Hormones and Behavior 54 (2008) 359–364

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Sex differences in rhesus monkey toy preferences parallel those of children
Janice M. Hassett a,b,c, Erin R. Siebert b, Kim Wallen a,b,c,⁎ a b c Department of Psychology, Emory University, Atlanta, GA 30322, USA
Yerkes National Primate Research Center, Atlanta, GA 30322, USA
Center for Behavioral Neuroscience, Atlanta, GA, 30322, USA

a r t i c l e

i n f o

Article history:
Received 10 January 2008
Revised 14 March 2008
Accepted 14 March 2008
Available online 25 March 2008
Keywords:
Sex differences
Toy preference
Gender
Hormones
Rhesus monkey
Children
Socialization

a b s t r a c t
Sex differences in toy preferences in children are marked, with boys expressing stronger and more rigid toy preferences than girls, whose preferences are more flexible. Socialization processes, parents, or peers encouraging play with gender-specific toys are thought to be the primary force shaping sex differences in toy preference. A contrast in view is that toy preferences reflect biologically-determined preferences for specific activities facilitated by specific toys. Sex differences in juvenile activities, such as rough-and-tumble play, peer preferences, and infant interest, share similarities in humans and monkeys. Thus if activity preferences shape toy preferences, male and female monkeys may show toy preferences similar to those seen in boys and girls.
We compared the interactions of 34 rhesus monkeys, living within a 135 monkey troop, with human wheeled toys and plush toys. Male monkeys, like boys, showed consistent and strong preferences for wheeled toys, while female monkeys, like girls, showed greater variability in preferences. Thus, the magnitude of preference for wheeled over plush toys differed significantly between males and females. The similarities to human findings demonstrate that such preferences can develop without explicit gendered socialization. We offer the hypothesis that toy preferences reflect hormonally influenced behavioral and cognitive biases which are sculpted by social processes into the sex differences seen in monkeys and humans.
© 2008 Elsevier Inc. All rights reserved.

Toy play is one of the most robust human behavioral sex differences, showing moderate to very large effect sizes (Cohen-Bendahan et al.,
2005; Collaer and Hines, 1995). As seen in Fig. 1A, boys interact more with masculine-type toys than do girls, and girls interact more with feminine-type toys than do boys (Berenbaum and Hines, 1992). Within each sex, boys typically show strong preferences for stereotypically masculine toys, while girls often do not show a statistically greater preference for one toy type over another (Berenbaum and Hines, 1992;
Carter and Levy, 1988; Eisenberg and Wolchik, 1985; Frasher et al., 1980;
Perry et al.,1984; Sutton-Smith and Rosenberg,1963; Turner et al.,1993).
Thus sex differences in toy preferences are characterized by stronger gender-specific preferences in boys than in girls.
Socialization processes have typically been offered as the primary source of the sex differences in human toy preferences. While there are many hypothesized socialization mechanisms (Bandura and Bussey,
2004; Martin and Halverson, 1981; Martin et al., 2002), one view is that societal endorsement of toys as masculine or feminine drive children's toy preferences to conform to expected masculine and feminine gender roles (Martin and Little, 1990). Some have suggested that a greater preference for gendered toys in boys reflects a greater rejection of opposite-sex behavior in boys than in girls (Bussey and Perry, 1982).
Thus, girls are less rigid than boys in their gender-typed beliefs, behaviors, and preferences, including toy preferences (Ruble et al., 2006).
⁎ Corresponding author. Emory University Department of Psychology, Atlanta, GA
30322, USA. Fax: +1 404