Testing Infants' Discrimination With the Orientation Latency Procedure.

A new discrimination procedure based on the measurement of visual orientation latency to speech stimuli is introduced. Each participant listens to a series of short familiarization test trials. In each trial, 5 to 7 centrally-presented familiarization stimuli are followed by laterally-presented test stimuli. Infants were found to orient faster to different-category than to same-category test stimuli. This result was found despite a high degree of prosodic variability in the familiarization and test stimuli introduced by changes in talker and speaking rate. The combination of a multitrial design with use of acoustic and prosodic variability seems suitable for studying the representation of phonological categories.