Phonological (un)certainty weights lexical activation
This research addresses a fundamental problem in cognitive neuroscience for understanding speech perception mechanisms, though it is incremental in refining existing models.
The study investigated how uncertainty in phonological categorization and lexical frequency influence spoken word recognition, finding that early in word processing both factors weight lexical activation, but later only frequency matters.
Spoken word recognition involves at least two basic computations. First is matching acoustic input to phonological categories (e.g. /b/, /p/, /d/). Second is activating words consistent with those phonological categories. Here we test the hypothesis that the listener's probability distribution over lexical items is weighted by the outcome of both computations: uncertainty about phonological discretisation and the frequency of the selected word(s). To test this, we record neural responses in auditory cortex using magnetoencephalography, and model this activity as a function of the size and relative activation of lexical candidates. Our findings indicate that towards the beginning of a word, the processing system indeed weights lexical candidates by both phonological certainty and lexical frequency; however, later into the word, activation is weighted by frequency alone.