The aim of our research is to understand sex differences in behaviour in human beings and other animals. We examine how exposure to gonadal hormones during early life influences the developmental trajectory of males and females, how social factors impact upon sex differences in behaviour and cognition, and how evolutionary theory can shed light on sex differences in human behaviour. Our methodologies include behavioural neuroendocrinology, human experimental studies and statistical techniques.
Gonadal hormones and sex differences in behavioural development
During adolescence, circulating levels of gonadal hormones, such as testosterone and estrogen, rise dramatically, and these hormones can have long-term effects on brain development . Our studies of adolescent rats (Rattus norvegicus) have shown that sex differences in behaviour emerge during this stage of life  and that manipulating gonadal hormone levels during adolescence impacts upon the development of behaviour, such as responses to novel objects  and social partners . Our future research will focus both on the adolescent and prenatal periods of life, with the aim of shedding light on sex differences in susceptibility to mental health disorders.
 Brown G & Spencer K. 2013. Neurosci 249, 115-28.  Lynn D & Brown G. 2009. Dev Psychobiol 51, 513-20.  Cyrenne D & Brown G. 2011. Horm Behav 60, 625-31.  Brown G, Kulbarsh K, Spencer K & Duval C. 2015. Horm Behav 73, 135-41.
Sex differences in cognition, confidence and risk-taking
When men and women differ in their average performance on cognitive tasks, the difference is often attributed to ‘ability’. However, factors such as confidence and willingness to take risks can influence learning strategies in such tasks. We have shown that the decision to learn socially, rather than asocially, is influenced both by confidence  and by the riskiness of the social and asocial options . Adolescent girls interpret ambiguous scenarios more negatively than do same-aged boys , and men score higher on average than women on their willingness to experience in novel, intense sensations . Such differences could impact upon sex differences in cognitive tasks.
 Cross C, Brown G, Morgan T & Laland K. 2017. Brit J Psychol 108, 655-667.  Brand C, Brown G & Cross C. 2018. PeerJ 6, e4190.  Brown G, Gluck R & Dritschel B. 2014. Brit J Dev Psychol 32, 116-22.  Cross C, Cyrenne D & Brown. 2013. Sci Rep 3, 2486.
Evolutionary perspectives on sex differences in human behaviour
I have argued that evolutionary accounts of sex differences in human behaviour are often been based on over-simplified or out-dated views of how humans have evolved . In a book co-authored with Kevin Laland (Biology, St Andrews), I have critically evaluated how evolutionary theory has been applied to human behaviour from Darwin to the present day , and we have proposed that a niche construction perspective can provide a richer and fuller account of human behaviour . I am particularly interested in how evolutionary accounts can shed light on the diversity of human behaviour  and the variation both between and within the sexes.
 Brown G, Laland K & Borgerhoff Mulder M. 2009. TREE 24, 297-304.  Laland K & Brown G. 2011. Sense and Nonsense: Evolutionary Perspectives on Human Behaviour, 2nd Ed. OUP.  Laland K & Brown G. 2006. Evol Anthropol 15, 95-104.  Brown G, Dickins T, Sear R & Laland K. 2011. Phil Trans R Soc B 366, 313-24.
Food sharing and social learning in nonhuman primates
In many species of nonhuman primates, young animals will take food items that have been foraged by their parents or other group members . These ‘food transfers’ provide youngsters with an important source of nutrition but can also help them to learn what to eat, where to forage and how to process food . While growing evidence shows that, in several taxonomic groups, knowledgeable individuals ‘teach’ naïve others , our observational studies of family groups of common marmosets showed that the parents did not preferentially share novel items, rather than familiar items, and instead simply responded to patterns of begging behaviour from their offspring .
 Rapaport L & Brown G. 2008. Evol Anthropol 17: 189-201.  Brown G, Almond R & van Bergen Y. 2004. Adv Stud Behav 34, 265-95.  Hoppitt W, Brown G, et al. 2008. TREE 23, 486-93.  Brown G, Almond R & Bates, N. 2005. Am J Primatol 65, 301-12.
Sex-biased parental investment and birth sex ratios in nonhuman primates
Selection is predicted to favour mothers that bias their investment towards sons or daughters when the expected returns are greater for one sex than the other . Joan Silk (ASU) and I evaluated the evidence that the birth sex ratios of nonhuman primates vary according to maternal social rank, with our meta-analyses providing no evidence for biased birth sex ratios . Similarly, our analyses of data from free-ranging baboons failed to find any evidence that birth sex ratios varied with maternal rank . However, our comparative analyses across primate species did reveal evidence that birth sex ratios varied according to which sex disperses from the natal area .
 Brown G. 2001. Anim Behav 61, 683-94.  Brown G & Silk J. 2002. Proc Nat Acad Sci 99, 11252-55.  Silk J, Willoughby E & Brown G. 2005. Proc R Soc B 272, 859-64.  Silk J & Brown G. 2008. Proc R Soc B 275, 1761-65.