How hard can it be to ignore the pan in panda? Effort of lexical competition as measured in pupil dilation

When speech comprehension becomes effortful, e.g. in adverse conditions, it is necessary to understand which processes are the sources of the effort. By means of pupillometry, this paper investigates whether the automatic process of lexical competition increases effort, and whether mismatching cues, degradation of the signal, and listener’ experience with degraded signals additionally affect the effort, as reflected by increased pupil dilation. Listeners’ pupil dilation was measured during the disambiguation of embedded words when presented with cues that either served or hampered disambiguation. Furthermore, listeners were presented with natural or degraded speech. The effect of experience was measured by testing also long-term users of cochlear implants. Lexical competition increased the effort of processing natural speech and even more so for stimuli with mismatching cues. Mere listening to degraded speech increased the effort more than lexical competition. Experience with degraded speech reduced the effort stemming from listening to un-natural speech.