Memory modes and perceptual anchors in categorical perception

Abstract

A theory of intensity perception developed by Durlach and Braida [J. Acoust. Sac. Am. 46, 372–383 (1969), et seq.] is applied to data from categorical perception experiments. According to the theory, two memory modes are used in processing perceptual continua. In the trace mode, observers compare stimuli with the memory traces of other stimuli, and performance is limited by the inter‐stimulus interval. In the context mode, observers compare stimuli to perceptual anchors, and performance is limited by the stimulus range. Analysis of existing speech and nonspeech data reveals that stimulus domains differ in (a) the amount of trace variance, (b) the amount of context‐coding variance, and (c) the existence and location of anchors; but no single parameter captures the categorical/continuous distinction. Memory variances and anchor locations can be estimated from experiments in which fixed‐level discrimination, as well as identification and roving‐level discrimination, is measured. Among the few experiments with categorically perceived continua that have used the critical fixed‐level condition are some in which discrimination peaks arise from anchors, and others in which they reflect regions of high basic sensitivity. [Work supported by NIH.]