ABSTRACT
The infant's relativities profile at four months proved to be a sensitive predictor of inhibited and uninhibited behavior in the second year. The implication is that the physiological characteristics of these two behavioral styles should also be present in high and low reactive infants. The high reactive infants also showed higher two-week sleeping heart rates while being held erect by the mother. The mean heart rates gathered at four months and older during quiet baseline periods, when no stress was imposed, did not differentiate high from low reactive infants nor high from low fear children. The analyses deal with heart rate activity when the child was in an alert, nonirritable, and relatively quiescent state. Although high heart rates, resulting from large accelerations in response to the strangers and sour taste, distinguished high from low reactive girls, very low heart rates better discriminated the two groups of boys.
