Johanne Nedergaard, Aarhus University
Joshua Charles Skewes, Aarhus University
Mikkel Wallentin, Aarhus University
Is inner speech involved in sustaining attention, and is this reflected in response times for stimulus detection? In Experiment 1, we measured response times for infrequently occurring stimulus (a black dot occurring at 1–3-minute intervals) and subsequently asked participants to report on the character of inner experience at the time the stimulus appeared. Our main preregistered hypothesis was that there would be an interaction between inner speech and task relevance of thought with reaction times being the fastest on prompts preceded by task-relevant inner speech. This would indicate that participants used their inner voice for attentional control. Participants reported to be engaged in inner speech on approximately one third of all trials. With generalized linear mixed-effects models fitted to a Gamma distribution, we found significant effects of task relevance but no interaction with inner speech. However, using a hierarchical Bayesian analysis method, we found that trials preceded by task-relevant inner speech additionally displayed lower standard deviation and lower mode compared to all other trials. Due to deviations from the preregistered sampling and analysis procedures, we replicated our findings in Experiment 2. Our results add support to the hypothesis that inner speech serves a functional role in top-down attentional control.