Neural Representation of Phonetic and Phonemic Categories
My dissertation focuses on the content of auditory memory traces generated in response to varying input sounds. I use the mismatch negativity (MMN) response as an index of prediction (and prediction error) to probe the content of these auditory mental representations. This work is a response to a body of work using the varying standards paradigm to enforce phonological representations (e.g. Phillips et al., 2000). Phillips et al. argue that with varying stimuli, the auditory processing system falls back on phonological representations stored in long-term memory to make active predictions, which leads to an inability to differentiate between within-category tokens. My current study contradicts this by finding a robust MMN effect in a varying standards paradigm to a within-category deviant.
In future experiments, I plan to measure the response to two across-category deviants in order to test for an effect of acoustic distance. If the memory trace of the standards is phonological, it should not contain any acoustic information. If this is the case, the response to both deviants will be identical, despite their differing distance to the standards. If, however, the memory trace is phonetic, the amplitude of the MMN response will be contingent on the deviant’s distance to the standards.
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