Effects of stimulus variability on perception and representation of spoken words in memory

Abstract

A series of experiments was conducted to investigate the effects of stimulus variability on the memory representations for spoken words. A serial recall task was used to study the effects of changes in speaking rate, talker variability, and overall amplitude on the initial encoding, rehearsal, and recall oflists of spoken words. Interstimulus interval (lSI) was manipulated to determine the time course and nature of processing. The results indicated that at short ISis,variations in both talker and speaking rate imposed a processing cost that was reflected in poorer serial recall for the primacy portion of word lists. At longer ISis, however, variation in talker characteristics resulted in improved recall in initial list positions, whereas variation in speaking rate had no effect on recall performance. Amplitude variability had no effect on serial recall across all ISIs. Taken together, these results suggest that encoding of stimulus dimensions such as talker characteristics, speaking rate, and overall amplitude may be the result of distinct perceptual operations. The effects of these sources of stimulus variability in speech are discussed with regard to perceptual saliency, processing demands, and memory representation for spoken words.

Effects of talker, rate, and amplitude variation on recognition memory for spoken words

“…Rather, at the slow presentation rate, there was no difference between recall of items in the multiple-and single-rate lists. Furthermore, Nygaard et al (1995) found no differences between serial recall of single-and multipleamplitude lists at fast or at slow presentation rates. Taken together, these results suggest again that distinctive talker information is encoded in the long-term memory representation of spoken words, and if given sufficient rehearsal time, this additional distinctive information can be used as a retrieval cue by the listener.…”

“…Their study compared the effects of speaking rate and overall amplitude on serial recall with the effects of talker variability. Nygaard et al (1995) found that at fast presentation rates, items presented early in lists spoken either by a single talker or at a single speaking rate were better recalled than the same items spoken by multiple talkers or at multiple speaking rates. At a slow presentation rate, however, early items in the multiple-talker lists were better recalled than those in the single-talker lists; however, this reversal of recall accuracy was not obtained for the items in the multiple-rate lists relative to those in the single-rate lists.…”

“…Some clues to the retention of surface form other than talker's voice come from an earlier study conducted by Nygaard et al (1995). Their study compared the effects of speaking rate and overall amplitude on serial recall with the effects of talker variability.…”

“…To determine whether perceptual effects of stimulus variation are due to time-consuming normalization processes or due to the increased encoding time for perceptual detail, other studies have investigated the effects of stimulus variability on memory for spoken words (e.g., Goldinger et al, 1991;Martin, Mullennix, Pisoni, & Summers, 1989;Nygaard, Sommers, & Pisoni, 1995;Palmeri, Goldinger, & Pisoni, 1993; for reviews, see Pisoni, 1993Pisoni, , 1997. The idea is that if these perceptual effects are due to a normalization process, then memory for spoken words should be based on abstract symbolic linguistic representations.…”

A new method for eliciting three speaking styles in the laboratory

“…The perception of variability that exists among speech styles has not been studied in detail, no doubt due to the problem of eliciting naturalistic speech in the decidedly unnatural manner and the setting of reading aloud in a laboratory, although these issues have begun to be addressed in computer/machine word recognition (Ostendorf, Byrne, Bacchiani, Finke, Gunawardana, Ross, Roweis, Shriberg, Talkin, Waibel, Wheatley, & Zeppenfeld, 1996;Schriberg, 2001;Liu, Shriberg, Stolcke, Hillard, Ostendorf, & Harper, 2006;Bates, Ostendorf, & Wright, 2007). Other types of "nonlinguistic" variability have been shown to have an effect on speech perception and spoken word recognition, including talker, rate, and stimulus variability (Mullennix & Pisoni, 1990;Nygaard, Sommers, & Pisoni, 1995;Bradlow, Nygaard, & Pisoni, 1999). These studies suggest that listeners encode in longterm memory significant episodic details and properties of speech signals that they encounter, and that these details influence the subsequent perception and recognition of speech.…”