ArticlePDF Available

Women Favour Dyadic Relationships, but Men Prefer Clubs: Cross-Cultural Evidence from Social Networking

Authors:

Abstract and Figures

The ability to create lasting, trust-based friendships makes it possible for humans to form large and coherent groups. The recent literature on the evolution of sociality and on the network dynamics of human societies suggests that large human groups have a layered structure generated by emotionally supported social relationships. There are also gender differences in adult social style which may involve different trade-offs between the quantity and quality of friendships. Although many have suggested that females tend to focus on intimate relations with a few other females, while males build larger, more hierarchical coalitions , the existence of such gender differences is disputed and data from adults is scarce. Here, we present cross-cultural evidence for gender differences in the preference for close friendships. We use a sample of *112,000 profile pictures from nine world regions posted on a popular social networking site to show that, in self-selected displays of social relationships , women favour dyadic relations, whereas men favour larger, all-male cliques. These apparently different solutions to quality-quantity trade-offs suggest a universal and fundamental difference in the function of close friendships for the two sexes.
Content may be subject to copyright.
RESEARCH ARTICLE
Women Favour Dyadic Relationships, but
Men Prefer Clubs: Cross-Cultural Evidence
from Social Networking
Tamas David-Barrett
1
*, Anna Rotkirch
2
, James Carney
1
, Isabel Behncke Izquierdo
1
,
Jaimie A. Krems
3
, Dylan Townley
1
, Elinor McDaniell
1
, Anna Byrne-Smith
1
, Robin I.
M. Dunbar
1
1Department of Experimental Psychology, University of Oxford, South Parks Rd, Oxford, OX1 3UD, United
Kingdom, 2Population Research Institute, Väestöliitto, Kalevankatu 16, 00101, Helsinki, Finland, 3
Department of Social Psychology, Arizona State University, Tempe, AZ, 85287, United States of America
*tamas.david-barrett@psy.ox.ac.uk
Abstract
The ability to create lasting, trust-based friendships makes it possible for humans to form
large and coherent groups. The recent literature on the evolution of sociality and on the net-
work dynamics of human societies suggests that large human groups have a layered struc-
ture generated by emotionally supported social relationships. There are also gender
differences in adult social style which may involve different trade-offs between the quantity
and quality of friendships. Although many have suggested that females tend to focus on inti-
mate relations with a few other females, while males build larger, more hierarchical coali-
tions, the existence of such gender differences is disputed and data from adults is scarce.
Here, we present cross-cultural evidence for gender differences in the preference for close
friendships. We use a sample of *112,000 profile pictures from nine world regions posted
on a popular social networking site to show that, in self-selected displays of social relation-
ships, women favour dyadic relations, whereas men favour larger, all-male cliques. These
apparently different solutions to quality-quantity trade-offs suggest a universal and funda-
mental difference in the function of close friendships for the two sexes.
Introduction
The recent literature on both the evolution of sociality and the network dynamics of human
and animal societies [18] suggests that large social groups cannot be fully connected: they
have a layered structure that is generated by emotionally supported social relationships [915].
Although there are structural aspects to social organisation, individual behaviour is crucially
shaped by dyadic relationships. It may be that preferred patterns of relationships vary by gen-
der in a way that typically reflects sex differences in reproductive strategies [1619].
For instance, friendships or close and prolonged affiliation with non-kin are characterised
by homophily, so that people typically choose friends of the same age and gender (for recent
PLOS ONE | DOI:10.1371/journal.pone.0118329 March 16, 2015 1/15
OPEN ACCESS
Citation: David-Barrett T, Rotkirch A, Carney J,
Behncke Izquierdo I, Krems JA, Townley D, et al.
(2015) Women Favour Dyadic Relationships, but
Men Prefer Clubs: Cross-Cultural Evidence from
Social Networking. PLoS ONE 10(3): e0118329.
doi:10.1371/journal.pone.0118329
Academic Editor: Luo-Luo Jiang, Wenzhou
University, CHINA
Received: April 12, 2014
Accepted: January 3, 2015
Published: March 16, 2015
Copyright: © 2015 David-Barrett et al. This is an
open access article distributed under the terms of the
Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any
medium, provided the original author and source are
credited.
Data Availability Statement: All relevant data are
within the paper and its Supporting Information files.
Funding: This study was supported by EU FP7 EINS
grant agreement No 288021 to TDB, European
Research Council Advanced grant to RD, EU Marie
Curie Fellowship, grant agreement No 297854 to JC.
The funders had no role in study design, data
collection and analysis, decision to publish, or
preparation of the manuscript.
Competing Interests: The authors have declared
that no competing interests exist.
reviews see [2022]). Sex differences in reproductive strategies also shape adult social behav-
iour [20,2326] and may reflect different trade-offs between the quantity and quality of friend-
ships. Thus, it has been suggested that females invest more heavily in a few, high-quality and
time-consuming friendships, while males prefer groups with less investment per member, and
higher group cohesion [2730].
There is reason to believe these gender differences have evolutionary roots. First, sex differ-
ences in friendship emerge early [31], are quite apparent already in small children and appear
to increase with age [21,32,33]. Second, similar gender patterns exist in some non-human pri-
mates [13,34]. One obvious explanation is that male peer sociality evolved to enable hunting,
coalitionary support for within-group dominance, and/or defence in larger groups, while wom-
ens peer sociality is to a greater extent shaped by their higher investment in reproduction and
child rearing, as well as their historically more frequent experience of out-migration and the
need to integrate into a patrilocal society with few, if any, kin [18,20,25]. Patrilocality is also the
norm for chimpanzees and bonobos, lending further support to female transfer being the norm
throughout hominin evolution [35,36].
However, the scope of human gender differences is disputed. Several studies found few sex
differences in the number of close non-related friends that an individual turns to for help and
assistance [4,3742] while others detect crucial differences in the quantity and intensity of
male and female peer ties [16,23,24,30,32,4345]. Sex differences also depend on which compo-
nent of friendship is being studied, as well as the age and culture of the subjects. For instance,
the review by Rose and Rudolph [21] found that girls have a greater preference for extended
dyadic interactions and prosocial behaviour, while boys interact more in peer groups with a
high network density and clear dominance hierarchy. But gender differences are negligible con-
cerning the expectations males and females have of friends and in the symmetrical reciprocity
they expect from them [22]. In any case, documented sex differences tend to be small or medi-
um-size rather than large [22,46].
All reviews stress the need for more friendship research on adults and on people from other
than WEIRD[47] societies [21,22,46]. Most research on friendships has involved children or
teenagers, and there is to date only limited and mixed evidence for gender differences in adult
human friendships [20,38,4850]. Here, we use data from a social media site to explore gender
differences in close peer relations. We hypothesised that social relations among same-aged
adults would exhibit gender homophily and would vary by gender, such that men would exhib-
it higher numbers of friends compared to women.
Methods and Data
To investigate close friendships in the two sexes, we used Facebook Profile Pictures following
the example of recent literature that deals with social networking data [5154]. Facebook is the
most popular global social networking site, the primary function of which is to fulfil psychoso-
cial needs for belonging and self-presentation [55]. Upon signing up, each user may choose a
Profile Picture, which represents the user to the rest of the Facebook community, is public, and
appears at the top of the users profile and as the icon next to the users name wherever he or
she posts on the site. Each user can have only one Profile Picture at a time. Usually the picture
features the user only. When the picture displays peers they tend to be the user with friends or
acquaintances [51]. The choice of profile pictures is related to the users desired impression for-
mation [55]. This impression is not, however, too detached from the real world: Facebook user
profiles have been found to reflect actual rather than idealised identities [56]. We thus assume
that Profile photographs of peers are likely to align with behavioural inclinations, and thus pro-
vide a reliable proxy for relationship preferences.
