However, by the time the infants were 12 months old, the pattern changed. Infants with the risk form of the gene who also had mothers who were highly sensitive now showed the expected cardiac response while they were exposed to the stressful situation. Those infants with the risk form of the gene who had insensitive mothers continued to show the ineffective cardiac response to the stressor. These findings suggest that although genes play a role in the development of physiological responses to stress, environmental experience (such as mothers' sensitive care-giving behavior) can have a strong influence, enough to change the effect that genes have on physiology very early in life. The researchers suggest this may be because of the cumulative effect on infants of exposure to their mothers' behavior.
"Our findings provide further support for the notion that the development of complex behavioral and physiological responses is not the result of nature or nurture, but rather a combination of the two," says Cathi Propper, research scientist at the University of North Carolina-Chapel Hill and the study's lead author. "They also illustrate the importance of parenting not just for the development of children's behavior, but for the underlying physiological mechanisms that support this behavior.
"Lastly, infancy is an important time for developing behavioral and biological processes. Although these processes will continue to change over time, parenting can have important positive effects even when children have inherited a genetic vulnerability to problematic behaviors."
|Contact: Andrea Browning|
Society for Research in Child Development