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ORIGINAL PAPER
Sex Differences in Semantic Categorization
Vickie Pasterski •Karolina Zwierzynska •Zachary Estes
Received: 2 November 2010 / Revised: 21 March 2011 / Accepted: 28 March 2011 / Published online: 23 April 2011
Springer Science+Business Media, LLC 2011
Abstract Sex differences in certain cognitive abilities, includ-
ing aspects of semantic processing, are well established. How-
ever, there have been no reports investigating a sex difference in
semantic categorization. A total of 55 men and 58 women each
judged 25 exemplars of natural categories (e.g., FRUITS) and 25 of
artifact categories (e.g., TOOLS) as a nonmember, partial member,
or full member of the given category. Participants also rated
confidence for each judgment. Women provided a greater num-
ber of vague (partial member) judgments whereas men provided
more inclusive (full member) judgments of artifacts but more
exclusive (nonmember) judgments of natural categories. The sex
difference in vagueness was observed across domains (Cohen’s
d=.56). Confidence predicted categorization among both men
and women, such that more confident participants exhibited
fewer vague category judgments. However, men and women
were equally confident in their category judgments, and confi-
dence failed to explain the sex difference in categorization. Men
and women appear to categorize the same common objectsin sys-
tematically different ways.
Keywords Artifacts and natural kinds
Semantic categorization Sex differences
Introduction
Sex differences in certain aspects of cognition have been estab-
lished across domains and cultures (Kimura, 2002). Men and
women display, on average, different patterns of task performance
in domains such as spatial orientation and verbal or perceptual
skills (Kimura, 2002). For instance, men tend to excel on tasks of
spatial ability such as mental rotation (Linn & Petersen, 1985;
Voyer, Voyer, & Bryden, 1995), whereas women tend to excel
on tasks of linguistic ability such as verbal fluency (Kolb &
Wishaw, 1985;Spreen&Strauss,1991; for review, see Hines,
2009). Although there is substantial overlap between male and
female performance and cognitive abilities may be better char-
acterized by between-sex similarities rather than differences
(Hyde, 2005), studying sex differences in cognition is important
as it may elucidate mechanisms underlying sex-differentiated
behavior, which, in turn, may inform our understanding of sex
stereotypes (Hyde, 2007).
One aspect of cognition that has not been investigated in terms
of a sex difference, but could have broad implications, is semantic
categorization. Indeed, several studies indicate a sex difference in
processing natural categories (categories occurring indepen-
dently of human production or intention, such as FRUITS)aswellas
artifact categories (categories occurring by human production or
intention, such as TOOLS). Whereas women name natural objects
faster and more fluently, men name artifacts faster and more flu-
ently (Capitani, Laiacona, & Barbarotto, 1999; Laws, 1999).
Women also recognize natural objects more accurately, whereas
men recognize artifacts more accurately (Barbarotto, Laiacona,
Macchi, & Capitani, 2002). Similar effects have also been
observed in semantic priming, where natural category names facil-
itate subsequent judgments of their exemplars (e.g., FISH ?trout)
more strongly for women than for men, but artifact category
names facilitate judgments (e.g., TOOL ?hammer) more strongly
for men than for women (Bermeitinger, Wentura, & Frings,
V. Pasterski (&)
Department of Paediatrics, Addenbrooke’s Hospital, University of
Cambridge, Box 116, Level 8, Hills Road, Cambridge CB2 0QQ, UK
e-mail: vp265@cam.ac.uk
V. Pasterski K. Zwierzynska Z. Estes
Department of Psychology, University of Warwick, Coventry, UK
123
Arch Sex Behav (2011) 40:1183–1187
DOI 10.1007/s10508-011-9764-y
2008). Given this sex difference in semantic processing, we
hypothesized that categorization would also exhibit a sex differ-
ence.
A further finding with respect to natural and artifact categories
is that they differ in terms of vagueness, i.e., whether membership
in the given category is absolute (all-or-none) or graded (a matter
of degree; see Hampton, 2007). Artifact categories tend to be
judged with more vagueness than natural categories (Diesend-
ruck & Gelman, 1999;Estes,2003; Hampton, 1998; Rhodes &
Gelman, 2009). For example, a computer may partially belong in
the category TOOLS, but a tomato tends to be judged either com-
pletely in or completely out of the category FRUITS.Sogiventhe
sex difference in processing artifacts and natural objects, and
given that artifacts and natural objects differ in vagueness, we
tested whether men and women differ in the vagueness of their
category judgments.
