Sequential modulation of across-task congruency in the serial reaction time task.

While detrimental effects of dual-tasking on the acquisition and usage of sequence knowledge in the Serial Reaction Time Task (SRTT) have been attributed to the integration of regularly and randomly sequenced events, direct evidence for across-task integration has been scarce. In two experiments, we paired two spatial tasks: A visual-manual SRTT (serial reaction time task) of length 4 and a two-choice task with random order of stimuli. We reasoned that across-task integration might result in SRTT- and two-choice task events being stored and retrieved together. Therefore, RT might be influenced by current congruency as well as by whether it is repeated or altered from the congruency level encountered for this SRTT event in the last loop of the sequence. We observed such a modulation in two experiments, suggesting that across-task integration indeed takes place and that the detrimental effect of dual-tasking on sequence learning is, at least in parts, based on across-task integration.