A CASE-STUDY OF PERCEPTUAL AND ACOUSTIC FEATURES OF AN INFANTS 1ST LAUGH UTTERANCES

Twenty-four consecutive utterances produced by a 21-week-old infant during a peek-a-boo activity were recorded and randomly presented to 46 adults who rated each utterance using a 7-point scale varying from laugh to cry. Three judges identified the occurrence of five acoustic features in each utterance (syllabic vocalizations, hard attacks, glottal stops, vocalized inhalations, and duration). Perceptual judgments of these variables were verified using acoustic intensity tracings from a Visi-Pitch analyzer. Five of the nine utterances that more than 70% of listeners agreed were laugh responses consisted of a series of two syllabic vocalizations produced in rapid succession (the second vocalization terminated by a glottal stop) followed by a rapid vocalized inhalation. Utterances that were perceived by more than 70% of the listeners as non-laugh or unclassified utterances usually contained only one syllabic vocalization (with one exception) and no hard attacks, glottal stops or vocalized inhalations. Duration of the utterance was not a significant factor that discriminated laugh from non-laugh utterances. © 1994, Walter de Gruyter. All rights reserved.