In the present study, participants judged whether each of 50
items (e.g., tomato—FRUITS, computer—TOOLS) is a full member,
partial member, or nonmember of its target category, and they
were informed that‘‘Partial membership means that the item does
belong in the category, but not to the same extent as some other
items.’’ The percentage of partial membership judgments is a
measure of category vagueness (Estes, 2003), whereas the per-
centages of full member and nonmember judgments respectively
are measures of category inclusivity and exclusivity. Because
vague category judgments are associated with less confidence
(Estes, 2004), we also tested whether confidence was related to
the predicted sex difference in vagueness.
Method
Participants
A total of 113 students and staff at the University of Warwick
participated for £3 each. The mean age was 21.9 years for men
(N=55, SD =3.4) and 24.1 years for women (N=58, SD =
8.3). This difference in age was not significant. To check the
sample’s representativeness of men and women, participants’
sex-typedness was assessed via a retrospective version of the
Pre-school Activities Inventory (PSAI; Golombok & Rust,
1993). The PSAI is a robust 17-item measure of self-reported
masculinity and femininity. As expected, men (M=69, SD =
9.55) were significantly more masculine than women (M=40,
SD =15.13), t(111) =12.08, p\.001. In this case, we can
assume typicality for sex-typedness in the current sample.
Measures
A total of 25 target items from seven artifact categories and 25
target items from six natural categories were sampled from Estes
(2003). These target items were sampled on the basis of prior
studies in which the selected items were the most likely to elicit
disagreement between participants and uncertainty within par-
ticipants. Thus, all targets were‘‘borderline items’’for which cat-
egorymembershipisunclearandwhich were most likely to elicit
vague judgments (Hampton, 2007). Stimuli are shown in the
Appendix. Note that because most of these categories lack a clear
and consensual definition, participants’ judgments about these cat-
egories are subjective and hence are not classifiable as ‘‘correct’’
or ‘‘incorrect.’’ For example, because FISH is not a biologically
defined category, judging an item to belong or not belong in the
category is subjective.
Procedure
The items and their target categories were presented in random
order, and participants judged each item as a nonmember, partial
member, or full member of the given category. Instructions were
based on those used by Estes (2003). Using the example bil-
liards:SPORTS, the instructions read:‘‘If you believe that billiards
is not a sport, then you should check the nonmember box. Or if
you think that billiards is only somewhat a member of the cat-
egory, then you should check the partial member box. But if you
believe that it’s just as much a member of the category as any
other sport, then you should indicate that it’s completely a
member by checking the full member box…Partial membership
means that the item does belong in the category, but not to the
same extent as some other items.’’ After each category judg-
ment, participants also rated their confidence in that judgment
on a scale ranging from 1 =‘‘notatallconfident’’to5=‘‘c o m -
pletely confident.’’
Results
Confidence
We first examined whether participants’ confidence (i.e., mean
confidence ratings) predicted the vagueness of their category
judgments (i.e., percentage of ‘‘partial member’’judgments).
Indeed, more confident participants produced fewer vague cat-
egory judgments (r=-.33, p\.001), and this correlation was
observed among both men (r=-.27, p\.05) and women
(r=-.41, p\.01). This significant negative relationship
between confidence and vagueness corroborates prior research
(Estes, 2004). It also indicates that any sex difference observed in
vagueness might be due to a concomitant sex difference in confi-
dence. To test for such a sex difference, participants’ mean con-
fidence ratings were analyzed via a 2 (sex) 92 (domain) ANOVA.
Only the expected main effect of domain was significant, F(1,
111) =11.15, p\.001; artifact categories (M=4.07, SE =.05)
were judged with greater confidence than natural categories
(M=3.95, SE =.05) (see also Estes, 2004). For instance, par-
ticipants were more confident in their judgments of whether a
computer is a TOOL than of whether a tomato is a FRUIT.More
1184 Arch Sex Behav (2011) 40:1183–1187
123
importantly, men and women were equally confident in their
judgments (M=4.01, SD =.52), F\1. Thus, if there were a sex
difference in categorization, it would not be attributable to a sex
difference in confidence.
