Internal structure of voicing categories in early infancy

Abstract

It is well established that young infants process speech in terms of perceptual categories that closely correspond to the phonetic categories of adult language users. Recently, Kuhl (1991) has provided evidence that this correspondence is not limited to the region of category boundaries: At least by 6-7 months of age, vowel categories of infants, like those of adults, have an internal perceptual structure. In the current experiments, which focused on a consonantal contrast, we found evidence of internally structured categories in even younger infants-3-4 months of age. The implications of these findings for the nature ofthe infant's earliest language-universal categories are discussed, as is the role of exposure to the native language in shaping these categories over the course of development.One of the fundamental issues in speech perception is how listeners map the continuously varying signal of speech onto the phonetic categories of their language. Much of the research on phonetic categorization over the years has focused on the boundaries between phonetic categories, addressing such issues as why boundaries fall where they do along given acoustic continua, what kinds ofcontextual factors playa role in determining boundary location, and the effects of specific linguistic experience in altering boundary location over the course of development (see, e.g., Repp & Liberman, 1987). This emphasis on boundaries derived in part from the much-studied phenomenon of categorical perception, which emphasized the relative difficulty experienced by listeners in discriminating members of a given phonetic category compared with the ease in discriminating tokens that cross a category boundary (Repp, 1984;Studdert-Kennedy, Liberman, Harris, & Cooper, 1970).It has become increasingly clear, however, that phonetic categories are much richer in form than this emphasis on boundaries would suggest. It is now known that listeners can discriminate stimuli from a given category with a relatively high degree of accuracy, given specific stimulus and task conditions (Carney, Widin, & Viemeister, 1977;Samuel, 1977; see also Macmillan, Goldberg, & Braida, 1988). Moreover, and of particular relevance for the current research, there is a growing literature indicating that phonetic categories have a graded internal struc-

Contextual influences on the internal structure of phonetic categories: A distinction between lexical status and speaking rate

“…For a discussion of the ontogeny of internal category structure from various perspectives, see Kluender (1994), Kuhl (2000), and Miller and Eimas (1996).…”

Asymmetries in vowel perception

“…A subsequent study by Polka and Bohn (1996) provided a direct test of this hypothesis that perceptual asymmetries in infant vowel perception are due to the relatively more familiar vowels acting as 1 It should be noted that perceptual asymmetries have also been discussed by Miller and Eimas (1996) with respect to the perception of voicing categories. perceptual magnets.…”

Perceptual reference points for form and orientation in young infants: Anchors or magnets?

“…An anchor effect is present when there is increased discriminability and presumed expansion of the psychological space around the reference point, whereas a magnet effect is present when there is decreased discriminability and presumed shrinkage of psychological space around the reference point. Fourth, and consistent with a magnet effect, reference points may display asymmetries in similarity judgment and discrimination tasks (Krumhansl, 1978(Krumhansl, , 1979Miller & Eimas, 1996;Rosch, 1975;Tversky, 1977). Specifically, higher similarity (and lower discriminability) are in evidence when the reference point stimulus is the standard and the nonreference point stimulus is the comparison than when the converse is true.'…”

“…The present report is concerned with the ontogeny of reference points-in particular, with whether reference points arise because of inherent biases in our perceptual and memory systems that may, in turn, allow for rapid learning of certain classes of information (see Walton & Bower, 1993). Evidence from phonetic categories indicates an early (i.e., prelinguistic) functional onset for reference points in the domain of speech (Kuhl, 1991;Miller & Eimas, 1996), but whether this is the case for categories in the domain of vision remains to be determined. The dimensions of form and orientation were chosen for investigation because ofevidence that ( I) reference points function in these domains for adults (Pomerantz, 1977;Rosch, 1975;Sebrechts & Garner, 1981) and (2) young infants develop category representations for simple geometric form classes and vertical and oblique orientations (reviewed in Quinn & Eimas, 1986), thereby allowing one to establish whether reference points serve as magnets or anchors within their respective classes.…”