Behavioral inhibition, heart period, and respiratory sinus arrhythmia in young children.

Children were selected according to criteria for high or low behavioral inhibition (BI) on the basis of both a maternal questionnaire and interviewer ratings at home. Subsequent laboratory assessments involved further BI ratings as well as heart period (HP) and respiratory sinus arrhythmia (RSA). BI, HP, and RSA were all moderately stable from 4.5 to 7 years. HP and RSA changed in meaningful ways according to the context of different laboratory episodes. No significant relations emerged between BI and HP or RSA over the whole sample. However, HP predicted which of the children in the high inhibition group would remain inhibited at 7 years: HP at 4.5 years was significantly lower for children with high BI ratings at 4.5 who remained high at 7 years compared with children with high BI at 4.5 years who were less inhibited at 7 years.