Women Favour Dyadic Relationships, but Men Prefer Clubs
PLOS ONE | DOI:10.1371/journal.pone.0118329 March 16, 2015 2/15
Data collection
We used random search terms to select 309 users (seeds) of Facebook who shared their batch
of friends publicly. (The 309 users had on average 362 friends.) In the first wave of data collec-
tion, we located the Profile Pictures of all the friends of each of these users (111,863 Profile Pic-
tures in total); each photograph was categorised with respect to the type of the picture, and the
number and gender of the persons displayed (see Table 1). Data collection took place between
July 2011 and January 2012.
Additional information was collected in two further waves. In the first of these (wave 2),
geographical data based on geographical location was collected to control for cultural differ-
ences. The coders were provided with a list of geographic regions: Europe (56 seeds), Central
and South Asia (16), Latin America (9), Middle East and North Africa (14), North America
(14), South East Asia (43), Sub-Saharan Africa (7), Australia (9), East Asia (19), or cant tell re-
gion(21). In the second (wave 3), we used a finer classification of the number of people shown
in Profile Pictures: the first two waves classified all pictures with four or more individuals as a
single category, but in wave 3 this was extended to specify individual numbers up to 20.
The coding was done by 8 coders, all but two of whom were research assistants at the Uni-
versity of Oxford. All coders bar one (the lead author) were blind during the coding phase,
knowing only that the project was to study gender differences on social networking sites. Cod-
ers were instructed to avoid any discussion of the project amongst themselves during the cod-
ing phase. All results presented in this paper are robust to the elimination of each of the coders,
each of the regions, and the type of Profile Pictures displayed by the seeds.
We used only publicly available pictures. No pictures or other information associated with
this research was either separately downloaded or stored. The research project was approved
Table 1. Coding categories.
Code Description Tally %
NH Not human picture: e.g., object, landscape, monster, car, or any picture with an
animal
13,861 12.9
NA Not publicly available (or Facebook default prole) 1,626 1.5
NP Multiple people but not peer: e.g., mother-child, a family 2,651 2.5
CB Child or baby 3,470 3.2
MP Multiple pictures, collage 1,961 1.8
CTG Cant tell gender 2,447 2.3
1F 1 female 32,208 30
2F 2 females 3,508 3.3
3F 3 females 945 0.9
4F 4 females 384 0.4
1M 1 male 30,279 28.2
2M 2 males 2,326 2.2
3M 3 males 935 0.9
4M 4 males 388 0.4
1F1M 1 female + 1 male (e.g. a couple) 6,769 6.3
1F2M 1 female + 2 males 329 0.3
2F1M 2 females + 1 male 359 0.3
1F3M 1 female + 3 males 106 0.1
2F2M 2 females + 2 males (e.g. two couples) 185 0.2
3F1M 3 females + 1 male 110 0.1
5+ Five or more people on the picture 2,433 2.3
doi:10.1371/journal.pone.0118329.t001
Women Favour Dyadic Relationships, but Men Prefer Clubs
PLOS ONE | DOI:10.1371/journal.pone.0118329 March 16, 2015 3/15
by the Central University Research Ethics Committee of University of Oxford, and each coder
received a full research ethics briefing before joining the coding team.
Data exclusion
As adult interpersonal processes were our focus here, we excluded all Profile Pictures that con-
tained a non-human figure, a baby or child, people of markedly different ages (as judged by the
coders), pictorial collages (i.e. pictures composed of multiple, distinct or coloured photos), a
person or people whose gender(s) were unidentifiable or that did not contain a person. 81,246
Profile Pictures remained, of which 19,984 (26%) contained more than one person. For an
overview of the data see Fig. 1.
Results
Gender homophily
First, we studied gender homophily in profile pictures. As expected, if the Profile Pictures dis-
played three or more persons (7.6% of Profile Pictures displaying adults), they tended to be the
same gender, confirming our gender homophily hypothesis (Fig. 1).
Fig 1. The ratio of men in Profile Pictures (with same age adults only) as a function the number of persons in the picture. The value corresponding to
each nadds up to 1. The size of the disks denotes the share in the ratio at that particular bin. Crossing points on the grid are the only possible points given the
discrete nature of the data.
doi:10.1371/journal.pone.0118329.g001
Women Favour Dyadic Relationships, but Men Prefer Clubs
PLOS ONE | DOI:10.1371/journal.pone.0118329 March 16, 2015 4/15
The gender ratio on Profile Pictures persons exhibited a tri-modal distribution (see Fig. 2).
In Profile Pictures with 512 persons, the frequencies for women-only, men-only, and equal
gender ratios are 15.5%, 40.6%, 15.7%. (Note that for n<5 the trimodality cannot exist, while
for very large nthe male groups dominate to such an extent that only one modality is left.)
These are above the frequencies for all other combinations: pictures with both genders but un-
equally represented (such as one woman and two men) were significantly less common. Given
that the population mean is approximately balanced, this finding suggests a strong
gender homophily.
This preference for same-sex friends was further supported by the subsample that contains
Profile Pictures displaying fewer than 5 people. While pictures with two persons showed a
higher mixed than same gender frequency (sample average (2F+2M)/1F1M-1 = -0.123 (boot-
strapping mean -0.122 and s.d. 0.044), likely indicative of pictures of romantic couples, both
the 3-person pictures (sample average 2(3F+3M)/(1F2M+2F1M)-1 = 4.34 (bootstrapping
mean 4.36 and s.d. 0.39) and the 4-person pictures (sample average 3(4F+4M)/(1F3M+2F2M+
3F1M)-1 = 4.78 (bootstrapping mean 4.75 and s.d. 0.51) had a much higher same-gender fre-
quency compared to mixed-gender frequency (Fig. 3A).
Male propensity towards displaying more people
Studying the gender composition of peer groups indicated that, when Profile Pictures display a
large group of people, they tend to be all male, which was in line with our expectations. In
Fig 2. Relative frequencies of different gender ratios for groups where 5<=n<= 12. The distribution shows a trimodal pattern with women-only,
gender-equal and men-only gender ratios significantly above zero.
doi:10.1371/journal.pone.0118329.g002
Women Favour Dyadic Relationships, but Men Prefer Clubs
PLOS ONE | DOI:10.1371/journal.pone.0118329 March 16, 2015 5/15
Fig 3. Bootstrap histograms. Panel (a): the ratio of same gender Profile Pictures compared to mixed
gender profile pictures (probability corrected); green, red, and blue lines correspond to n = 2, 3, and 4. Panel
Women Favour Dyadic Relationships, but Men Prefer Clubs
PLOS ONE | DOI:10.1371/journal.pone.0118329 March 16, 2015 6/15
groups of three or four persons, men and women had the same propensity to appear in same-
gender Profile Pictures (Table 1). However, larger groups were predominantly male, and in-
creasingly so as the group size grows (Fig. 4).
The male propensity to be part of larger groups was further supported by the fact that men
appear together with more people than do women (Fig. 3B). For groups with 24 peers of the
same gender, men appeared in pictures with 2.47 people on (bootstrapping mean 2.47, s.d.
0.01), as opposed to 2.35 of women (bootstrapping mean 2.35, s.d. 0.01), which are significantly
different from each other (p<0.0001). For groups with 220 peers of any gender, men appeared
with 2.90 (bootstrapping mean 2.90, s.d. 0.07), as opposed to 2.54 of women (bootstrapping
mean 2.54, s.d. 0.05) which are also significantly different from each other (p<<0.0001). This
suggests that independently of gender combinations and group size, men tend to appear with a
larger number of people displayed in Profile Pictures.
