Holt_Lotto_2006 - Cue weighting in auditory categorization:...

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Unformatted text preview: Cue weighting in auditory categorization: Implications for first and second language acquisition a) Lori L. Holt b ! Department of Psychology and the Center for the Neural Basis of Cognition, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213 Andrew J. Lotto Center for Perceptual Systems University of Texas at Austin, Austin, Texas 78712 s Received 22 April 2005; revised 14 February 2006; accepted 28 February 2006 d The ability to integrate and weight information across dimensions is central to perception and is particularly important for speech categorization. The present experiments investigate cue weighting by training participants to categorize sounds drawn from a two-dimensional acoustic space defined by the center frequency s CF d and modulation frequency s MF d of frequency-modulated sine waves. These dimensions were psychophysically matched to be equally discriminable and, in the first experiment, were equally informative for accurate categorization. Nevertheless, listeners category responses reflected a bias for use of CF. This bias remained even when the informativeness of CF was decreased by shifting distributions to create more overlap in CF. A reversal of weighting s MF over CF d was obtained when distribution variance was increased for CF. These results demonstrate that even when equally informative and discriminable, acoustic cues are not necessarily equally weighted in categorization; listeners exhibit biases when integrating multiple acoustic dimensions. Moreover, changes in weighting strategies can be affected by changes in input distribution parameters. This methodology provides potential insights into acquisition of speech sound categories, particularly second language categories. One implication is that ineffective cue weighting strategies for phonetic categories may be alleviated by manipulating variance of uninformative dimensions in training stimuli. 2006 Acoustical Society of America. f DOI: 10.1121/1.2188377 g PACS number s s d : 43.71.An, 43.66.Ba, 43.71.Hw f ALF g Pages: 30593071 I. INTRODUCTION Outside of the acoustic researchers laboratory, few sound categories are distinguished by a single acoustic di- mension. In the natural world, auditory categories more typi- cally are defined along multiple dimensions. Integration of information across acoustic dimensions, then, must be a cen- tral characteristic of auditory processing. Speech categories provide an excellent illustration of both the complexity with which multiple acoustic dimen- sions define auditory categories and of the adeptness of the auditory system at integrating information across multiple dimensions. For speech categories, rarely is a single acoustic dimension necessary or sufficient to define category mem- bership; this is the essence of the classic lack of invariance issue s Liberman, 1996; Liberman et al. , 1967 d . For example, there are many acoustic dimensions that contribute to voic- ing, as in the difference between English /ba/ and /pa/; Lisker...
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This note was uploaded on 10/22/2011 for the course LIN 4930 taught by Professor Habib,r during the Spring '08 term at University of Florida.

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Holt_Lotto_2006 - Cue weighting in auditory categorization:...

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