Heart rate-defined phases of attention, look duration, and infant performance in the paired-comparison paradigm.

Four-month-old infants (N = 68) were tested in a paired-comparison familiarization-novelty recognition task in which the length of choice trials was systematically manipulated. Peak look duration during pretest and familiarization periods significantly predicted a dichotomous measure of recognition performance, but recognition was unaffected by choice-trial length. Heart rate (HR) was simultaneously assessed during the task, and the amount of time infants spent in various HR-defined phases of attention was assessed. Longer durations of looking during pretest and familiarization were significantly associated with more time spent in both sustained attention (SA) and attention termination (AT). Of these two variables, only individual differences in AT accounted for significant variance in recognition memory performance. A final analysis addressed the possibility that individual differences in AT mediated the relation between look duration and recognition performance. These findings provide support for the hypothesis that individual differences in the disengagement of attention underlie the relation between look duration and cognitive performance in early to midinfancy.