Task-separation in dual-tasking: How action effects support the separation of the task streams

Abstract

Dual-task costs might reflect a direct consequence of confusions on the task-set level as both tasks are integrated into a single task-set, instead of two separate task-sets. In order to prevent this integration-driven interference, the two task streams have to be separated. Under three experimental conditions we investigated whether in a dual-task setting such separated task processing can be elicited by providing separated action effects for both tasks. Building on the finding that implicit sequence learning is hampered under dual-tasking conditions, we used it as an indicator for successfully separated task processing. To this end, we compared the implicit sequence learning effect under a single-task condition (baseline condition) to that under a dual-task condition either with separated action effects (action-effect condition) or with conjoined error feedback at the end of each trial (feedback condition): Learning should be unaffected under the former and reduced under the latter experimental condition. In all three conditions, the participants performed a visual-manual and an auditory-manual discrimination task which were always presented concurrently. The results show that, compared to the single-task condition, under dual-task conditions implicit sequence learning is hampered when only a conjoined error feedback is given, but is largely unaffected by dual-tasking when separated action effects are presented. Overall this suggests that whenever two tasks in a dual-task situation appear concurrently, they seem to get integrated into a single task-set by default. Yet, manipulations like the presentation of separated action effects could help to elicit a separated task processing, thus strengthening the representation as two separate task-sets.