Who speaks next? Adaptations to speaker identity in processing spoken sentences

When listening to a speaker, we need to adapt to her individual speaking characteristics, such as error proneness, accent, etc. The present study investigated two aspects of adaptation to speaker identity during processing spoken sentences in multi-speaker situations: the effect of speaker sequence across sentences and the effect of learning speaker-specific error probability. Spoken sentences were presented, cued, and accompanied by one of three portraits that were labeled as the speakers' faces. In Block 1 speaker-specific probabilities of syntax errors were 10%, 50%, or 90%; in Block 2 they were uniformly 50%. In both blocks, speech errors elicited P600 effects in the scalp recorded ERP. We found a speaker sequence effect only in Block 1: the P600 to target words was larger after speaker switches than after speaker repetitions, independent of sentence correctness. In Block 1, listeners showed higher accuracy in judging sentence correctness spoken by speakers with lower error proportions. No speaker-specific differences in target word P600 and accuracy were found in Block 2. When speakers differ in error proneness, listeners seem to flexibly adapt their speech processing for the upcoming sentence through attention reorientation and resource reallocation if the speaker is about to change, and through proactive maintenance of neural resources if the speaker remains the same.