This study examined the interaction of early rearing environment and genetic background on the development of social behaviors in mice. Most research on the effects of early experience on development focuses on the timing and type of early perturbations. To date comparatively little research has focused on the role of genetic variation in how the nervous system interprets a particular type of experience. This study examines how genetic makeup might produce different responses, in adult mice, to early experiences. The study examined the response of several different strains of mice to varying periods of handling. Replicating earlier studies in rats, this experiment showed that animals handled daily for a relatively short period of time as infants show less response to stress as adults, compared to normal animals and animals handled daily for a very long period of time.
These experiments are the first step in laying the groundwork for significant research in the genetic contribution to behavioral differences. Replicating this research in the mouse will allow scientists to conduct similar studies with strains of mice that are known to have distinct genetic patterns underlying specific behavioral traits such as anxiety or heightened reactivity to stress. Such genetic patterns are not yet well established in rats. Knowing the genetic differences in these strains, combined with examining brain differences in animals with different responses to early experiences, will allow scientists to hypothesize about the way experience and genetic makeup interact to produce particular behavioral outcomes.