Phonological input processing is reduced during speech planning in turn taking

In conversational turn taking, speech planning and language comprehension are known to frequently overlap in time, which has previously been found to lead to less efficient speech production due to parallel processing of linguistic input. Four experiments were conducted to investigate whether comprehension processes are also impaired by concurrent speech planning, or whether language comprehension is prioritised during process overlap in turn taking. In Experiment 1a, participants verbally responded to quiz questions while monitoring the auditorily presented question for a target phoneme. Phoneme detection performance was found to be reduced when the target phoneme was located at a position in the question where participants were already planning their response as compared to when they were not yet planning their response. A comparison with participants’ phoneme detection performance in Experiments 1b and 1c, featuring either no or a delayed speech planning task, shows that interlocutors prioritise speech planning in phases of limited processing capacity during turn taking situations. In Experiment 2, participants answered the same quiz questions used in Experiment 1a but had to detect tones instead of phonemes. A comparison with the phoneme detection performance in Experiment 1a suggests that speech planning interferes with phonological input processing in particular. Whether domain-general, non-linguistic auditory detection abilities are hindered by concurrent speech planning, as well as the social and processing-related causes and consequences of the common conversational strategy of planning during comprehension are discussed. • Question answerers plan their response before question offset, if possible. • Phoneme monitoring performance is reduced during speech planning. • Speech planning is prioritised during phases of scarce processing resources. • Systematics of turn taking require shallow comprehension at turn transitions.