Infant Heart-Rate Responses to Temporally Predictable and Unpredictable Events

This study assessed the ability of young infants to anticipate the arrival of temporally cued events. Sixteen 7-month-olds and 16 adult subjects were presented with 17 trials in which, 10 s after onset of a white noise (S1), an age-appropriate, interesting event (S2) occurred. On 3 additional trials, distributed throughout the S1-S2 paired trials, reaction to omission of the S2 was assessed. During S1-S2 intervals, anticipatory responses developed after about 12 trials, when both infants and adults produced similar heart-rate decelerations that reached a nadir just as S2 was to arrive. The infant subjects also demonstrated S1-S2 associativity during S2 omission trials; response to S2 omission changed in form over trials from general to temporally precise. These results demonstrate infants' anticipatory abilities and their sensitivity to disruption of experimentally established temporal sequences.