For research on emotional development, defining emotions as psychological systems of appraisals, expressions, body reactions, and subjective feelings in all phases of ontogenesis raises tricky methodological issues. How can we measure single emotions when appraisals and feelings cannot be assessed from outside, when expressions do not seem to be…

Among 36 newborns, Infant Behavior Questionnaire (IBQ) activity level, responsivity, and irritability exhibited stability from 2 weeks to 2 months and from 2 months to 12 months. Irritability was stable from 2 weeks to 12 months. IBQ ratings generally increased by year's end. (RH)

Data suggest that infants with high vagal tone were more reactive than infants with low vagal tone to positive and negative events at 5 months, and were more sociable at 14 months. Infant reactivity to mildly stressful events seemed to be a stable dimension during the first year. (RH)

The predictive relation between neonatal behavior and temperament at 24 months was examined for 67 infants selected from the full socioeconomic status (SES) distribution. Initial ratings were made when the infants were one to four days old. Irritable neonates were rated as more upset, less attentive to stimuli, and less responsive to the staff at…