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Yerkes Researchers Find Sex Differences in Monkey Toy Preferences Similar to Humans

April 10, 2008

Nonhuman primate-based behavioral studies suggest hormones may shape preferences

Media Contacts

Emily Rios, 404-727-7732, erios@emory.edu; Lisa Newbern, 404-727-7709, lisa.newbern@emory.edu

ATLANTA – Researchers at the Yerkes National Primate Research Center, Emory University, have found rhesus monkeys’ gender-specific toy preferences directly parallel the preferences human children have, suggesting preferences can develop without socialization factors, such as encouragement from family and friends to play with gender-specific toys. The study, now available in the online edition of Hormones and Behavior, proposes sex differences in toy preferences reflect hormonally influenced behavioral and cognitive biases.

Yerkes lead researcher Janice Hassett said, “Sex differences in human toy preferences are often thought to occur primarily through socialization influences, such as parents encouraging sons to play with cars and trucks and daughters to play with dolls and stuffed animals. If, however, preferences for gender specific toys exist in other species, then nonsocial factors also may play a role in preference.”

Yerkes researchers compared the interactions of 11 male and 23 female rhesus macaques with human wheeled toys (masculine) and plush toys (feminine). Like young boys, male monkeys strongly preferred wheeled toys, while female monkeys, similar to young girls, played more equally with both types of toys. “Young girls show a broader range of play patterns than boys, playing with many different kinds of toys,” said Hassett. “We found this to be true with the female monkeys as well. This suggests that rather than specific socialization determining toy preferences, it’s more likely biases in preferences that exist at birth” continued Hassett.

“We were quite surprised by how closely the preferences of male and female monkeys for human gender-stereotyped toys paralleled those reported in children,” said Kim Wallen, PhD, study co-author. “Because monkeys are not subjected to advertisements, or to criticism for toy choice, this suggests the monkeys choose the toys on the basis of the activities the toys encourage. Thus, differences in activity preference vary between males and females,” Wallen summarized.

These results may be applied to other sex differences. Hassett offered, “Traditional thinking is sex differences, such as career choice and performance on specific types of cognitive tests, are a result of socialization – labeling professions as masculine or feminine and teaching boys and girls differently. While this almost certainly occurs, it is possible our early preferences shape our environment such that later in life men and women seek different activities and ways of spending time and resources.”

For more than seven decades, the Yerkes National Primate Research Center, Emory University, has been dedicated to conducting essential basic science and translational research to advance scientific understanding and to improve the health and well-being of humans and nonhuman primates. Today, the center, as one of only eight National Institutes of Health–funded national primate research centers, provides leadership, training and resources to foster scientific creativity, collaboration and discoveries. Yerkes-based research is grounded in scientific integrity, expert knowledge, respect for colleagues, an open exchange of ideas and compassionate, quality animal care.

Within the fields of microbiology and immunology, neuroscience, psychobiology and sensory-motor systems, the center’s research programs are seeking ways to: develop vaccines for infectious and noninfectious diseases, such as AIDS and Alzheimer’s disease; treat cocaine addiction; interpret brain activity through imaging; increase understanding of progressive illnesses such as Parkinson’s and Alzheimer’s; unlock the secrets of memory; determine behavioral effects of hormone replacement therapy; address vision disorders; and advance knowledge about the evolutionary
links between biology and behavior.



The Robert W. Woodruff Health Sciences Center of Emory University is an academic health science and service center focused on missions of teaching, research, health care and public service. Its components include the Emory University School of Medicine, Nell Hodgson Woodruff School of Nursing, and Rollins School of Public Health; Yerkes National Primate Research Center; Winship Cancer Institute of Emory University; and Emory Healthcare, the largest, most comprehensive health system in Georgia. Emory Healthcare includes: The Emory Clinic, Emory-Children's Center, Emory University Hospital, Emory University Hospital Midtown, Wesley Woods Center, and Emory University Orthopaedics & Spine Hospital. The Woodruff Health Sciences Center has a $2.5 billion budget, 17,600 employees, 2,500 full-time and 1,500 affiliated faculty, 4,700 students and trainees, and a $5.7 billion economic impact on metro Atlanta.

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