(b): the number of people on a Profile Picture men (red) or women (blue) appear on; straight lines: same
gender with nbetween 2 and 4, dashed lines: mixed gender with nbetween 2 and 4, dotted lines: mixed
gender with nbetween 2 and 20. Panel (c): the ratio of the frequency of same-gender pictures between the
genders; green: pictures with 1 person, red: 2 persons, brown: 3 persons, and blue: 4 persons. (100,000
bootstrapping repeats.)
doi:10.1371/journal.pone.0118329.g003
Fig 4. The ratio of same-gender women-only to men-only frequencies (nF/nM as function of n). Gray lines denote a one-standard-deviation band from
bootstrapping. Above n>4, men-only groups dominate, while women-only groups become extremely rare. The linear OLS coefficient of nF/nM as a function
of n is negative, with R
2
= 0.86, and p<0.01
doi:10.1371/journal.pone.0118329.g004
Women Favour Dyadic Relationships, but Men Prefer Clubs
PLOS ONE | DOI:10.1371/journal.pone.0118329 March 16, 2015 7/15
Women focus on dyadic relationships
Finally, we detected an unexpectedly strong female focus on same gender dyads. Women not
only tended to appear in Profile Pictures displaying a smaller number of people, as expected in
the second research hypothesis, but there was also a strong preference towards pictures con-
taining two women (Fig. 3C). There were 50.8% more pictures with two female peers than pic-
tures with two male peers (bootstrapping mean 51.5, s.d. 14.8). This is especially remarkable
given that same-gender pictures with 1, 3, or 4 or more people had an almost perfect gender
balance: there were only 6.4% more pictures with one woman only in our dataset than with one
man only (bootstrapping mean 7.2, with s.d. 14.1), only 1.1% more pictures with three women
than with three men (bootstrapping mean 1.7, s.d. 10.8), and 1.0% fewer pictures with four
women compared to four men (bootstrapping mean 0.5, s.d. 12.5).
Cultural variation
Although there was substantial variation across the different world regions, the main patterns
of our findings were present in each of them(Fig. 5A-C), with only the magnitude of the effect
varying. While a selection bias may theoretically have affected the relatively small local varia-
tion of our results, we find this unlikely: the seeds were randomly selected and at the time of
the data collection 17% of the global adult population was using Facebook. Furthermore, mea-
sures for other than our three main findings reported above were less uniform among the
world regions (Fig. 5D).
Follow-Up Studies
It is possible that the relative prevalence of female-female Profile Pictures in comparison to
male-male ones may not reflect friendship behaviour but either (a) a female preference for put-
ting up pictures of two people of any gender, or (b) a reluctance among men to display pictures
with two male friends, especially in regions where homophobia is common. We tested both of
these alternative explanations.
First, we tested whether there is a gender difference in the preference for Profile Pictures
containing two people only. We randomly selected 960 new profiles on Facebook with two
same-aged individuals on them. Out of the 960, we were unable to determine the gender of the
account user in 11 cases. Out of the remaining 949 cases, 493 pictures belonged to a man and
456 belonged to a woman. Given the fact that the overall Facebook participation gender ratio is
almost balanced, this result suggests that the probability of women having a strong preference
to put up pictures of two people of any gender is negligible.
Second, we tested if homophobia in the country where the seed owner of the Facebook ac-
count lived would affect the ratio between female and male same-gender two-person pictures.
(To correct for the fact that different countries have different gender ratios among Facebook
users, we used the (2F/1F)/(2M/1M)-1 measure.) As a measure of homophobia, we used the
country level geographical codes of our data, and the corresponding homophobia index for
these countries as calculated by Pew Global [57]. As the homophobia index of Pew Global cov-
ers only the largest 52 countries, we could not test this hypothesis on our entire database. For
the remaining seeds, countries were coded to be low on homophobia if they scored between 0
and 40 for the question Homosexuality is a way of life that should be accepted by societyand
to be high homophobic countries if they scored between 60 and 100. This gave us 66 seeds liv-
ing in countries with low homophobia and 47 seeds in countries with high homophobia. The
(2F/1F)/(2M/1M)-1 mean for the two groups were 0.63 and 0.52, respectively (Fig. 6). As the
difference is not statistically significant (p = 0.12), and is in the opposite direction to that
Women Favour Dyadic Relationships, but Men Prefer Clubs
PLOS ONE | DOI:10.1371/journal.pone.0118329 March 16, 2015 8/15
predicted by the hypothesis, we can conclude that male homophobia is not associated with the
difference between 2F vs 2M frequencies in our dataset.
Discussion
Human societies are complex, large-scale communities of multi-generational social networks.
At base, however, these networks are built of the small-scale personal networks of individuals.
Our data shed light on the dynamics of these personal networks by providing strong cross-
cultural evidence for the universality of a male propensity to prefer a higher number friend-
ships compared to women. While large women-only groups were almost non-existent in self-
selected Profile Pictures, males were more likely to present themselves as part of large all-male
groupsarguably an essential element of male-male coalitional competition. Our results are
Fig 5. Cultural variation in the main finding. Panel (a): the ratio between same-gender and mixed gender pictures of different group size (corrected by the
probability of appearance, see text). Panel (b): number of close friends (same gender, with groups size 2 to 4). Panel (c): the ratio between same-gender
Profile Pictures as a function of group size (1F/1M normalised to 0). Panel (d): cultural variation in the proportion of single person pictures within all Profile
Pictures in a given global region. (Region codes of Panels a-c: green: Central and South Asia, blue: Europe, dashed blue: Latin America, dashed green:
Middle East and North Africa, dotted blue: North America, dotted green: South-East Asia, red: Sub-Saharan Africa, black: Australia, dashed black: East
Asia.)
doi:10.1371/journal.pone.0118329.g005
Women Favour Dyadic Relationships, but Men Prefer Clubs
PLOS ONE | DOI:10.1371/journal.pone.0118329 March 16, 2015 9/15
broadly in line with many previous studies of human friendship [27,30,58,59] which also
found strong gender homophily and male preference for coalitions. This difference in the pre-
ferred number of friends may signal different solutions to the quantity-quality trade-off in so-
cial ties. The emotional quality of a relationship is a positive function of the time invested in it
[39,60], and the closer and more time-demanding a relationship one has, the less time can be
devoted to others [11,24]. At the same time, the amount of social capital available that individ-
uals have to distribute among the members of their personal social networks is limited [61,62].
It thus appears as if women build a densenetwork, while men make alliances based on loose
networks. We also found gender similarity in the preferences for three and four friends,
which may explain part of the inconclusive results in previous studies on sex differences in
friendship numbers.
The male propensity to form coalitions could have emerged from the sexual division of la-
bour in ancestral environments. It was a male responsibility to defend the group against attack
from outsiders, and to do so successfully it was necessary that men band together [20,24]. In
males but not females, then, out-group defence called for coalitional cooperation
and behaviour.
Our finding that women prefer to picture themselves with fewer friends, and thus appear
more often to focus their social capital on only one person at a time, suggests a strong female
preference for dyadic relations. The social benefits of such a female dyadic social style are
harder to pin down, but three alternative hypotheses might be suggested. First, females may
have developed a propensity to form dyadic same-sex friendships as a response to the chal-
lenges of their social environments. Given the likelihood of ancestral patrilocality
Fig 6. Homophobia is not related to the frequency of 2F Profile Pictures, bootstrapping distributions. Blue line: highly homophobic countries; red line:
countries with low homophobia (see text for definitions). Dashed black line: the (2F/1F)/(2M/1M)-1 mean of the entire database. (100,000 bootstrapping
repeats.)
doi:10.1371/journal.pone.0118329.g006
Women Favour Dyadic Relationships, but Men Prefer Clubs
PLOS ONE | DOI:10.1371/journal.pone.0118329 March 16, 2015 10 / 15
[35,36,63,64], adolescent females would often have entered communities where they had few
or no close kin. For females especially, the presence of kin is fitness-enhancing, as has been re-
peatedly shown for both anthropoid primates [65,66] and humans [67,68]. Thus the formation
of emotionally intense, exclusive and sisterlydyadic bonds may have been a means to essen-
tially replace kin [25] and to defend against male and inter-female aggression in the new com-
munity where she did not have female kin [25,69,70]. This mirrors the case of patrilocal
bonobos (Pan paniscus), where females enter foreign communities in adolescence and integrate
into their new group through intense bond formation with another (typically older) female
[71]. A second explanation posits that, since females are the driving agents in human pair-
bond formation, it may be a female-specific sexual strategy to form exclusive dyadic relation-
ships. In this framework, the high frequency of female-female dyads in womens lives might be
a by-product of a preference for pairbonding [12]. A third explanation focuses on females
unique capacity for intense empathic relationships, derived from the mother-infant bond. In
this model, heightened female empathy creates an emphasis on individual relationships as a
consequence of the psychological toolbox of mothering [72,73]. In comparison, males generally
neither have nor require this capacity, and hence they form less emotionally close bonds, those
of friendship included.
