Cardiac reactivity is associated with changes in negative emotion in 24-month-olds.

Despite the call for multilevel observation of negative affect, including multiple physiological systems, too little empirical research has been conducted in infants and young children, and physiology-affect associations are not consistently reported. We examined changes in heart rate, respiratory sinus arrhythmia, and preejection period in 24-month-olds across four increasingly challenging, emotion-eliciting tasks. We predicted that changes in cardiac reactivity would be systematically related to changes in negative affect. Results largely support the predictions with one important exception. With increasing distress across the tasks, HR increased and RSA decreased. However, no significant changes in PEP were observed. HR was associated with negative affect during all tasks, and changes in HR were related to changes in negative affect. PEP and negative affect were associated, but only marginally so. Within-subject analyses confirmed the predicted associations. Finally, the associations between physiology and negative affect were different for boys and girls. We discuss these results in the context of implications for future research on cardiac-affect associations in young children. Copyright (c) 2005 Wiley Periodicals, Inc.