INFANT AUDITORY TEMPORAL ACUITY - GAP DETECTION

The development of auditory temporal acuity during infancy was examined in 3-, 6-, and 12-month-old infants and in adults using the gap detection paradigm. Listeners detected a series of gaps, or silent intervals, of variable duration in a broadband noise. In order to vary the acoustic frequencies available to the listner, a high-pass noise was used to mask frequencies above specified cutoffs. High-pass maskers with cutoffs of 500, 2,000, and 8,000 Hz were used. The minimum detectable gap was determined using the Observer-based Psychoacoustic Procedure. The thresholds of 3- and 6-month-olds were considerably poorer than those of the adults, although the effect of masker condition was about the same for these 3 groups. The thresholds of 12-month-olds were significantly worse than the adults when the stimulus was unmasked or when the masker cutoff frequency was 2,000 or 8,000 Hz. When the masker cutoff frequency was 500 Hz, 12-month-olds fell into 2 groups: some had gap thresholds that were about the same as 3- and 6-month-olds, while some had gap thresholds that approached those of adults. In a second experiment, a larger group of 12-month-olds were tested with a 500-Hz masker cutoff. Average performance of 12-month-olds was about the same as that of 3- and 6-month-olds in Experiment 1. Some infants attained thresholds close to those of adults. Thus, gap detection thresholds are quite poor in infants, although the similarity of the effect of frequency on performance in infants and adults suggests that the mechanisms governing temporal resolution in infants operate qualitatively like those in adults.