Multidimensional scaling and perceptual features: Reflections of stimulus processing or long‐term memory prototypes?

Abstract

Many researchers have obtained information on phonetic perception by using various multidimensional scaling (MDS) procedures to discover underlying perceptual dimensions. Such dimensions are usually characterized in terms of the acoustic characteristics of the stimuli and have been interpreted as representing factors used to identify vowel (or consonant) quality in phonetic perception. However, several studies suggest that such dimensions may reflect properties of the vowel's long‐term memory prototype rather than the actual acoustic nature of the stimuli. For example, MDS studies commonly find no features reflecting dynamic acoustic information [e.g., R. Fox, Lang. Speech 26, 21–60 (1983)] and one study [B. Rakerd, J. Acout. Soc. Am. Suppl. 1 73, S54 (1983)] found that similar perceptual features were extracted when Ss either heard or imagined remembered) stimulus tokens. To investigate this issue an experiment was designed to determine the extent to which slight acoustic variation in a subset of the synthetic vowels presented to Ss for scaling would produce differences in perceived perceptual distance estimates. Results suggest that Ss are sensitive to relatively small acoustic differences while making dyadic comparisons even when there is no concomitant phonemic quality variation or specific instructions expect such variations. It will be argued that such results suggest that MDS procedures do tap lower‐level perceptual processes and do not merely reflect long‐term memory prototypes.