Vocal suppression as a neonatal response to auditory stimuli.

Medically normal neonates in a hospital were tested (mn age: 37.5 hrs old) under two prestimulus states, calm and crying. One group of 15 Ss was randomly assigned to a condition in which a 4-min tape of a woman's voice at 80 db SPL was presented. The other group of 15 Ss was presented with a tape of random noise for 4 min. There were 4-min control tests in each state with no stimulus presentation. Two observers independently timed crying episodes. In the calm state, there was no difference within the speech group between the speech and the control conditions; however, the random-noise group cried significantly less during the noise than in the control. In the crying state, both groups cried significantly less during the stimulus than in the control, noise being significantly superior as a suppressor. There is the possibility that neonates suppress reflexive crying in the presence of an auditory stimulus the better to listen. This possibility may be useful in some phase of screening neonatal hearing sensitivity.