Some experiments on perceptual learning of mirror-image acoustic patterns

Abstract

It is well known that the formant transitions of stop consonants in CV and VC syllables are roughly the mirror image of each other in time. These formant motions reflect the acoustic correlates of the articulators as they move rapidly into and out of the period of stop closure. Although acoustically different, these formant transitions are correlated perceptually with similar phonetic segments. Earlier research of Klatt and Shattuck (1975) had suggested that mirror image acoustic patterns resembling formant transitions were not perceived as similar. However, mirror image patterns could still have some underlying similarity which might facilitate learning, recognition, and the establishment of perceptual constancy of phonetic segments across syllable positions. This paper reports the results of four experiments designed to study the perceptual similarity of mirror-image acoustic patterns resembling the formant transitions and steady-state segments of the CV and VC syllables/ba/,/da/,/ab/, and /ad/. Using a perceptual learning paradigm, we found that subjects could learn to assign mirror-image acoustic patterns to arbitrary response categories more consistently than they could do so with similar arrangements of the same patterns based on spectrotemporal commonalities. Subjects respond not only to the individual components or dimensions of these acoustic patterns, but also process entire patterns and make use of the patterns’ internal organization in learning to categorize them consistently according to different classification rules.

Figure 1

Schematic spectrographic patterns of the nonspeech stimuli used in Experiment 1.

Figure 2

Percent correct performance pooled across subjects and individual learning trials for each stimulus set. The data are displayed separately for each response-mapping (i.e., categorization) condition.

Figure 3

Percent correct performance for individual stimuli under the three mapping (i.e., categorization) conditions of the experiment.

Figure 4

Percent correct identification in the labeling task for acoustic and phonetic labels. The data are shown separately for single-, double-, and triple-tone stimuli.

Figure 5

Percent correct identification for individual stimuli in the labeling task shown separately for acoustic and phonetic instruction conditions.

Figure 6

Distribution of responses obtained in the similarity judgment task for the two stimulus sets used in Experiment 4.