Modality differences in the habituation and dishabituation of cardiac responsiveness in the human newborn.

The relative efficacy of (1) repeated auditory and somesthetic stimulation for the habituation of cardiac acceleration responses and (2) intramodal and cross-modal stimulation for the dishabituation of cardiac responses was studied in 45 full-term 2-day-old infants. Although the stimuli were equally effective initially, repeated presentation of the somesthetic stimulus had a greater decremental effect than repeated presentation of the auditory stimulus. The stimuli were equally effective in producing dishabituation when in a different modality from that of the habituating stimulus (cross-modal) but not when in the same modality (intramodal). Changes in the locus of stimulation without a change in modality were ineffective for producing dishabituation. The findings indicate the human newborn discriminates auditory and somesthetic inputs effectively and equally but does not discriminate contralateral from ipsilateral stimulation in either modality.