
group did not differ in accuracy, t(76)\1, despite good statis-
tical power to detect such a difference (with d=.66 and a=.05,
power =.89). In the confidence group, however, males were
Arch Sex Behav (2012) 41:557–570 563
123
significantly more accurate than females, t(63) =5.72, p\.001.
This sex difference was large (d=1.16), but within the normally
observed range of effect sizes on this task (Voyer et al., 1995).
Males (M=6.35, SD =.63) were also more confident than
females (M=5.19, SD =1.19), d=1.04, t(63) =4.84, p\
.001, and the effect size was comparable to that observed in prior
studies (d=1.04, Cooke-Simpson & Voyer, 2007). Thus, when
confidence was irrelevant to the task (i.e., commission group),
the sex difference in accuracy was eliminated. But when con-
fidence was reinstated as relevant to the task (i.e., confidence
group), the sex difference in accuracy re-emerged. Experiment
3 therefore supported the hypothesis that mental rotation is
mediated by confidence.
In fact, as illustrated in Fig. 5, confidence ratings predicted
accuracy across sexes, r(65) =?.70, p\.001; individuals who
were highly confident were also highly accurate. The stren gth of
this correlation was comparable to that observed in prior studies
(r=?.69, Cooke-Simpson & Voyer, 2007). The correlation
was also significant among females, r(35) =?.63, p\.001, but
not among males, r=?.23, and these slopes differed signifi-
cantly, z=1.94, p=.05. This differential relation between con-
fidence and accuracy might indicate that, under these circum-
stances, females gauged their own relative performance more
accurately than males did. However, no difference in cali-
bration was observed in Experiment 1. The lack of correlation
among males in the present study is more likely attributable
to h ighly restricted ranges of both confidence and accurac y (see
Fig. 5). Indeed, relative to Experiment 1, both the confidence
and the accuracy of both males and females increased substan-
tially. This systematic increase was most likely due to the unlim-
ited time allowed for responding in Experiment 3, compared to
15 s per trial in Experiment 1. As in Experiment 1, we addi-
tionally examined the relationship of confidence and accuracy
withi n participants. For both males and females, accuracy was a
linearly increasing function of confidence (see Fig. 6). This
result replicates the general pattern observed in Experiment 1
(Fig. 3), and indicates that both males’ and females’ confi-
dence was indeed calibrated to their performance.
Experiment 4
In Experiment 4, we manipulated participants’ confidence prior
to administration of the MRT. All participants first completed a
line judgment task that was intentionally difficult, so that par-
ticipants would be unable to gauge their performance. On each
trial of this task, one line was presented in a vertical orientation
and another line was presented horizontally. The task was to
judge whether the two lines were of the same length. As
expected, performance on this task was near chance (M=.56,
SE =.01), with males and females performing equally poorly,
t(137)\1.
Upon completion of the line judgment task, participants were
randomly informed that their performance on the line judgment
task was either above average (‘‘high confidence’’ condition) or
below average (‘‘low confidence’’ condition). All participants
then immediately completed the standard (omission) version of
the MRT, with 15 s per trial. Because the line judgment task
required comparison of lines at different orientations, we
assumed that participants would interpret the evaluation of their
performance on this task as relevant to the subsequent MRT. If
confidence mediates mental rotation performance, then partic-
ipants in the high confidence condition should outperform their
counterparts in the low confidence condition.
Method
Participants
A total of 153 undergraduates (76 females, 77 males) partici-
pated. Eight outlying males and six outlying females were
0
10
20
30
40
50
60
70
80
90
100
12345 67
Confidence
Accuracy (% Correct)
Males Fe males
Fig. 5 Accuracy as a function of confidence across participants, Exper-
iment 3
0
10
20
30
40
50
60
70
80
90
100
123 4567
Confidence
Accuracy (% Correct)
Males Females
Fig. 6 Accuracy as a function of confidence within participants, Exper-
iment 3
564 Arch Sex Behav (2012) 41:557–570
123
excluded from all analyses on the basis of the criteria estab-
lished above.
