Mechanisms in auditory discrimination: Ontogeny and phylogeny

Abstract

Previously reported data indicates that human adults, human infants, monkeys, and birds can all be easily trained to discriminate frequency increments, frequency decrements, and intensity increments in a pulsed‐tone stimulus using a repeating standard procedure and operant conditioning techniques. However, it is difficult, if not impossible, to train infants, monkeys, and birds to discriminate intensity decrements using the same methods, although human adults experience no difficulty with this task. An hypothesis to account for these results will be proposed: Discrimination of frequency increments, frequency decrements, and intensity increments implies a coding mechanism based on detecting rate increases in populations of peripheral auditory neurons, but discrimination of intensity decrements implies a mechanism based on detecting rate decreases. Therefore, the CNSs of human infants, monkeys, and birds may not be well adapted to monitoring rate decreases in peripheral auditory neurons. [Supported by Deafn...