Abstract
Auditory intensity difference limens were measured in 40 human infants (ages 7–9 months) and several adults using a go, no—go operant head‐turning technique and an adaptive staircase (tracking) discrimination procedure. Subjects were visually reinforced for responding to intensity increments in a repeating background signal either a 1.0‐kHz tone or a vowel /a/, presented free‐field at a level of 60 dB SPL. Stimulus control in infants was monitored through the use of randomly interleaved “probe” and “catch” trials. Infant thresholds ranged from 3.0 to 12.0 dB for tones and from 2.5 to 12.0 dB for vowels, with the most sensitive infants falling within the range of adults. It is noteworthy that we were unsuccessful in training any infants to respond to intensity decrements, although adults experienced no difficulty with this task. [Supported by NIH grant HD 11915.]
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