These three explanations for gender differences in social stylepatrilocality, pair-bonding
and maternal empathyare difficult to tease apart. Not only is the evolutionary origin of all
primate bonding likely to have arisen out of the mother-infant relationship [74], whatever
forces shaped female friendship thereafter, different ultimate causes (e.g., defence against ag-
gression in a patrilocal society, or assistance among maternal kin) may have used similar proxi-
mate mechanisms (e.g., high reliance on intimate disclosure) making it hard to dissociate
them. Furthermore, recent studies of close friendship as a function of age suggests that women
switch their primary focus from female-female friendships to pairbonding and then to mother-
daughter bonding at different stages of the life cycle [75].
The importance for a female of maintaining close relationships once she has left her natal
group sheds light on the strategies that women use during intrasexual aggression (notably ex-
clusion and relationship-ending gossip [29,69]). If a females bonds to friends and her spouse
are crucial for accessing resourcesfrom food to informationthen breaking these bonds
and/or excluding the female all together can radically affect that individuals fitness, to the ben-
efit of her competitors.
There are, inevitably, some potential limitations to our data. We cannot be sure that co-ap-
pearance on Profile Pictures always reflects real-life social ties. Future research is needed in
order to assess gender differences in offline sociality. However, no existing research suggests
that profile pictures would include imagined or random social relations to any significant ex-
tent (not least because the other person is likely to object) and our results are in line with other
recent findings from online social communities [50]. Displaying Profile Pictures with two or
more people compared to only one person may also reflect some unknown personal psycholog-
ical characteristics or specific life-events of account users; however, such possible characteris-
tics should not affect our main results.
In summary, our results point to striking gender differences in intimate friendship strate-
gies: women prefer close dyadic bonds (with evolutionary origins in either pairbonding or so-
cial insurance purposes, or both), whereas men use their bonding capacity to build multimale
groups (in effect, clubs). This concurs with work on chimpanzees, where females form tight,
kin-based networks and males make loose, easy-to-break alliances [76]. Since similar gendered
bonds are found in our closest primate relatives, they may long predate the evolution of our
species. Among cercopithecine primates, females are disproportionately more likely to invest
in core female friendshipswith matrilineal relatives as group size gets larger, apparently in
Women Favour Dyadic Relationships, but Men Prefer Clubs
PLOS ONE | DOI:10.1371/journal.pone.0118329 March 16, 2015 11 / 15
order to maximise the effectiveness with which these relationships function as social buffers
[1,12,65]. By contrast, chimpanzees [34] and humans may show a tendency to form close
friendships with unrelated females in addition to those they might form with close
female relatives.
Supporting Information
S1 Data. Anonymised profile picture frequency database.
(CSV)
Acknowledgments
We thank Elena Denaro, Joshua de Gastyne, Erin Simmons, and Cathal Power for assistance in
data collection.
Author Contributions
Conceived and designed the experiments: TDB. Performed the experiments: TDB AR DT EM
ABS. Analyzed the data: TDB. Wrote the paper: TDB AR JC IBI JK RD.
References
1. Lehmann J, Dunbar RIM (2009) Network Cohesion, Group Size and Neocortex Size in Female-bonded
Old World Primates. Proceedings of the Royal Society B-Biological Sciences 276: 44174422. doi: 10.
1098/rspb.2009.1409 PMID: 19793756
2. Hill RA, Dunbar RIM (2003) Social network size in humans. Human Nature-an Interdisciplinary Bioso-
cial Perspective 14: 5372.
3. Krause J, Lusseau D, James R (2009) Animal social networks: an introduction. Behavioral Ecology and
Sociobiology 63: 967973.
4. Apicella CL, Marlowe FW, Fowler JH, Christakis NA (2012) Social networks and cooperation in hunter-
gatherers. Nature 481: 497501. doi: 10.1038/nature10736 PMID: 22281599
5. Kanai R, Bahrami B, Roylance R, Rees G (2012) Online social network size is reflected in human brain
structure. Proc Biol Sci 279: 13271334. doi: 10.1098/rspb.2011.1959 PMID: 22012980
6. David-Barrett T, Dunbar RI (2012) Cooperation, behavioural synchrony and status in social networks. J
Theor Biol 308: 8895. doi: 10.1016/j.jtbi.2012.05.007 PMID: 22609470
7. David-Barrett T, Dunbar RIM (2013) Processing power limits social group size: computational evidence
for the cognitive costs of sociality. Proceedings of the Royal Society B-Biological Sciences 280.
8. David-Barrett T, Dunbar RIM (2014) Social elites can emerge naturally when interaction in networks is
restricted. Behavioral Ecology 25: 5868.
9. Zhou WX, Sornette D, Hill RA, Dunbar RIM (2005) Discrete hierarchical organization of social group
sizes. Proceedings of the Royal Society B-Biological Sciences 272: 439444. PMID: 15734699
10. Hamilton MJ, Milne BT, Walker RS, Burger O, Brown JH (2007) The complex structure of hunter-gath-
erer social networks. Proceedings of the Royal Society B-Biological Sciences 274: 21952202. PMID:
17609186
11. Sutcliffe A, Dunbar R, Binder J, Arrow H (2012) Relationships and the social brain: integrating psycho-
logical and evolutionary perspectives. British Journal of Psychology.
12. Dunbar RIM (2012) Bridging the bonding gap: the transition from primates to humans. Philosophical
Transactions of the Royal Society B.
13. Silk JB, Alberts SC, Altmann J (2006) Social relationships among adult female baboons (Papio cynoce-
phalus) II. Variation in the quality and stability of social bonds. Behavioral Ecology & Sociobiology 61:
197204.
14. Adiseshan A, Adiseshan T, Isbell LA (2011) Affiliative relationships and reciprocity among adult male
bonnet macaques (Macaca radiata) at Arunachala Hill, India. Am J Primatol 73: 11071113. doi: 10.
1002/ajp.20987 PMID: 21905059
15. Seyfarth RM, Cheney DL (2012) The Evolutionary Origins of Friendship. Annual Review of Psychology,
Vol 63 63: 153177. doi: 10.1146/annurev-psych-120710-100337 PMID: 21740224
Women Favour Dyadic Relationships, but Men Prefer Clubs
PLOS ONE | DOI:10.1371/journal.pone.0118329 March 16, 2015 12 / 15
16. Tiger L (1974) Sex-specific friendship. In: Leyton E, editor. The Compact: Selected Dimensions of
Friendship: St John's Memorial University of New Foundland. pp. 4248.
17. Wrangham R (2000) Why are male chimpanzees more gregarious than mothers? A scramble competi-
tion hypothesis. In: Kappeler PM, editor. Primate males: causes and consequences of variation in
group composition Cambridge: University of Cambridge Press. pp. 248258.
18. Benenson JF, Alavi K (2004) Sex differences in children's investment in same-sex peers. Evolution and
Human Behavior 25: 258266.
19. Chapais B (2008) Primeval kinship: how pair-bonding gave birth to human society. Cambridge, Mass.;
London: Harvard University Press. xv, 349 p. p.
20. Geary DC, Byrd-Craven J, Hoard MK, Vigil J, Numtee C (2003) Evolution and development of boys' so-
cial behavior. Developmental Review 23: 444470.
21. Rose AJ, Rudolph KD (2006) A review of sex differences in peer relationship processes: Potential
trade-offs for the emotional and behavioral development of girls and boys. Psychological Bulletin 132:
98131. PMID: 16435959
22. Hall JA (2011) Sex differences in friendship expectations: A meta-analysis. Journal of Social and Per-
sonal Relationships 28: 723747.
