Publications Related to Lab Projects
Two experiments investigated the mechanism by which listeners adjust their interpretation of accented speech that is similar to a regional dialect of American English. Only a subset of the vowels of English (the front vowels) were shifted during adaptation, which consisted of listening to a 20-min segment of the "Wizard of Oz." Compared to a baseline (unadapted) condition, listeners showed significant adaptation to the accented speech, as indexed by increased word judgments on a lexical decision task. Adaptation also generalized to test words that had not been presented in the accented passage but that contained the shifted vowels. A control experiment showed that the adaptation effect was specific to the direction of the shift in the vowel space and not to a general relaxation of the criterion for what constitutes a good exemplar of the accented vowel category. Taken together, these results provide evidence for a context-specific vowel adaptation mechanism that enables a listener to adjust to the dialect of a particular talker.
In this paper we discuss the role of contrastive features in phoneme acquisition. We conducted an experiment in which participants were presented with an artificial language containing a potential phoneme contrast (e.g. /d/~/D/). They were then tested on an analogous pair of stimuli not presented during training (e.g. /g/~/G/). Training did not generalize to the untrained stimuli, indicating that mere exposure to one example of a featural contrast is insufficient for generalization of that feature to new examples of the contrast. These results demonstrate that language learners do not come to the task with the assumption that they will encounter symmetrical featural systems. We conclude by presenting testable hypotheses to account for how the featural system of a language might be learned.
The present study investigates the effect of the statistical distribution of phonetic variation in the speech signal on listeners’ ability to discriminate a pair of speech sounds. We presented adult subjects with speech sound stimuli exemplifying a phonetic contrast that might potentially be used phonemically in some foreign language. The speech stimuli were resynthesized from natural speech into a phonetic continuum. During the familiarization phase of the experiment, subjects passively listened to the continuum stimuli. Subjects were randomly assigned to one of two familiarization conditions: in the bimodal condition, stimuli near the endpoints of the continuum were presented most frequently; in the unimodal condition, stimuli from the center of the continuum were presented most frequently. Subjects were then given a modified AX discrimination task in which they were tested on their discrimination of the endpoint stimuli. The bimodal group displayed greater discrimination than the unimodal group, demonstrating that brief, passive exposure to a phonetic distribution affects adults' discrimination of speech sounds.