Categorization
Mean percentages of exclusive (‘‘nonmember’’), vague (‘‘partial
m e m b e r ’’) , a n d i n c l u s i v e (‘‘ f u ll member’’) category judgments
are summarized in Table 1(including effect sizes in d;Cohen,
1988). Participants’ mean percentages of vague category judg-
mentswereanalyzedviaa2(sex)92 (domain) ANOVA. In
corroboration of prior research (e.g., Estes, 2003), artifact cate-
gories were judged with more vagueness than natural categories,
F(1, 111) =118.01, p\.001. For example, participants were
more likely to judge that a computer is a partial member of the
TOOL category than to judge that a tomato is a partial member of
the FRUIT category. More importantly, however, sex also pre-
dicted vagueness, F(1, 111) =8.89, p\.01. Women provided
more vague category judgments than men across domains, i.e.,
sex and domain did not interact. The effect size of this sex dif-
ference in vagueness was medium (d=.56; see Table 1for effect
sizes within each domain). To be conservative, we also analyzed
these data with participants’ mean confidence ratings included
as a covariate (ANCOVA). With confidence statistically con-
trolled, the sex difference in vagueness remained significant, F(1,
110) =10.01, p\.01. Thus again, the sex difference in vagueness
was not attributable to confidence.
Having observed a robust sex difference in vagueness, we
next examined whether it was complemented by a sex differ-
ence in exclusivity, inclusivity, or both. That is, given that men
exhibited fewer ‘‘partial member’’judgments, did they exhibit
more ‘‘nonmember’’ judgments or more ‘‘full member’’ judg-
ments than women? Participants’ mean percentages of exclu-
sive (nonmember) and inclusive (full member) judgments were
analyzed via a 2 (sex) 92 (domain) MANOVA. Sex and domain
interacted significantly in exclusive judgments, F(1, 111) =4.75,
p\.05, and marginally in inclusive judgments, F(1, 111) =3.28,
p=.07. As evident in Table 1, men exhibited significantly more
inclusive judgments of artifacts, t(111) =2.36, p\.05, but sig-
nificantly more exclusive judgments of natural categories,
t(111) =2.29, p\.05. For instance, men were more likely than
women to judge that a computer is a full member of the TOOL
category, and that a tomato is not at all a FRUIT. These sex dif-
ferences were also medium, with effect sizes of .44 and .43 in the
artifact and natural categories respectively.
Finally, we also tested the generality of these results across
items rather than participants. Mean percentages of exclusive,
vague, and inclusive judgments were analyzed via a 2 (sex) 92
(domain) MANCOVA, with confidence included as a covariate.
The pattern of results replicated that described above: Vague
judgments exhibited significant main effects of sex, F(1, 47) =
5.78, p\.05, and domain, F(1, 47) =150.16, p\.001, without
interaction, whereas significant interactions were observed in
both exclusive judgments, F(1, 47) =8.35, p\.01, and inclu-
sive judgments, F(1, 47) =8.47, p\.01.
Discussion
This study yielded three novel findings. First, these results
revealed a domain-general sex difference in vagueness (d=
.56). Women provided more vague judgments than men in both
artifact and natural categories. Although prior studies have dem-
onstrated sex differences in naming (Capitani et al., 1999;Laws,
1999), recognition (Barbarotto et al., 2002), and semantic prim-
ing (Bermeitinger et al., 2008) of artifact and natural objects, the
present study provided the first demonstration of a sex difference
in the categorization of such objects. So whereas prior studies
have revealed differences in the speed and/or accuracy of partic-
ipants’ responses, the present study showed a sex difference in
actual judgments. Men and women categorized the same com-
mon objects in systematically different ways.
Second, we also found a domain-specific sex difference in
absolute judgments. Relative to women, men provided more
inclusive judgments of artifacts and more exclusive judgments
of natural categories. This finding is broadly consistent with the
prior demonstrations of a sex difference in semantic processing,
with men and women exhibiting superior processing of artifacts
and natural objects respectively (Barbarotto et al., 2002;Capi-
tani et al., 1999;Laws,1999). For example, in the semantic
fluency task administered by Capitani et al. (1999), men pro-
duced more instances of the category TOOLS, whereas women
produced more instances of FRUITS. Men’s superior fluency with
artifact categories may, in fact, be related to the greater inclu-
sivity of their artifact categories. That is, if men have more
inclusive artifact categories than women, it follows that they
would have more instances upon which to draw in the semantic
fluency task. And, conversely, the greater exclusivity of men’s
natural categories might also be related to their inferior fluency
in naming natural objects.
