Phonological (un)certainty weights lexical activation

TL;DR

This study investigates how spoken word recognition in the brain is influenced by phonological certainty and lexical frequency, revealing a dynamic weighting process during word processing.

Contribution

It introduces a neural model demonstrating the changing influence of phonological certainty and frequency on lexical activation during speech recognition.

Findings

Early in word processing, lexical activation is influenced by phonological certainty and frequency.

Later in processing, lexical activation depends primarily on lexical frequency.

Neural responses in auditory cortex reflect these dynamic weighting mechanisms.

Abstract

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.