Auditory (dis-)fluency triggers sequential processing adjustments

An increasing amount of studies indicates that experiencing increased task demands, triggered for example by conflicting stimulus features or low perceptual fluency, lead to processing adjustments. While these demand-triggered processing adjustments have been shown for different paradigms (e.g., response conflict tasks, perceptual disfluency, task switching, dual tasking), most of them are restricted to the visual modality. The present study investigated as to whether the challenge to understand speech signals in normal-hearing subjects would also lead to sequential processing adjustments if the processing fluency of the respective auditory signals changes from trial to trial. To that end, we used spoken number words (one to nine) that were either presented with high (clean speech) or low perceptual fluency (i.e., vocoded speech as used in cochlear implants-Experiment 1; speech embedded in multi-speaker babble noise as typically found in bars-Experiment 2). Participants had to judge the spoken number words as smaller or larger than five. Results show that the fluency effect (performance difference between high and low perceptual fluency) in both experiments was smaller following disfluent words. Thus, if it's hard to understand, you try harder.