Measures
The line judgment task consisted of three standard lines and
five alternative lines for each standard. The ‘‘large’’ standard
was 4.5 in., the ‘‘medium’’ was 33% shorter (3.02 in.), and the
‘‘small’’ was 67% shorter than the‘‘large’’ (1.49 in.). For each
of the three standards, one alternative was identical, one was
10% shorter, one was 5% shorter, one was 5% longer, and one
was 10% longer. Materials ofthe MRT were identical to those
of Experiment 1.
Procedure
Participants were initially informed that the experiment would
consist of two parts and that the first part was a line judgment
task. On each trial of the line judgment task, the standard was
presented in vertical orientation. The alternative always
appeared in horizontal orientation at the midpoint of the stan-
dard, separated horizontally by 1 in. Each standard was
presented eight times. On four of those presentations, the
alternative was of the same length. On the other four presenta-
tions, the alternative was of a different length (i.e., 10% shorter,
5% shorter, 5% longer, or 10% longer). The lines were presented
in the upper half of the computer display. After 2 s, the prompt
‘‘Same (S) or different (D)?’’appeared in the lower part of the
display while the lines remained onscreen. Participants indi-
cated by keypress whether the lines were of the same length.
Participants were randomly assigned to either a high confi-
dence or a low confidence condition. At the conclusion of the
line judgment task, the following statement was presented in the
upper part of the display for 3 s: ‘‘EVALUATION: Your per-
formance indicates that you are…’’ After 3 s, participants in the
high confidence condition saw ‘‘ABOVE AVERAGE’’ in the
middle of the display whereas participants in the low confidence
condition saw ‘‘BELOW AVERAGE.’’ After a 1 s delay, ‘‘on
the line judgment task’’ appeared in the lower part of the screen.
The entire statement of evaluation remained onscreen simulta-
neously for three additional seconds. Finally, the prompt‘‘Please
press the spacebar to proceed to the second part of the experi-
ment’’ appeared near the bottom of the display. The procedure of
the MRT was identical to that of the omission condition of
Experiment 2.
Results and Discussion
Results are summarized in Table 1. A 2 (Sex) by 2 (Condition)
ANOVA confirmed an overall sex difference in accuracy, F(1,
135) =12.59, p\.001, with males again outperforming females.
The effect sizes in the low and high confidence conditions were
comparable to those observed in prior studies (d=.66, Voyer
et al., 1995). The interaction was not significant, F(1, 135)\1.
Most critically, there was a significant main effect of condition on
accuracy, F(1, 135) =3.79, p=.05, with participants in the high
confidence group significantly outperforming those in the low
confidence group. That is, manipulating participants’ confidence
affected their mental rotation: Participants scored higher on the
MRT after being randomly informed that they were above aver-
age on a line judgment task than after being informed that they
were below average on the line judgment task. Notably, females
in the high confidence group and males in the low confidence
group did not differ in accuracy, t(68) =1.09, despite good sta-
tistical power to detect such a difference (with d=.66 and
a=.05, power =.86).
A 2 (Sex) by 2 (Condition) ANOVA on the percentage of
omitted responses yielded no main effect of condition, F(1,
135)\1, and no interaction, F(1, 135)\1, indicating that the
effect of condition on accuracy was not attributable to a dif-
ference in omissions between conditions. However, as in Exper-
iment 2, there was an overall sex difference in omissions, F(1,
135) =16.74, p\.001. Females (M=5, SD =6) again omitted
more responses than males (M=1, SD =2), and the effect size
(d=.66) was comparable to that observed in Experiment 2
(d=.63) and in other studies (d=.30, Voyer et al., 2004). We
therefore held omissions constant via analysis of covariance, as
in Experiment 2, and the sex difference in accuracy remained
significant, F(1, 134) =4.36, p\.05. Thus, the sex difference
in mental rotation was attributable to confidence rather than
omissions.
