Repeatedly experiencing the McGurk effect induces long-lasting changes in auditory speech perception

In the McGurk effect, presentation of incongruent auditory and visual
speech evokes a fusion percept different than either component modality.
We show that repeatedly experiencing the McGurk effect for 14 days induces
a change in auditory-only speech perception: the auditory component of the
McGurk stimulus begins to evoke the fusion percept, even when presented on
its own without accompanying visual speech. This perceptual change, termed
fusion-induced recalibration (FIR), was talker-specific and
syllable-specific and persisted for a year or more in some participants
without any additional McGurk exposure. Participants who did not
experience the McGurk effect did not experience FIR, showing that
recalibration was driven by multisensory prediction error. A causal
inference model of speech perception incorporating multisensory cue
conflict accurately predicted individual differences in FIR. Just as the
McGurk effect demonstrates that visual speech can alter the perception of
auditory speech, FIR shows that these alterations can persist for months
or years. The ability to induce seemingly permanent changes in auditory
speech perception will be useful for studying plasticity in brain networks
for language and may provide new strategies for improving language
learning.