title: Mapping the perceptual magnet effect for speech using signal detection theory and multidimensional scaling.
abstract: Recent experiments have demonstrated that the category goodness of speech sounds strongly influences perception in both adult and infants [Kuhl, Percept. Psychophys. 50, 93-107 (1991); Kuhl et al., Science 255, 606-608 (1992)]. Stimuli judged as exceptionally good instances of phonetic categories (prototypes) make neighboring tokens in the vowel space seem more similar, exhibiting a perceptual magnet effect. Three experiments further examined the perceptual magnet effect in adults. Experiment 1 collected goodness and identification judgments for 13 variants of the vowel /i/. Experiment 2 used signal detection theory to assess the discrimination of these tokens using a bias-free measure (d'). Experiment 3 employed multidimensional scaling (MDS) to geometrically model the distortion of the perceptual space due to the magnet effect. The results demonstrated a strong relationship between category goodness and discrimination. Vowel tokens receiving high goodness ratings in experiment 1 were more difficult to discriminate in experiment 2 and were more tightly clustered in the MDS solutions of experiment 3. These findings support the existence of a perceptual magnet effect, and may help explain some aspects of first language learning in infants and second language learning in adults.
authors.affiliation: Department of Speech and Hearing Sciences, University of Washington, Seattle 98195.
authors.forename: P
authors.initials: P
authors.lastname: Iverson
authors.forename: P K
authors.initials: PK
authors.lastname: Kuhl
mesh_terms: D006801:Humans; D010700:Phonetics; D017603:Signal Detection, Psychological; D013063:Speech Discrimination Tests; D013067:Speech Perception