General Discussion
Given that men are more confident than women on mental
rotation tasks (Cooke-Simpson & Voyer, 2007) and that con-
fidence mediates performance on other cognitive tasks (Casey
et al., 1997; Estes, 2004), we hypothesized that confidence
would mediate the sex difference in mental rotation perfor-
mance. This hypothesis seemed plausible for two reasons. First,
it is consistent with much prior research demonstrating that
sociocognitive factors, such as gender role beliefs (e.g., Massa
et al., 2005), sex-typedness (e.g., Saucier et al., 2002), sexual
orientation (e.g., Peters et al., 2007), and salience of sex ste-
reotypes (e.g., McGlone & Aronson, 2006), are related to
mental rotation performance. Confidence may serve as a com-
mon mediator by which these distal factors affect mental rota-
tion. Second, because one is allowed to omit responding on any
given trial of the MRT, one’s choice to respond or abstain pre-
sumably derives from one’s confidence in knowing the correct
response. Hence, confidence is efficacious in that it determines
whether to respond or abstain. So confidence is relevant to
mental rotation performance and because confidence can affect
Arch Sex Behav (2012) 41:557–570 565
123
performance on cognitive tasks (Petrusic & Baranski, 2003), it
was a plausible mediator.
Experiment1replicatedthesexdifference in mental rotation
performance, but also showed that confidence mediated this sex
difference and taking confidence into account eliminated the sex
difference in mental rotation scores. Confidence predicted per-
formance between sexes, within each sex, and even within indi-
viduals. The commission condition of Experiment 2 removed the
efficacy of confidence by requiring participants to respond on
every trial. When confidence was thus rendered irrelevant, the sex
difference in accuracy that was observed in the standard omission
condition was eliminated in this commission condition. In Exper-
iment 3, the commission condition once again eliminated the sex
difference in accuracy. However, the confidence condition rein-
stated the relevance of confidence by additionally requiring par-
ticipants to judge their confidence in each response. With con-
fidence thus emphasized, the sex difference in accuracy re-
emerged. Finally, in Experiment 4, we manipulated partici-
pants’ confidence by randomly informing them that they were
either above or below average on an extremely difficult line
judgment task. Participants subsequently performed better
and worse, respectively, on the MRT. Moreover, women in the
high confidence condition performed as well on the MRT as
men in the low confidence condition. Thus, in each of the four
experiments, we replicated and eliminated the sex difference in
mental rotation performance by controlling or manipulating
participants’ confidence.
Understanding the source(s) of the sex difference ultimately
may facilitate the bridging of the gender gap in mental rotation
skills. Most directly, boosting females’ confidence in their men-
tal rotation abilities appears to improve their actual performance
(see also Moe & Pazzaglia, 2006;Wragaetal.,2006). Poten-
tially effective methods for achieving this outcome include
rejecting the negative stereotype that women have poor spatial
skills, encouraging women to view spatial skills as learnable,
encouraging females to engage in more spatial tasks, and pro-
viding positive feedback when they do so. Such methods have
proven effective for combating the effects of negative ste-
reotypes on spatial tests and other performance measures (e.g.,
Aronson, Fried, & Good, 2002; Feng, Spence, & Pratt, 2007;
Johns, Schmader, & Martens, 2005; Martens et al., 2006;Moe,
Meneghetti, & Cadinu, 2009). Another promising method is
to encourage women to reappraise the arousal they experience
when performing under stereotype threat (Jamieson, Mendes,
Blackstock, & Schmader, 2010; Johns, Inzlicht, & Schmader,
2008;Schmaderetal.,2009). The present resea rch suggests that
merely rendering confidence irrelevant to the task might also
improve females’ mental rotation performance.
A corollary implication of this research is that the MRT may
accentuate the sex difference in performance. Because partici-
pants may omit responses, the MRT implicitly induces par-
ticipants to evaluate their confidence on each trial, thereby
affecting performance. Thus, it is no coincidence that the MRT
exhibits the largest and most robust cognitive sex difference,
with effect sizes (Cohen’s d)rangingfrom.45to1.16inthe
present study (see Table 1) and an average effect size of .66
across studies (Voyer et al., 1995). The large magnitude of this
sex difference may be a direct consequence of the fact that
confidence is particularly efficacious for performance on the
MRT. This is not to say that the sex difference is merely a
methodological artifact; rather, it may explain why the magni-
tude of the sex difference varies across different tests of mental
rotation (see Voyer et al., 1995). This raises the question of
whether confidence also mediates the sex difference observed
on other tests of mental rotation (e.g., the Spatial Relations sub-
test of the Primary Mental Abilities test) (Thurstone & Thur-
stone, 1949) and spatial abilities more generally (e.g., the Rod-
and-Frame test) (Witkin & Asch, 1948). Thus, the full impli-
cations of this research for the general class of sex differences in
spatial ability are yet to be determined.
