  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.
