On the nature of talker variability effects on recall of spoken word lists.

Abstract

In a recent study, Martin, Mullennix, Pisoni, and Summers (1989) reported that subjects' accuracy in recalling lists of spoken words was better for words in early list positions when the words were spoken by a single talker than when they were spoken by multiple talkers. The present study was conducted to examine the nature of these effects in further detail. Accuracy of serial-ordered recall was examined for lists of words spoken by either a single talker or by multiple talkers. Half the lists contained easily recognizable words, and half contained more difficult words, according to a combined metric of word frequency, lexical neighborhood density, and neighborhood frequency. Rate of presentation was manipulated to assess the effects of both variables on rehearsal and perceptual encoding. A strong interaction was obtained between talker variability and rate of presentation. Recall of multiple-talker lists was affected much more than single-talker lists by changes in presentation rate. At slow presentation rates, words in early serial positions produced by multiple talkers were actually recalled more accurately than words produced by a single talker. No interaction was observed for word confusability and rate of presentation. The data provide support for the proposal that talker variability affects the accuracy of recall of spoken words not only by increasing the processing demands for early perceptual encoding of the words, but also by affecting the efficiency of the rehearsal process itself.The perception of spoken language is a skill that requires the listener to extract stable linguistic content from a physical signal that is notoriously unstable. The acoustic realization of speech is simultaneously modulated by numerous variable phonetic, prosodic, and semantic characteristics inherent to the particular message. The speech signal is further modulated by variable source characteristics. Indeed, it has frequently been suggested that if the perceptual system is required to extract canonical units of meaning from spoken language, various idiosyncracies related to different talkers must be somehow "normalized" during an early stage of processing the sensory input (e.g., Joos, 1948). Such talker-specific sources of variability include differing individual dialects, vocal tract sizes and shapes, and speaking rates (Mullennix, Pisoni, & Martin 1988;Verbrugge, Strange, Shankweiler, & Edman, 1976).Sources of variability in speech, whether from phonetic context, spoken stress, or talker variations, have typically been considered "perceptual problems" to be solved by listeners, just as they must be solved for the design of adequate speech-recognition systems (e.g., Gerstman, 1968;. Although the communicative importance of talker-specific information has long been recognized (e.g., Ladefoged & Broadbent, 1957), only recently have questions regarding the encoding of talker-specific information been considered alongside questions regarding the perception of the phonetic content of speech. By assessing the effects ...

Perceptual learning for speech: Is there a return to normal?

“…We argue that phonemic representations are dynamic and flexible, and incorporate specific information about the speech, and the speaker, that a listener is exposed to. This finding ties to the more general literature on perceptual memory for voices (Goldinger, Pisoni, & Logan, 1991;Mullinex & Pisoni, 1990;Nygaard & Pisoni, 1998), which finds that memory for speakers appears to aid perception and interpretation of the speech signal, and argues that speech perception and word recognition models need to incorporate partner specific voice information (see Goldinger, 1998, for a model which does this). This body of work provides interesting evidence that speakers are important to listeners, and it supports the idea that information about partners may well be a basic part of ordinary memory representations, and not incorporated at some later extralinguistic processing stage.…”

Episodic encoding of voice attributes and recognition memory for spoken words.

“…Recall of items in the primacy portion of the lists was reduced by introducing talker variability; recall of items from the middle or end of the list was not affected. These results were replicated in later studies (Goldinger, Pisoni, & Logan, 1991;Lightfoot, 1989;Logan & Pisoni, 1987).…”

Toward an integrative model of talker normalization.

“…This indicates that exemplars of words stored in memory preserved a talker's voice information implicitly. Altogether, these findings suggest that a learned talker's voice characteristics can be stored in memory (e.g., Craik & Kirsner, 1974;Goldinger, 1991;1996;1998;Hintzman et al, 1972;Johnson, 1997;2007;Palmeri et al, 1993). Based on the above discussion, we speculate that a space of learned talker models, i.e., voice characteristics of previously encountered talkers and maybe exemplars of speech sounds from those talkers, is stored in the memory of listeners.…”