There may be a biological basis for separate doll and dump-truck aisles in the toy store.
In a study of baby mice, researchers at 菠萝视频 and the University of Southern California found that males and females respond differently to the hormone arginine-vasopressin (AVP), which plays an important role in social behavior.
The study, published online last December in the journal Hormones and Behavior, found that baby girl mice tend to move toward familiar odors if they previously had smelled that odor near their mothers. Baby boy mice didn鈥檛 seem to be influenced by the odors.
Baby girl mice missing a gene that codes for a receptor known as vasopressin 1a (V1aR), which binds AVP, were especially drawn to familiar odors. Loss of the gene did not change male behavior. Conversely, baby girl mice that had the gene seemed to lose interest in the odors鈥攋ust like the males鈥攊f they were given an extra dose of AVP.
This implies that a rise in AVP levels early in life, which can result from genetic differences or stress or exposure to hormones in the diet, 鈥渕ight lower the probability of orienting toward things associated with mom or home,鈥� says , first author of the study and instructor in pediatrics at 菠萝视频.
Hammock is also a investigator. Her research program focuses on understanding the genes, neural circuits and developmental trajectories that lead to typical and disordered social behavior and emotion regulation. She uses rodent model systems to dissect genes and circuits during postnatal development, with an interest in the mechanisms by which stress and social experience may alter typical trajectories.
Hammock says she is motivated to pursue these questions in order to broaden our knowledge about development of the social brain. Such knowledge should facilitate the creation of more effective intervention strategies used to promote better outcomes in individuals with atypical development such as autism and schizophrenia.
Her findings suggest that AVP, which is more abundant in male brains, may reinforce the tendency of male mice to leave home to establish a new territory elsewhere, a phenomenon known as 鈥渘atal dispersal.鈥�
The hormone may also play a role in social learning. AVP and its receptor, V1aR, previously have been linked to neurodevelopmental disorders such as schizophrenia and autism.
鈥淭hroughout early life, repeated exposure to individuals, experiences and things are required to build a brain with knowledge about the world,鈥� Hammock says. 鈥淚f AVP reduces the probability of orienting to things associated with the center of one鈥檚 social world, then that reduces the exposure required to enhance social expertise.鈥� This might help explain why, on average, women have more social expertise than men and are better able to 鈥渞ead鈥� emotions in others, she says.
During early development, male and female brains may be 鈥渨ired鈥� to experience the world differently. This could help explain why鈥攊n humans and some species of monkeys鈥攇irls gravitate toward dolls that replicate the family and home environment, while boys can be captivated by dump trucks, for example.
Hammock鈥檚 co-authors were former 菠萝视频 research assistant Caitlin Law and Pat Levitt of the Zilkha Neurogenetic Institute at USC鈥檚 Keck School of Medicine. The research was supported by National Institutes of Health grants.