EFFECTS OF STIMULUS VARIABILITY ON PERCEPTION AND REPRESENTATION OF SPOKEN WORDS IN MEMORY

A series of experiments was conducted to investigate the effects of st imulus variability on the memory representations for spoken words. A s erial recall task was used to study the effects of changes in speaking rate, talker variability, and overall amplitude on the initial encodi ng, rehearsal, and recall of lists of spoken words. Interstimulus inte rval (ISI) was manipulated to determine the time course and nature of processing. The results indicated that at short ISIs, variations in ba th talker and speaking rate imposed a processing cost that was reflect ed in poorer serial recall for the primacy portion of word lists. At l onger ISIs, however, variation in talker characteristics resulted in i mproved recall in initial list positions, whereas variation in speakin g rate had no effect on recall performance. Amplitude variability had no effect on serial recall across all ISIs. Taken together these resul ts suggest that encoding of stimulus dimensions such as talker charact eristics, speaking rate, and overall amplitude may be the result of di stinct perceptual operations. The effects of these sources of stimulus variability in speech are discussed with regard to perceptual salienc y, processing demands, and memory representation for spoken words.