The large magnitude of the sex difference in mental rotation
suggests that it may well have multiple causes. Moreover, those
causes may be described at multiple levels of analysis, from dis-
tal factors (i.e., mediators) such as gender role beliefs to prox-
imal factors (i.e., mechanisms) such as working memory capac-
ity. Unfortunately, with a few notable exceptions (e.g., Beilock
et al., 2007; Johns et al., 2008; Rydell, McConnell, & Beilock,
2009;Schmader&Johns,2003;Schmaderetal.,2008), inves-
tigations of this sex difference rarely extend across multiple
levels of analysis. The present study was no exception. Because
our primary purpose was to establish as simply as possible
whether confidence mediates mental rotation performance, the
present experiments did not attempt to relate this factor to other
potential mediators or mechanisms.
Other Potential Mediators
In the introduction, we reviewed several studies demonstrating
that sex stereotypes can affect mental rotation performance.
Because we focused instead on confidence as a potential
mediator of mental rotation, the present experiments did not
manipulate or assess participants’ beliefs in or awareness of sex
stereotypes. However, many prior studies on gender role beliefs,
stereotype threat, and stereotype lift explicitly appeal to confi-
dence as a likely mediator between stereotypes and behavior
(see e.g., Schmader et al., 2008;Steele,1997; Walton & Cohen,
2003). In the domain of mathematics, for instance, stereotype
threat increases self-doubt (Steele & Aronson, 1995) and neg-
ative performance-related thoughts (Beilock et al., 2007;Cad-
inu et al., 2005) among women, whereas boosting females’ self-
evaluation eliminates the stereotype threat effect (Martens
et al., 2006;Rydelletal.,2009). In spatial tasks, women per-
form significantly better when they self-identify with scholastic
566 Arch Sex Behav (2012) 41:557–570
123
achievement (McGlone & Aronson, 2006), when told that the
test measures empathy (Massa et al., 2005), when told that
women are better than men at the task (Moe & Pazzaglia, 2006),
and when confident in their ability on masculine tasks (Moe
et al., 2009). All of these findings implicate confidence as a
likely mediator between sex stereotypes and performance on
spatial and mathematical tests.
Experience with spatial tasks is also related to mental rotation
performance (Baenninger & Newcombe, 1995; Casey, 1996;
Levine et al., 2005; Stericker & LeVesconte, 1982). Males tend to
engage in more spatial activities than females, such as sports and
action video games, and this factor predicts performance on spa-
tial tasks (Newcombe, Bandura, & Taylor, 1983; Quaiser-Pohl,
Geiser, & Lehmann, 2006; Terlecki & Newcombe, 2005; Voyer,
Nolan, & Voyer, 2000). However, the correlation between spatial
experience and performance is small (Baenninger & Newcombe,
1989; see also Scali, Brownlow, & Hicks, 2000). If spatial experi-
ence mediates spatial ability, then training on spatial tasks should
improve performance. Indeed, extensive training improves men-
tal rotation performance and attenuates the sex difference (Feng
et al., 2007; Lizarraga & Ganuza, 2003), but gains in performance
on trained stimuli typically do not generalize to untrained stimuli
(Kail & Park, 1990; Lohman & Nichols, 1990;Sims&Mayer,
2002). Thus, the improvement in performance may be attribut-
able to stimulus familiarity rather than task experience (Bethel-
Fox & Shepard, 1988;Sims&Mayer,2002; see also Kail et al.,
1979). These effects of spatial experience and stimulus famil-
iarity on mental rotation performance could, like the sex differ-
ence itself, be mediated by confidence. That is, practice and
familiarity could increase confidence and hence improve perfor-
mance on spatial tasks.
