Speech Perception Theoretical approaches Scope of the problem Speech perception involves the mapping of speech acoustic signals onto linguistic messages e g phonemes distinctive features syllables words phrases Why is the problem theoretically hard to solve Acoustic variability due to context talker dialect rate prosodic and other differences Segmentation problems Three theoretical approaches Motor theory Direct realism General approach Motor theory of speech perception Liberman Mattingly 1985 Listeners perceive gestures more specifically intended gestures or neuromotor commands Speech is perceived in humans by means of a specialized speech module How the speech module works the candidate signal descriptions are computed by an analogue of the production process an internal innately specified vocal tract synthesizer that incorporates complete information about the anatomical and physiological characteristics of the vocal tract and also about the articulatory and acoustic consequences of linguistically significant gestures Liberman Mattingly 1985 p 26 Spectrograms of di and du Direct realist theory of speech perception C Fowler Derived from James J Gibson s perceptual theory Objects of speech perception are actual gestures No special mechanisms are required How direct realism works Perceptual systems have a universal function They constitute the sole means by which animals can know their niches Moreover they appear to serve this function in one way They use structure in the media that has been lawfully caused by events in the environment as information for the events Even though it is the structure in media light for vision skin for touch air for hearing that sense organs transduce it is not the structure in those media that animals perceive Rather essentially for their survival they perceive the components of their niche that caused the structure Fowler 1996 p 1732 General approach to speech perception Diehl Lotto Holt 2004 Objects of speech perception are primarily acoustic auditory events Speech perception relies on general mechanisms of audition and perceptual learning Variation in VOT Spectrograms of English ba and pa VOT frequency histograms of voicing categories across six languages Lisker Abramson 1964 English identification functions for VOT stimuli superimposed on VOT frequency histograms English discrimination functions for VOT stimuli Thai identification functions for VOT stimuli superimposed on Thai VOT frequency histograms Thai discrimination functions for VOT stimuli Tone onset time TOT a nonspeech analog of Voice onset time VOT Pisoni 1977 Holt Lotto Diehl 2004 50 TOT Frequenc y Hz 50 ms 0 TOT Time ms 50 TOT 50 ms Discrimination functions for TOT stimuli Holt Lotto Diehl 2004 VOT identification by chinchillas Kuhl Miller 1981 ga ka identification by typically developing children and dyslexic children with and without ADHD Back to the three approaches to speech perception Motor theory Direct realism General approach
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