Visual-manual response selection produces dual-task interference in auditory-verbal memory encoding

In the present study, we investigated how response selection in a visual-manual reaction-time (RT) task affects encoding in an auditory-verbal free recall memory task. In dual-task conditions, the visual stimulus was presented first, followed by the auditory memory item after either a short stimulus-onset asynchrony (SOA) of 300 ms or a long SOA of 700 ms. After the set of memory items was encoded, participants verbally recalled the to-be-remembered items after performing a short distractor activity. The memory task and RT task were also performed in single-task conditions to assess global dual-task costs. Results showed decreased recall accuracy in the memory task in a dual-task condition compared to a single-task condition, reflecting dual-task costs. Moreover, we observed worse memory performance with short SOA compared to long SOA. In addition, in dual-task conditions we analyzed on a trial-level whether a processing conflict in the RT task (i.e., congruency effect) modulated recall accuracy in the memory task. Results showed that recall accuracy was worse for items encoded during incongruent trials of the RT task compared to congruent trials. Together, the findings indicate that memory for auditory items suffers under dual-task demands with visual-manual response selection. In the RT task, we also observed dual-task costs, with longer RT with short SOA compared to long SOA. Overall, the observed dual-task interference can be interpreted in terms of a shared limited capacity between memory encoding and response selection, but also the roles of attentional prioritization, preparatory effects and overlapping verbal codes are discussed. The present study shows that when people make quick decisions in visual-manual tasks while trying to memorize spoken information into long-term memory, their memory performance declines. It is suggested that decision-making and encoding information into memory interfere with each other and possible explanations like shared limited cognitive resources, attentional prioritization or preparatory effects are discussed. Overall, our findings help to explain why performing two tasks at once can lead to information loss in memory, especially in conflict-driven situations while decision-making.