Effects of Stimulus Variability on the Representation of Spoken Words in Memory

Author: Lynne C. Nygaard, Mitchell S. Sommers and David B. Pisoni

Abstract:
The present paper reports a series of experiments designed to investigate the effects of three sources of stimulus variability on the memory representations for spoken words. The aim was to determine if variability in speaking rate and overall amplitude have consequences for the encoding and processing of spoken words and if these consequences are comparable to those found for talker variability. A serial recall task was used to study the effects of changes in speaking rate, talker variability, and amplitude on the initial encoding, rehearsal, and recall of lists of spoken words. Presentation rate was manipulated to determine the time course and nature of processing. The results indicate that at fast presentation rates, variations in both speaking rate and talker characteristics incur a processing cost which influences the initial encoding and subsequent rehearsal of spoken words. At slower presentation rates, however, variation in talker results in improved recall in initial list positions while variation in speaking rate has no effect on recall performance. Amplitude variability had no effect on serial recall at any presentation rate. These results suggest that the encoding of stimulus variability due to changes in speaking rate, talker differences, and amplitude may be the result of distinct perceptual operations.