Effects of cognitive load on speech recognition

The effect of cognitive load (CL) on speech recognition has received little attention despite the prevalence of CL in everyday life, e.g., dual-tasking. To assess the effect of CL on the interaction between lexically-mediated and acoustically-mediated processes, we measured the magnitude of the “Ganong effect” (i.e., lexical bias on phoneme identification) under CL and no CL. CL consisted of a concurrent visual search task. Experiment 1 showed an increased Ganong effect under CL. A time-course analysis of this pattern (Experiments 2 and 3) revealed that the Ganong effect decreased over time under optimal conditions, but it did not under CL. Thus, CL appears to be delaying (and perhaps preventing) listeners’ ability to rely on fine phonetic detail to perform the sub-lexical task. This finding, along with an absence of measurable effects at the post-lexical level (Experiment 4) or at the lexical level (Experiment 5) and a clear negative effect of CL on perceptual discrimination (Experiment 6), suggests that the increased reliance on lexically-mediated processes under CL is the cascaded effect of impoverished encoding of the sensory input. Ways of implementing a link between CL and sensory analysis into existing models of speech recognition are proposed.

► Listeners increase their reliance on lexical knowledge under cognitive load.
► This effect is the cascaded consequence of impoverished sensory encoding.
► It is not the result of an increase in lexical activity per se.