Evaluating the Sources and Functions of Gradiency in Phoneme Categorization: An Individual Differences Approach

• Published in: Journal of experimental psychology. Human perception and performance 2017-09, Vol.43 (9), p.1594-1611
• Main Authors: Kapnoula, Efthymia C, Winn, Matthew B, Kong, Eun Jong, Edwards, Jan, McMurray, Bob
• Format: Article
• Language: English
• Subjects: Acoustic phonetics; Adult; Classification; Classification (Cognitive Process); Cognition; Cognitive ability; Communication Disorders; Comprehension; Cues; Differences; Dyslexia; Executive Function; Executive Function - physiology; Human; Humans; Individual Differences; Individuality; Inhibition, Psychological; Integration; Language; Language disorders; Listeners; Listening comprehension; Memory, Short-Term - physiology; Noise; Phonemes; Phonetics; Psycholinguistics - methods; Specific Language Impairment; Speech Perception; Speech Perception - physiology; Spoken language; Validity; Verbal communication; Verbal Comprehension; Young Adult
• ISSN: 0096-1523; 1939-1277
• DOI: 10.1037/xhp0000410

During spoken language comprehension listeners transform continuous acoustic cues into categories (e.g., /b/ and /p/). While long-standing research suggests that phonetic categories are activated in a gradient way, there are also clear individual differences in that more gradient categorization has been linked to various communication impairments such as dyslexia and specific language impairments (Joanisse, Manis, Keating, & Seidenberg, 2000; López-Zamora, Luque, Álvarez, & Cobos, 2012; Serniclaes, Van Heghe, Mousty, Carré, & Sprenger-Charolles, 2004; Werker & Tees, 1987). Crucially, most studies have used 2-alternative forced choice (2AFC) tasks to measure the sharpness of between-category boundaries. Here we propose an alternative paradigm that allows us to measure categorization gradiency in a more direct way. Furthermore, we follow an individual differences approach to (a) link this measure of gradiency to multiple cue integration, (b) explore its relationship to a set of other cognitive processes, and (c) evaluate its role in individuals' ability to perceive speech in noise. Our results provide validation for this new method of assessing phoneme categorization gradiency and offer preliminary insights into how different aspects of speech perception may be linked to each other and to more general cognitive processes. Public Significance Statement Labeling sounds and images is an essential part of many cognitive processes that allow us to function efficiently in our everyday lives. One such example is phoneme categorization, which refers to listeners' ability to correctly identify speech sounds (e.g., /b/) and is required for understanding spoken language. The present study presents a novel method for studying differences among listeners in how they categorize speech sounds. Our results show that (a) there is substantial variability among individuals in how they categorize speech sounds, and (b) this variability likely reflects fundamental differences in how listeners use the speech signal. The study of such differences will lead to a more comprehensive understanding of both typical and atypical patterns of language processing. Therefore, in addition to its theoretical significance, this study can also help us advance the ways in which we remediate behaviors linked to atypical perception of speech.