Table 1 Percentages of exclusive (nonmember), vague (partial mem-
ber), and inclusive (full member) category judgments of artifact and
natural categories by men (N=55) and women (N=58)
Domain Judgment Men Women pd
MSEMSE
Artifactual Exclusive 20.15 2.10 20.55 1.96 ns .03
Vague 45.82 2.75 52.76 2.19 .05 .37
Inclusive 34.04 2.42 26.69 1.99 .02 .44
Natural Exclusive 44.07 2.78 35.10 2.76 .02 .43
Vague 21.45 2.29 30.28 2.39 .01 .50
Inclusive 34.47 2.29 34.62 2.45 ns .00
Arch Sex Behav (2011) 40:1183–1187 1185
123
A third novel finding of this study was that participants’ con-
fidence predicted their categorization, but confidence failed to
explain the observed sex differences in categorization. Confi-
dence negatively predicted vagueness among both men and
women, such that more confident participants provided fewer
vague category judgments (cf. Estes, 2004). However, men and
women were equally confident in their category judgments, and
statistically controlling participants’ confidence failed to eliminate
the sex difference in vagueness. Thus, the sex difference in cate-
gorization was not attributable to a sex difference in confidence.
Rather than indicating a sex difference in semantic categori-
zation per se, this result could instead reflect a general tendency
for women to choose more moderate responses than men. That is,
women might simply be more likely to select a middling or mid-
scale response, whereas men might be more likely to select an
extreme or endpoint response, regardless of the task. If so, then the
aforementioned sex difference would say little about categori-
zation in particular. We used participants’ confidence ratings to
test this potential explanation. We calculated for each participant
the percentage of confidence ratings that were moderate, opera-
tionally defined as any response of 2, 3, or 4 on the 1-to-5 confi-
dence scale. Contrary to the moderation hypothesis, women were
no more likely than men to select moderate confidence ratings
(t\1). Thus, the sex difference in category judgment appears to
be a genuine sex difference in semantic categorization rather than
a sex difference in scale use.
The sex difference in categorization is also consistent with a
sex difference in the use of tentative language. In general, women
tend to use more tentative language such as hedges (e.g.,‘‘sort of’’)
a n d d i s c l a i m e r s ( e . g . , ‘‘ I ’ m n o t s u r e ’’; C a r l i , 1990). This tendency
is particularly evident when discussing masculine topics such as
sports; when discussing feminine topics such as fashion, how-
ever, men use more tentative language than women (Palomares,
2009). This sex difference in tentative language may reflect the
sex differences in exclusive and inclusive judgments demon-
strated here.
The present study also replicated a domain difference in cate-
gorization (Diesendruck & Gelman, 1999;Estes,2003; Hampton,
1998,2007; Rhodes & Gelman, 2009), such that artifact catego-
ries were judged with greater vagueness than natural categories.
This effect is typically attributed to a domain difference in cat-
egory representation. Whereas artifact categories are primarily
represented according to their functions, which are mutable,
natural categories tend to be represented according to their
appearance and biological features, which are less mutable (e.g.,
Hampton, Storms, Simmons, & Heussen, 2009). More impor-
tantly for our purposes, this replication supports the validity of our
sample.
This sex difference in categorization could have important social
implications in career choices and performance. The differential
tendency for absolute judgments may partially explain the gender
gap in fields that allow more or less precision or vagueness, such
as sciences and humanities. Furthermore, categorization may also
affect performance within one’s chosen profession. For instance,
male doctors may be more or less likely than female doctors to
diagnose a given set of symptoms as a disease. The potential
consequences are manifold, and further studies may be fruitful.
Acknowledgment This study was funded by the Undergraduate Research
Scholarship Scheme (URS) at the University of Warwick.
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Appendix Stimuli
Domain
Artifactual Natural
Category Exemplar Category Exemplar
Clothing Headband Animals Bacterium
Pocket Fungus
Furniture Clock Virus
Piano Yeast
Refrigerator Fish Clam
Shelves Crab
Ships Canoe Lobster
Kayak Octopus
Raft Plankton
Spacecraft Seahorse
Tools Computer Shrimp
Funnel Squid
Paint Fruits Avocado
Toys Backgammon Coconut
Cards Cucumber
Guitar Rhubarb
String Tomato
Vehicles Horse Insects Caterpillar
Roller skates Leech
Tricycle Scorpion
Wheelchair Spider
Weapons Car Worm
Chair Mammals Goose
Drugs Vegetables Pumpkin
Fingernails Rice
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