Some consequences of stimulus variability on speech processing by 2-month-old infants

Abstract

The present study explores how stimulus variability in speech production influences the 2-monthold infant's perception and memory for speech sounds. Experiment 1 focuses on the consequences of talker variability for the infant's ability to detect differences between speech sounds. When tested with high-amplitude sucking (HAS) procedure, infants who listened to versions of a syllable, such as /b∧g/, produced by 6 male and 6 female talkers, detected a change to another syllable, such as /d∧g/, uttered by the same group of talkers. In fact, infants exposed to multiple talkers performed as well as other infants who heard utterances produced by only a single talker. Moreover, other results showed that infants discriminate the voices of the individual talkers, although discriminating one mixed group of talkers (3 males and 3 females) from another is too difficult for them. Experiment 2 explored the consequences of talker variability on infants' memory for speech sounds. The HAS procedure was modified by introducing a 2-min delay period between the familiarization and test phases of the experiment. Talker variability impeded infants' encoding of speech sounds. Infants who heard versions of the same syllable produced by 12 different talkers did not detect a change to a new syllable produced by the same talkers after the delay period. However, infants who heard the same syllable produced by a single talker were able to detect the phonetic change after the delay. Finally, although infants who heard productions from a single talker retained information about the phonetic structure of the syllable during the delay, they apparently did not retain information about the identity of the talker. Experiment 3 reduced the range of variability across talkers and investigated whether variability interferes with retention of all speech information. Although reducing the range of variability did not lead to retention of phonetic details, infants did recognize a change in the gender of the talkers' voices (from male to female or vice versa) after a 2-min delay. Two additional experiments explored the consequences of limiting the variability to a single talker. In Experiment 4, with an immediate testing procedure, infants exposed to 12 different tokens of one syllable produced by the same talker discriminated

Common Neural Basis for Phoneme Processing in Infants and Adults

“…Like adults, infants perceive phonemes categorically along acoustic dimensions such as voice onset time (VOT) (Eimas, Siqueland, Jusczyk, & Vigorito, 1971), place of articulation (Werker, Gilbert, Humphrey, & Tees, 1981), and others. They are able to normalize across irrelevant acoustic variations such as those related to different voices or pitches ( Jusczyk, Pisoni, & Mullennix, 1992;Kuhl, 1983), or coarticulation context (Bertoncini, Bijeljac-Babic, Jusczyk, Kennedy, & Mehler, 1988). They display duplex perception (Eimas & Miller, 1992).…”

The development of auditory attention in children

“…They can discriminate syllables, even when the tokens of a particular stimulus come from different talkers. This generalization is not based on an inability to differentiate talkers; infants can also discriminate talkers when the syllable remains constant (14,70 (71). In addition, 7-montholds can discriminate sentences with different structures in an artificial language, even when the nonsense words in the test sentences are novel (72).…”

Infants' Recognition of the Sound Patterns of Their Own Names

“…It is well established that within the first 2 months of life, infants are able to discriminate a wide range of speech contrasts (Eimas, Siqueland, Jusczyk, & Vigorito, 1971;Trehub, 1976). Moreover, they appear to be able to compensate for stimulus variability introduced into speech by changes in speaking rate (Eimas & Miller, 1980) and talkers' voices (Jusczyk, Pisoni, & Mullennix, 1992;Kuhl, 1979). These early abilities allow infants to begin the process of categorizing the information available in speech and ultimately lead to acquisition of a native language.…”