Discrimination of sound localization cues in young infants.

Infants 8 and 16 weeks old were tested in a visual fixation paradigm for the detection and use of sound localization cues. The effects of changes in both interaural intensity and interaural arrival time were assessed independently. For each trial, sounds were presented at the same time as visual displays located on both sides of the infant. The first eye movement and total looking time to each of the visual displays were noted by corneal reflection. Following a series of trials in which the apparent location of the sound was on 1 side, the apparent location was changed for a series of test trials. Neither age group responded with appropriate directional eye movements. The older infants did, however, show generally increased looking time on the test trials for both binaural cues. The 8-week-olds responded on test trials only when the interaural arrival time was changed. The data indicate that both binaural cues can be detected by 16-week-old infants although interaural arrival time was more salient in this paradigm.