Childhood derivatives of inhibition and lack of inhibition to the unfamiliar.

Behavioral and physiological assessments of 41 7 1/2-year-old children who had been selected to be inhibited or uninhibited at 21 months and observed again at 4 and 5 1/2 years revealed that each of the 2 original behavioral profiles predicted theoretically reasonable derivatives. A majority of the formerly shy, timid children became quiet and socially avoidant in unfamiliar social situations, while a majority of the formerly sociable children became talkative and interactive with peers and adults. Absolute heart-rate and cortisol level at 7 1/2 years were not as discriminating of the 2 behavioral groups as they had been 2 years earlier.