23. Baron-Cohen S, Wheelwright S (2003) The friendship questionnaire: An investigation of adults with
Asperger syndrome or high-functioning autism, and normal sex differences. Journal of Autism and De-
velopmental Disorders 33: 509517. PMID: 14594330
24. Vigil JM (2007) Asymmetries in the friendship preferences and social styles of men and women.
Human Nature-an Interdisciplinary Biosocial Perspective 18: 143161.
25. Campbell A (2002) A mind of her own: the evolutionary psychology of women. Oxford: Oxford Univer-
sity Press. 393 p. p.
26. Palchykov V, Kaski K, Kertesz J, Barabasi AL, Dunbar RIM (2012) Sex differences in intimate relation-
ships. Scientific Reports 2.
27. Fehr BA (1996) Friendship processes. Thousand Oaks, Calif; London: Sage. xv, 240 p p.
28. Guyer AE, McClure-Tone EB, Shiffrin ND, Pine DS, Nelson EE (2009) Probing the neural correlates of
anticipated peer evaluation in adolescence. Child Dev 80: 10001015. doi: 10.1111/j.1467-8624.2009.
01313.x PMID: 19630890
29. Benenson JF, Markovits H, Thompson ME, Wrangham RW (2011) Under Threat of Social Exclusion,
Females Exclude More Than Males. Psychological Science 22: 538544. doi: 10.1177/
0956797611402511 PMID: 21403174
30. Benenson JF, Quinn A, Stella S (2012) Boys affiliate more than girls with a familiar same-sex peer.
Journal of Experimental Child Psychology 113: 587593. doi: 10.1016/j.jecp.2012.08.003 PMID:
22981686
31. Fabes RA, Hanish LD, Martin CL (2003) Children at play: The role of peers in understanding the effects
of child care. Child Development 74: 10391043. PMID: 12938698
32. Belle D (1989) Gender differences in children's social networks and supports. In: Belle D, editor. Chil-
dren's social networks and social supports. Oxford, England: John Wiley & Sons.
33. Savin-Williams RC (1980) Friendship and social relations in children In: Foot HC, Chapman AJ, Smith
JR, editors. Social interactions of adolescent females in natural groups. New York: John Wiley. pp.
343364.
34. Langergraber K, Mitani J, Vigilant L (2009) Kinship and social bonds in femalechimpanzees (Pan trog-
lodytes). Am J Primatol 71: 840851. doi: 10.1002/ajp.20711 PMID: 19475543
35. Foley RA, Lee PC (1989) Finite Social Space, Evolutionary Pathways, and Reconstructing Hominid Be-
havior. Science 243: 901906. PMID: 2493158
36. Wrangham RW (1987) The significance of African apes for reconstructing human social evolution. In:
Kinzey WG, editor. Primate Models of Hominid Evolution Albany, New York: SUNY Press.
37. Bruckner E, Knaup K (1993) Womens and Mens Friendships in Comparative Perspective. European
Sociological Review 9: 249266.
38. Sheets VL, Lugar R (2005) Friendship and gender in Russia and the United States. Sex Roles 52:
131140.
39. Roberts SGB, Dunbar RIM, Pollet TV, Kuppens T (2009) Exploring variation in active network size:
Constraints and ego characteristics. Social Networks 31: 138146.
40. Burleson BR (1997) A different voice on different cultures: Illusion and reality in the study of sex differ-
ences in personal relationships. Personal Relationships 4: 229241.
Women Favour Dyadic Relationships, but Men Prefer Clubs
PLOS ONE | DOI:10.1371/journal.pone.0118329 March 16, 2015 13 / 15
41. Oxley NL, Dzindolet MT, Miller JL (2002) Sex differences in communication with close friends: Testing
Tannen's claims. Psychological Reports 91: 537544. PMID: 12416849
42. Rotkirch A, Lyons M, David-Barrett T, Jokela M (2014) Gratitude for help among adult friends and sib-
lings. Evol Psychol 12: 673686. PMID: 25300047
43. Caldwell MA, Peplau LA (1982) Sex-Differences in Same-Sex Friendship. Sex Roles 8: 721732.
44. Duck S, Wright PH (1993) Reexamining Gender Differences in Same-Gender Friendshipsa Close
Look at 2 Kinds of Data. Sex Roles 28: 709727.
45. Benenson JF, Heath A (2006) Boys withdraw more in one-on-one interactions, whereas girls withdraw
more in groups. Developmental Psychology 42: 272282. PMID: 16569166
46. Hruschka DJ (2010) Friendship: development, ecology, and evolution of a relationship. Berkeley,
Calif.; London: University of California Press. xiv, 383 p. p.
47. Henrich J, Heine SJ, Norenzayan A (2010) The weirdest people in the world? Behavioral and Brain Sci-
ences 33: 61+. doi: 10.1017/S0140525X0999152X PMID: 20550733
48. Samter W, Whaley BB, Mortenson ST, Burleson BR (1997) Ethnicity and emotional support in same-
sex friendship: A comparison of Asian-Americans, African-Americans, and Euro-Americans. Personal
Relationships 4: 413430.
49. Ueno K, Adams RG (2006) Adult friendship: A decade review. In: Noller P, Feeney JA, editors. In Close
relationships (functions, forms and processes). New York and Hove: Psychology Press. pp. 151170.
50. Durant KT, McCray AT, Safran C (2012) Identifying gender-preferred communication styles within on-
line cancer communities: a retrospective, longitudinal analysis. PLoS One 7: e49169. doi: 10.1371/
journal.pone.0049169 PMID: 23155460
51. Hum NJ, Chamberlin PE, Hambright BL, Portwood AC, Schat AC, et al. (2011) A picture is worth a thou-
sand words: A content analysis of Facebook profile photographs. Computers in Human Behavior 27:
18281833.
52. Walther JB, Van der Heide B, Kim SY, Westerman D, Tong ST (2008) The role of friends' appearance
and behavior on evaluations of individuals on facebook: Are we known by the company we keep?
Human Communication Research 34: 28U60.
53. Wang SS, Moon SI, Kwon KH, Evans CA, Stefanone MA (2010) Face off: Implications of visual cues on
initiating friendship on Facebook. Computers in Human Behavior 26: 226234.
54. Mendelson AL, Papacharissi Z (2010) Look at us: Collective Narcissism in College Student Facebook
Photo Galleries. In: Papacharissi Z, editor. The Networked Self: Identity, Community and Cultureon So-
cial Network Sites: Routledge.
55. Nadkarni A, Hofmann SG (2012) Why do people use Facebook? Personality and Individual Differences
52: 243249. PMID: 22544987
56. Back MD, Stopfer JM, Vazire S, Gaddis S, Schmukle SC, et al. (2010) Facebook Profiles Reflect Actual
Personality, Not Self-Idealization. Psychological Science 21: 372374. doi: 10.1177/
0956797609360756 PMID: 20424071
57. PewGlobal (2012) Pew Research Global Attitudes Project. http://www.pewglobal.org.
58. Ip GWM, Chiu CY, Wan C (2006) Birds of a feather and birds flocking together: Physical versus behav-
ioral cues may lead to trait- versus goal-based group perception. Journal of Personality and Social Psy-
chology 90: 368381. PMID: 16594825
59. McPherson M, Smith-Lovin L, Cook JM (2001) Birds of a feather: Homophily in social networks. Annual
Review of Sociology 27: 415444.
60. Roberts SGB, Dunbar RIM (2011) The costs of family and friends: An 18-month longitudinal study of re-
lationship maintenance and decay. Evolution and Human Behavior, 32: 186197.
61. Saramaki J, Leicht EA, Lopez E, Roberts SG, Reed-Tsochas F, et al. (2014) Persistence of social sig-
natures in human communication. Proc Natl Acad Sci U S A 111: 942947. doi: 10.1073/pnas.
1308540110 PMID: 24395777
62. Roberts SGB, Dunbar RIM, Pollet TV, Kuppens T (2009) Exploring variation in active network size:
Constraints and ego characteristics. Social Networks 31: 138146.
