| Summary: | My Ph.D examines the role of the prototype in speech perception. Although existing research claims that the speech prototype acts as a perceptual attractor for other stimuli in the same speech-sound category, I argue instead that the prototype actually has two roles in the perceptual system - as both a perceptual attractor (i.e. showing reduced discrimination in the surrounding perceptual space) and a perceptual repellor (i.e. showing enhanced discrimination) and that the choice of role depends entirely on the needs of the listener and the needs of the system that he/she is part of. This claim is substantiated through my work on non-speech prototypes in which I found that although professional musicians treat music prototypes as perceptual repellors, non-musicians treat them as perceptual attractors. Because a professional musician 'needs' to be able to recognise how precisely 'in-tune' a musical sound is, enhanced discrimination is needed around their music prototypes. In contrast, a non-musician typically listens to music only to be entertained and can therefore show reduced discrimination around a music prototype. This is true also for the average individual listening to speech who does not 'need' to register how qualitatively good an incoming speech-sound is as long as it is recognisable. Under normal circumstances, therefore, speech-sound prototypes function as perceptual attractors. I believe that the role of the prototype is determined by the amount of attention paid to it by the listener. This has formed the basis for my "A&R Theory" which states that prototypes (in both speech and non-speech) are organised along a perceptual function continuum bounded by regions of minimal and maximal attention, and that the position of the prototype along the continuum at a given point in time is directly dependent on the amount of attention paid to it. At the point of maximal attention (i.e. the professional musician) the prototype acts as a perceptual repellor. At the point of minimal attention (i.e. the non-musician, average listener), the prototype acts as a perceptual attractor. Support for this theory comes from experiments showing that that the position of the prototype along the perceptual function continuum can shift when the attention of the listener is deliberately manipulated. A&R Theory has formed the basis for my model of speech perception development called the Prototype Conversion Model which claims that infants' speech-sound prototypes are initially repellors since infants are able to focus most of their attention onto the sounds of speech, but that these repellors gradually convert to attractors when the infants' attention is distracted by higher-order linguistic functions such as learning their first words. Other work on prototypes in this dissertation has argued that prototypes are highly context-sensitive and that they do not depend initially on exposure to a native language, as has often been claimed in the literature.
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