Cardiac Orienting to Pulsed and Continuous Auditory Stimulation: A Developmental Study

Pulsed presentations of auditory stimulation have been shown to be particularly effective in eliciting cardiac deceleration (orienting) during earliest infancy. In the present study the processing of pulsed as compared to continuous stimulation was studied developmentally for two infant age groups (13–18 and 26–35 weeks) and one adult group. Ten habituation trials of either a pulsed or a continuous 10-sec tone were followed by 2 dishabituation trials, in which the temporal pattern (continuous vs pulsed) was shifted. The dishabituation data showed that the two kinds of stimulation were discriminated, but the only finding of differential processing relating to the relevance of pulsed stimulation for younger infants was a tendency for infant subjects, unlike adults, to show prolonged orienting to initial presentations of the pulsed tone. For rate of habituation there were no differential effects. Only in the adult group was the response during dishabituation influenced by the direction of change of temporal pattern. Orienting to stimulus offset was observed on initial presentations of the continuous stimulus for the older infant group.