63. Fortunato L (2011) Reconstructing the History of Residence Strategies in Indo-European-SpeakingSo-
cieties: Neo-, Uxori-, and Virilocality. Human Biology 83: 107128. doi: 10.3378/027.083.0107 PMID:
21453007
64. Seielstad MT, Minch E, Cavalli-Sforza LL (1998) Genetic evidence for a higher female migration rate in
humans. Nature Genetics 20: 278280. PMID: 9806547
65. Silk JB (2007) Social components of fitness in primate groups. Science 317: 13471351. PMID:
17823344
Women Favour Dyadic Relationships, but Men Prefer Clubs
PLOS ONE | DOI:10.1371/journal.pone.0118329 March 16, 2015 14 / 15
66. Silk JB, Beehner JC, Bergman TJ, Crockford C, Engh AL, et al. (2009) The benefits of social capital:
close social bonds among female baboons enhance offspring survival. Proceedings of the Royal Socie-
ty B-Biological Sciences 276: 30993104. doi: 10.1098/rspb.2009.0681 PMID: 19515668
67. Essock-Vitale SM, McGuire MT (1985) Women's lives viewed from an evolutionary perspective. II. Pat-
terns of helping. Ethology and Sociobiology 6.
68. Scelza BA (2011) Female Mobility and Postmarital Kin Access in a Patrilocal Society. Human Nature-
an Interdisciplinary Biosocial Perspective 22: 377393. doi: 10.1007/s12110-011-9125-5 PMID:
22388944
69. Heim P, Murphy S, Golant SK (2003) In the company of women: indirect aggression among women:
why we hurt each other and how to stop. New York: Jeremy P Tarcher/Putnam.
70. Heim P, Murphy S, Golant SK (2001) In the company of women: turning workplace conflict into powerful
alliances. New York: J.P. Tarcher/Putnam. 335 p. p.
71. Furuichi T (2011) Female Contributions to the Peaceful Nature of Bonobo Society. Evolutionary Anthro-
pology 20: 131142. doi: 10.1002/evan.20308 PMID: 22038769
72. Fehr B (2004) Intimacy expectations in same-sex friendships: A prototype interaction-pattern model.
Journal of Personality and Social Psychology 86: 265284. PMID: 14769083
73. Taylor SE, Klein LC, Lewis BP, Gruenewald TL, Gurung RAR, et al. (2000) Biobehavioral responses to
stress in females: Tend-and-befriend, not fight-or-flight. Psychological Review 107: 411429. PMID:
10941275
74. Shultz S, Opie C, Atkinson QD (2011) Stepwise evolution of stable sociality in primates. Nature 479:
219222. doi: 10.1038/nature10601 PMID: 22071768
75. Palchykov V, Kaski K, Kertesz J, Barabasi AL, Dunbar RI (2012) Sex differences in intimate relation-
ships. Sci Rep 2: 370. doi: 10.1038/srep00370 PMID: 22518274
76. de Waal FBM (1984) Sex-Differences in the Formation of Coalitions among Chimpanzees. Ethology
and Sociobiology 5: 239255.
Women Favour Dyadic Relationships, but Men Prefer Clubs
PLOS ONE | DOI:10.1371/journal.pone.0118329 March 16, 2015 15 / 15
... Although sex-gender differences in friendship had been observed in many cultures and settings [48][49][50][51][52][53][54][55][56], the first comprehensive global study took place only less than a decade ago [57]. This study of ~112,000 Facebook profile pictures showed a striking gender difference in both the propensity to create dyadic connections, and the affinity towards large groups, a phenomenon that held across all global regions. ...
... The research assistants were instructed, both verbally on a skype call and in writing (see Supplementary Material 1), to find a coder position in a public space, from which to observe people going about their daily lives, and record their observations on physical copies of a tally sheet (see Supplementary Material 2). The tally sheet was designed to be as similar to the 'profile picture' frequency study's tally sheet [57] The data cleaning took substantial amount of time: most problems were due to the regional and language variation of MS Excel, the software in which most RAs reported their results, as well as due to a few RAs having somewhat redesigned the report sheet. ...
... The 'profile pictures' study had somewhat more women, and the current 'public spaces' study has somewhat more men. To correct for this, I used the approach of the 'profile pictures' paper [57], by employing single person frequencies as inverse weight to the 2F/2M ratio, yielding the adjusted ratio of (2F/1F)/(2M/1M)-1, which is 41.8% in the 'profile pictures' paper and is 49.7% in the current 'public spaces' study. These are not significantly different from each other (Fig. 2). ...
Preprint
Full-text available
One of the most contested questions about human behaviour is whether there are inherent sex or gender differences in the formation and maintenance of social bonds. On one hand, female and male brains are structurally almost identical, and while there are sex differences in the endocrine system, these are small, while much of gendered identity and behaviour is learned. On the other hand, sex differences in some aspects of social behaviour have deep evolutionary roots, and are widely present in non-human animals. This observational study recorded the frequency of same-aged, adult human groups appearing in public spaces through 2636 hours, recording group formation by 1.2mn people via 170 research assistants in 46 countries across the world. The results show (a) a significant sex-gender difference in same-sex-same-age frequency, in that ~50% more female-female than male-male pairs are observed in public spaces globally, and (b) that despite regional variation, the patterns holds up in every global region. This is the first study of sex-gender difference in dyadic social behaviour across the world on this scale, and the first global study that uses direct rather than internet-based observations.
... Further, naturalistic findings with adults show that more extreme forms of within-group competition occur when resources are scarce for both men (Daly & Wilson, 1988) and women (Campbell, 2004). Accordingly, across cultures and age, girls and women interact with fewer samesex peers than males do in less dense configurations David-Barrett, 2022;David-Barrett et al., 2015;Gest et al., 2007;Savin-Williams, 1980), which almost certainly reduces competition. Furthermore, when females do form same-sex friends, they vet them more carefully than males do, ensuring that friends are not competitive. ...
... The basis for the development of girls' and women's same-sex friendships also merits investigation. In contrast to the shared group activities and associated skills and interests that typically underlie boys' and men's same-sex friendships, girls' and women's friendships typically occur with one or two equals who mutually share vulnerabilities and emotional support David-Barrett, 2022;David-Barrett et al., 2015;Rose & Rudolph, 2006;Rudolph & Dodson, 2022;Savin-Williams, 1980;Tesser et al., 1988;Winstead & Griffin, 2001). The purpose of exposing personal vulnerabilities, which can invite victimization, could include Content courtesy of Springer Nature, terms of use apply. ...
Article
Full-text available
Objectives A paradox exists in research on girls and women. On the one hand, they behave in a more egalitarian fashion than their male counterparts. On the other hand, status increases their own and their children’s survival. Methods Evidence from non-human primates can help reconcile these findings. In species that do not reside with female kin for life, females are relatively egalitarian and individualistic. They typically do not cooperate or engage in direct competition and exhibit little tolerance for status differentials. Results and Conclusions Women follow this pattern. While a husband’s status and her female relatives’ support enhance a woman’s status and reproductive success, her own actions too influence her access to resources and allies. Evidence on girls’ and women’s same-sex competition and quests for status supports the hypothesis that human females inhabit dispersal-egalitarian communities in which competition is avoided, an egalitarian ethos prevails, competitive behavior is disguised, and status differentials are not tolerated.
... The standardized regression coefficient is interpreted as the estimated number of standard deviations of change in the dependent variable for one standard deviation unit change in the independent variable, controlling for other independent variables. As MCS and PCS have been shown to be the strongest predictors for MCS and PCS at a later time point [34,35], we have run hierarchical linear regressions with first including MCS and PCS at baseline, and then entering all the other variables of interest as predictors for MCS and PCS three years later. Determination coefficients (R 2 ) were calculated and reported for both models (basic model including only MCS and PCS at baseline vs. full model). ...
... Thus, it can be hypothesized that women are more sensitive regarding feelings of loneliness or social dissonance. In addition, David-Barrett et al. described that women rely more on close one-to-one relationships in comparison with men [35]. In this context, Li et al. [36] revealed that several types of social activities showed weaker associations with HRQOL among women as compared with men. ...