Biological models of the sex difference in spatial ability do not
account for the present results. Kimura (1999) argued that differ-
ential cortical lateralization and/or differential exposure to sex
hormones may explain the sex difference in spatial ability.
Casey (1996) also argued that the sexual dimorphism in spa-
tial ability is partially attributable to differential lateralization,
though she additionally posited that spatial experience con-
tributes to spatial ability. The present results do not exclude
these biological explanations. But if differential lateralization
and/or differential hormone exposure do contribute to the sex
difference in mental rotation, their influence is mediated by
confidence.
Possible Mechanisms
These experiments clearly demonstrate that confidence mediates
performance on the MRT, but they do not indicate how it does so.
One plausible account is that confidence affects the selection or
deployment of strategies for mental rotation. Researchers have
noted differential strategy use among participants (Schultz,
1991; Smith & Dror, 2001; Tomasino & Rumiati, 2004), with a
holistic strategy (i.e., rotating the object as a single entity) pro-
ducing better performance than an analytic strategy (i.e., rotating
the object part-by-part; Bethel-Fox & Shepard, 1988;Geiser,
Lehmann, & Eid, 2006;Kailetal.,1979;Moeetal.,2009). And
indeed, females are more likely than males to rotate analytically
(Cochran & Wheatley, 1989;Geiseretal.2006;Heil&Jansen-
Osmann, 2008). For instance, women rotate complex objects
more slowly than simple objects, thus suggesting an analytic strat-
egy. In contrast, men rotate complex and simple objects equally
fast, suggesting a holistic strategy (Heil & Jansen-Osmann,
2008).Itmaybethathighconfidence promotes holistic rotation,
whereas low confidence induces analytic rotation.
Other potential cognitive mechanisms are spatial atten-
tion and memory. In their integrative model of stereotype threat
effects, Schmader et al. (2008) argued that physiological stress,
performance monitoring, and suppression of negative stereo-
typic thoughts collectively deplete working memory, which
subsequently hinders performance on cognitive tasks. For
instance, when women are the target of a negative stereotype,
their working memory capacity is significantly reduced, and this
decrement in working memory capacity mediates the decline in
mathematical performance (Beilock et al., 2007; Johns et al.,
2008;Rydelletal.,2009;Schmaderetal.,2009;Schmader&
Johns, 2003) and logical reasoning (Regner et al., 2010). In the
present case, confidence might reduce stress or alleviate the
need to suppress negative thoughts, thereby liberating working
memory capacity for use on mental rotations. More directly
relevant is a recent study by Kaufman (2007), who showed that
mental rotation performance was predicted by spatial working
memory in particular. Relatedly, Fenget al. (2007) found that
males were better able to distribute attention across space, and
they concluded that the sex difference in mental rotation per-
formance was partially mediated by spatial attention. Thus,
some evidence indicates that sex differences in spatial attention
(Feng et al., 2007) and spatial working memory (Kaufman,
2007) contribute to the sex difference in mental rotation. It is
currently unclear whether participants’ confidence is related to
either or both of these mechanisms.
Conclusions
In sum, we found that confidence predicted performance both
between and within sexes (Experiment 1), that rendering con-
fidence irrelevant to the task reliably eliminated the sex differ-
ence in performance (Experiments 2 and 3), and that manip-
ulating confidence significantly affected performance (Experi-
ment 4). Given that mental rotation exhibits the largest sex
difference of any cognitive task (Halpern, 2000;Hines,2004;
Linn & Petersen, 1985; Maccoby & Jacklin, 1974), it is striking
that this effect was reliably evoked and eliminated in each of the
four experiments by such simple controls and manipulations.
Confidence at least partially explains the variability in mental
Arch Sex Behav (2012) 41:557–570 567
123
rotation performance within each sex, as well as the difference
between sexes. Thus, the sex difference in mental rotation appears
to be a difference of performance rather than ability. An impor-
tant endeavor for future research is to investigate how confi-
dence relates to other potential mediators and mechanisms of
this sex difference, such as sex stereotypes, spatial experience,
rotation strategies, working memory, and spatial attention.
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