Our first examination of G×E interaction involved an effort to understand the effects of early experience on the pathways to externalizing behavior. In these preliminary analyses, 9-month-old infants were observed during a frustration task in which an acrylic glass barrier was placed in front of the infant in a series of six 30-s intervals. For half of the trials, the child could play with an attractive toy (neutral trials); for the other half of the trials, the child could see but not touch the attractive toy (frustration trials). The child's attention during the frustration trials, controlling for his/her attention level during the neutral trials, was hypothesized to serve as an early index of externalizing problems. Prior research has shown that infants who fail to shift attention away from frustrating events, an indication of an inability to adaptively manage frustration, exhibit increased aggressive behavior at age 2-½ years (Crockenberg et al. 2008) and that at-risk children overattend to negative cues (Shackman et al. 2007).