Article
Full-text available
Purpose Health-related quality of life (HRQOL) in older persons is influenced by physical and mental health, as well as by their social contacts and social support. Older women and men have disparate types of social networks; they each value social ties differently and experience loneliness in unique and personal ways. The aim of this study is, therefore, to determine the longitudinal association between loneliness and social isolation with HRQOL in older people—separated by gender. Methods Data stem from the third and fourth follow-up of the ESTHER study—a population-based cohort study of the older population in Germany. A sample of 2171 older women and men (mean age: 69.3 years, range 57–84 years) were included in this study; HRQOL was assessed by using the Short Form-12 questionnaire (SF-12). Data on physical and mental health, loneliness, and social networks were examined in the course of comprehensive home visits by trained study doctors. Gender-specific linear regression analyses were performed to predict physical quality of life (measured by the PCS, physical component score of the SF-12) and mental quality of life (measured by the MCS, mental component score) after three years, adjusted by socioeconomic variables as well as physical, mental, and social well-being. Results At baseline, PCS was 41.3 (SD: 10.0) in women and 42.2 (SD: 9.6) in men ( p = .04). MCS was 47.0 (SD: 10.2) in women and 49.6 (SD: 8.6) in men ( p < .001). In both genders, PCS and MCS were lower three years later. Loneliness at t0 was negatively associated with both PCS and MCS after three years (t1) among women, and with MCS but not PCS after three years among men. In both genders, the strongest predictor of PCS after three years was PCS at t0 ( p < .001), while the strongest predictors of MCS after three years were MCS and PCS at t0. Conclusion HRQOL in elderly women and men is predicted by different biopsychosocial factors. Loneliness predicts decreased MCS after three years in both genders, but decreased PCS after three years only in women. Thus, a greater impact of loneliness on the health of older women can be surmised and should therefore be considered in the context of their medical care.
... Yet there is also evidence that, in addition to their many commonalities, men's and women's friendships possess some sex-differentiated features that might prompt sex differences in friendship jealousy. For example, men's and women's friendship structures often differ, with women preferring extremely close dyadic bonds and men looser multi-male groups (e.g., Benenson, 2014;David-Barrett et al., 2015). Some work suggests that men's and women's same-sex alliances might also have historically served some distinct functions (e.g., Benenson, 2014;Campbell, 2002;Geary, 1998;Reynolds, 2021;Vigil, 2007;Wrangham, 1999). ...
... In terms of sex differences in friendship structures, females tend to form one or two very close dyadic friendships, whereas males tend to form looser multi-male friendship groups. These structural differences are found across cultures and in contexts as disparate as children's play groups and adults' Facebook profile pictures (e.g., Benenson, 2014;Benenson, Apostoleris, & Parnass, 1997;David-Barrett et al., 2015;Kon & Losenkov, 1978). To use the terminology of friendship niches (Tooby & Cosmides, 1996), this implies that women might most commonly have one or two deep niches, whereas men might often have more numerous, shallower niches. ...
Article
Friendships provide material benefits, bolster health, and may help solve adaptive challenges. However, a recurrent obstacle to sustaining those friendships—and thus enjoying many friendship-mediated fitness benefits—is interference from other people. Friendship jealousy may be well-designed for helping both men and women meet the recurrent, adaptive challenge of retaining friends in the face of such third-party interference. Although we thus expect several sex similarities in the general cognitive architecture of friendship jealousy (e.g., it is attuned to friend value), there are also sex differences in friendship structures and historical functions, which might influence the inputs of friendship jealousy (e.g., the value of any one friendship). If so, we should also expect some sex differences in friendship jealousy. Findings from a reanalysis of previously-published data and a new experiment, including both U.S. student and adult community participants (N = 993), provide initial support for three predicted sex differences: women (versus men) report greater friendship jealousy at the prospective loss of best friends to others, men (versus women) report greater friendship jealousy at the prospective loss of acquaintances to others, and men's (but not women's) friendship jealousy is enhanced in the context of intergroup contests.
... However, even though the top five ranks may not be able to take into account the actual support clique of the users, it still provides us with a number of new insights into the dynamics of close relationships formed between the same-gender and opposite-gender individuals. Firstly, the lower ranks of the males in MM friendships when compared to FF friendships strongly suggest that females tend to have more intense friendships than males 32 . In general, the females tend to have fewer and more close relationships than males as can be seen through the comparison of the ranks in Fig. 1. ...
Preprint
Full-text available
Humans are social animals and the interpersonal bonds formed between them are crucial for their development and well being in a society. These relationships are usually structured into several layers (Dunbar's layers of friendship) depending on their significance in an individual's life with closest friends and family being the most important ones taking major part of their time and communication effort. However, we have little idea how the initiation and termination of these relationships occurs across the lifespan. To explore this, we analyse a national cellphone database to determine how and when changes in close relationships occur in the two genders. In general, membership of this inner circle of intimate relationships is extremely stable, at least over a three-year period. However, around 1-4% of alters change every year, with the rate of change being higher among 17-21 year olds than older adults. Young adult females terminate more of their opposite-gender relationships, while older males are more persistent in trying to maintain relationships in decline. These results emphasise the variability in relationship dynamics across age and gender, and remind us that individual differences play an important role in the structure of social networks. Overall, our study provides a holistic understanding of the dynamic nature of relationships during the life-course of humans.
... Essas aparentes diferenças de qualidade-quantidade para as amizades sugerem uma diferença universal e fundamental na função de amizades próximas entre os dois sexos. 26 Neste estudo também foram encontradas relações inversamente proporcionais entre timidez e ansiedade com a competência em comunicação interpessoal, ou seja, estudantes mais tímidos e ansiosos mostraram menos competência frente aos relacionamentos interpessoais. ...
Article
Full-text available
Objectives: to identify the interpersonal communication competence of students in the context of undergraduate Nursing and associate social characteristics and anxiety traits with competence in interpersonal communication. Method: quantitative cross-sectional study carried out with undergraduate Nursing students from two private higher education universities. In this study, three instruments were used: a survey participant characterization questionnaire, the Trait Scale component of the State-Trait Anxiety Inventory (STAI) and the Interpersonal Communication Competence Scale (ICCS). Results: the study sample consisted of 613 students with a mean age of 25.53 (±7.93). The higher the family income, the greater tend to be assertiveness, handling interactions and controlling the environment. The longer the student is in the course, the greater the self-disclosure and control of the environment. Women tend to reveal themselves more and have more availability in interpersonal relationships. Evening students tend to be less available than morning students. The shyer and more anxious student, the less competent will be in interpersonal communication. Conclusions: there is an association between income and assertiveness, managing interactions and controlling the environment; the semester with self-disclosure and control of the environment; of sex with availability and self-disclosure; the period in which the student takes the course and availability. Shyness and anxiety were negative variables in relation to competence in interpersonal communication.
... Evidence that same-sex friendships have historically helped solve some sex-linked challenges is linked to the observation of sex differences in modern friendship structures (see Benenson, 2014;Vigil, 2007). Across cultures, male friendships are typically characterized by larger, less intimate groups, whereas female friendships tend to be dyadic and emotionally close (e.g., Benenson, Apostoleris, & Parnass, 1997;David-Barrett et al., 2015;Kon & Losenkov, 1978). Evolutionary accounts often locate the cause for these structural differences in the historical functions of men's coalitions: For men, other males were often important allies in intergroup conflict (Van Vugt, De Cremer, & Janssen, 2007;Wrangham, 1999). ...
Article
Friendships can help us solve a number of challenges, increasing our welfare and fitness. Across evolutionary time, some of the many challenges that friendships helped to solve may have differed between men and women. By considering the specific and potentially distinct recurrent problems men's and women's friendships helped them solve, we can derive predictions about the qualities that would have made men's and women's same-sex friends ideal partners. This logic leads to several predictions about the specific friend preferences that may be differentially prized by men and women. Across three studies (N = 745) with U.S. participants—assessing ideal hypothetical friends, actual friends, and using a paradigm adapted from behavioral economics—we find that men, compared to women, more highly value same-sex friends who are physically formidable, possess high status, possess wealth, and afford access to potential mates. In contrast, women, compared to men, more highly value friends who provide emotional support, intimacy, and useful social information. Findings suggest that the specific friendship qualities men and women preferred differed by sex in ways consistent with a functional account of friendship.
