Frequency discrimination by infants and adults

Abstract

Frequency difference thresholds were estimated for infants (5 to 8 months old) using the visually reinforced head‐turn procedure. Stimuli were 500‐ms tone bursts at six frequencies ranging from 250 to 8000 Hz presented monaurally via a TDH‐49 earphone. Tone bursts were presented at 70 dB above adult absolute threshold. An adaptive threshold estimation procedure with a variable step size was used. An adult group was run using the same protocol. The relative difference threshold (Δf/f) was a nonmonotonic function of frequency with a minimum around 1000 Hz for both age groups. However, infants had higher thresholds than adults at frequencies from 250 to 2000 Hz (approximately 2% for infants versus 1% for adults). No age difference in threshold was observed at 4000 or 8000 Hz. Age differences in absolute sensitivity at low frequencies [Trehub et al., J. Exp. Child Psychol. 21, 219–225] are not great enough to account for the rather large difference in discrimination performance in the low‐frequency range. It is suggested that these findings reflect continuing development of the analytic capacity of the auditory system during the first year of life. [Work supported by Virginia Commonwealth University Faculty Grants‐in‐Aid.]