... Research has also outlined a paradox in women's interpersonal relationships. Women's friendships are more likely to be dyadic (David-Barrett et al., 2015;Winstead, 1986), suggesting that women invest their time and energy in a single friend instead of many friends. But women's friendships are also more fragile and less tolerant to issues within the relationship (Benenson, 2013;Benenson et al., 2009;Benenson & Christakos, 2003), suggesting that women's friendships are also more likely to end. ...
Article
Here, we identify a novel reason why women are often criticized and condemned for (allegedly) sexually permissive behavior due to their choice of clothing. Combining principles from coordinated condemnation and sexual economics theory, we developed a model of competition that helps explain this behavior. We hypothesized that women collectively condemn other women who appear to be sexually permissive (based on their choice of clothing). Study 1 (N = 712) demonstrated that women perceived a rival with visible cleavage more negatively. These perceptions were ultimately driven by the belief that "provocatively" dressed women are more likely to have one-night stands. Study 2 (N = 341) demonstrated that women criticized provocatively dressed women, even when these women were not direct sexual rivals (e.g., her boyfriend's sister). Our findings suggest that future research should investigate competition outside of mating-relevant domains to understand women's intrasexual competition fully.
Preprint
Full-text available
Research on close relationships has tended to focus on the dyad (e.g., friends, romantic partners, rivals). Less attention has been paid to the myriad third parties who impact our social lives through their own relationships with our dyadic partners. What drives our feelings toward such third parties? A classic formalist theory, Balance Theory, suggests we like third parties who share our feelings toward our existing partners (and dislike those who do not) because of affective balance. Here, we propose a new embedded dyad framework which foregrounds the substantive indirect effects that third parties can have on our outcomes through their relationships with our partners. Consistent with the embedded dyad framework, we find that people like third parties who share our hatred for our rivals and our love for our friends (as predicted by both views); but we dislike those who share our love for our spouses (countering Balance Theory). Further supporting predictions uniquely derived from an embedded dyad framework, (a) greater perceived exclusivity in positive dyadic relationships (e.g., friendships) drives dislike toward third parties who share our love for our positive partners; (b) greater perceived welfare suppression by our negative partners (e.g., rivals) drives liking toward third parties who share our hatred of our negative partners. This framework thus critically extends cognitive consistency views by emphasizing the real costs and benefits of navigating dyadic relationships within larger social networks.
Article
We investigate the impact of professional networks on men's and women's earnings, using a dataset of European and North American executives. The size of an individual's network of influential former colleagues has a large positive association with remuneration, with an elasticity of around 21%. However, controlling for unobserved heterogeneity using various fixed effects as well as a placebo technique, we find that the real causal impact of networks is barely positive for men and significantly lower for women. We provide suggestive evidence indicating that the apparent discrimination against women is due to two factors: first, both men and women are helped more by own-gender than other-gender connections, and men have more of these than women do. Second, a subset of employers we identify as ‘female friendly firms’ recruit more women but reward networks less than other firms.
Article
Full-text available
This paper examines social network size in contemporary Western society based on the exchange of Christmas cards. Maximum network size averaged 153.5 individuals, with a mean network size of 124.9 for those individuals explicitly contacted; these values are remarkably close to the group size of 150 predicted for humans on the basis of the size of their neocortex. Age, household type, and the relationship to the individual influence network structure, although the proportion of kin remained relatively constant at around 21%. Frequency of contact between network members was primarily determined by two classes of variable: passive factors (distance, work colleague, overseas) and active factors (emotional closeness, genetic relatedness). Controlling for the influence of passive factors on contact rates allowed the hierarchical structure of human social groups to be delimited. These findings suggest that there may be cognitive constraints on network size.
Article
Full-text available
Animal (and human) societies characterized by dominance hierarchies invariably suffer from inequality. The rise of inequality has 3 main prerequisites: 1) a group in which inequality can emerge, 2) the existence of differences in payoff, and 3) a mechanism that initiates, accumulates, and propagates the differences. Hitherto, 2 kinds of models have been used to study the processes involved. In winner–loser models of inequality (typical in zoology), the 3 elements are independent. In division-of-labor models of inequality, the first 2 elements are linked, whereas the third is independent. In this article, we propose a new model, that of synchronized group action, in which all 3 elements are linked. Under these conditions, agent-based simulations of communal action in multilayered communities naturally give rise to endogenous status, emergent social stratification, and the rise of elite cliques. We show that our 3 emergent social phenomena (status, stratification, and elite formation) react to natural variations in merit (the capacity to influence others’ decisions). We also show that the group-level efficiency and inequality consequences of these emergent phenomena define a space for social institutions that optimize efficiency gain in some fitness-related respect, while controlling the loss of efficiency and equality in other respects.
Article
Full-text available
: Although gratitude is a key prosocial emotion reinforcing reciprocal altruism, it has been largely ignored in the empirical literature. We examined feelings of gratitude and the importance of reciprocity in same-sex peer relations. Participants were 772 individuals (189 males, mean age = 28.80) who filled in an on-line survey using a vignette design. We investigated (i) differences in reported gratitude and importance of reciprocity among same-sex siblings and same-sex friends and (ii) how relationship closeness moderates the associations. Based on the theory of kin altruism we expect that people would feel more grateful towards friends than towards their siblings, and that lack of gratitude or failure to pay back a loan would bother more with friends than with siblings, irrespective of emotional closeness. Results showed that levels of gratitude and expectations of reciprocity were higher towards friends compared to siblings. This was the case also after controlling for emotional closeness. Being close generally made participants feel more grateful and expect lower displays of gratitude in the other. Closeness was also strongly associated with emotional gratitude among siblings compared to friends. We conclude that feelings and displays of gratitude have a special role in friendships. Although a close sibling may elicit as much gratitude as a friend does, even a very close friend is not exempted from the logic of reciprocity in the same way that a sibling is.
Article
Full-text available
The social network maintained by a focal individual, or ego, is intrinsically dynamic and typically exhibits some turnover in membership over time as personal circumstances change. However, the consequences of such changes on the distribution of an ego's network ties are not well understood. Here we use a unique 18-mo dataset that combines mobile phone calls and survey data to track changes in the ego networks and communication patterns of students making the transition from school to university or work. Our analysis reveals that individuals display a distinctive and robust social signature, captured by how interactions are distributed across different alters. Notably, for a given ego, these social signatures tend to persist over time, despite considerable turnover in the identity of alters in the ego network. Thus, as new network members are added, some old network members either are replaced or receive fewer calls, preserving the overall distribution of calls across network members. This is likely to reflect the consequences of finite resources such as the time available for communication, the cognitive and emotional effort required to sustain close relationships, and the ability to make emotional investments.
Article
This paper deals with the question of gender and nation-specific differences in friendship patterns. Analysing quantitative and qualitative aspects of friendship in five nations, it becomes apparent that nation-related variations are greater than gender-specific ones. There seems to be a nation-specific rather than a gender-specific idea of how many people can be friends, who could be a friend, and what friends are for.
Article
Friends-they are generous and cooperative with each other in ways that appear to defy standard evolutionary expectations, frequently sacrificing for one another without concern for past behaviors or future consequences. In this fascinating multidisciplinary study, Daniel J. Hruschka synthesizes an array of cross-cultural, experimental, and ethnographic data to understand the broad meaning of friendship, how it develops, how it interfaces with kinship and romantic relationships, and how it differs from place to place. Hruschka argues that friendship is a special form of reciprocal altruism based not on tit-for-tat accounting or forward-looking rationality, but rather on mutual goodwill that is built up along the way in human relationships.