Sequence Knowledge on When and What Supports Dual-Tasking

Abstract

The constraints in overlapping response selection have been established in dual-tasking studies with random sequence of stimuli and responses as well as random stimulus onset asynchrony (SOA). While this approach makes it possible to control for advance activation of upcoming stimuli or responses, it leaves open whether such preparatory processing can indeed influence dual-task performance. We investigated whether and how the sequence of stimuli and responses and the sequence of SOAs can be learned and used under dual-tasking. In each trial, participants (N = 28 in Experiment 1 and N = 30 in Experiment 2) were first presented with a random two-choice task followed by a four-choice Serial Reaction Time Task (SRTT), presented in a sequence of length four (position sequence). The SOA (timing) sequence also had length four. In test phases, one or both of the sequences were randomized. Results showed that both position and timing sequences were learned and supported dual-task performance, suggesting that predictive processing with respect to timing and identity of stimuli and responses can help to circumvent the response selection bottleneck constraints. Furthermore, in contrast to previous work on acquisition of interval sequences in single tasking, we found that the sequence of what (i.e. stimulus) and the sequence of when (i.e. interval between two tasks) contributed independently to performance.

Keywords: SRTT; action effect of response; sequence learning; stimulus-response sequence; temporal sequence.

Figure 1

The dual-tasking setup. On each trial, participants completed a two-choice task (Task 1; stimuli and responses: 1 or 2) and a four-choice task (Task 2, SRTT; stimuli X at the upper, lower, left or right position; response with corresponding arrow key). The order of stimuli in the two-choice task was random. The delay between stimulus onset in the two-choice task as well as the sequence of positions in the four-choice task followed fixed sequences of length four.

Figure 2

Mean reaction times (RTs) for the two-choice task and the four-choice task (SRTT) in three types of blocks in Experiment 1 plotted with 95% within subjects confidence intervals based on the error variance of block (Masson & Loftus, 2003). The RTs are calculated from the onset of the particular stimulus of interest. The exact values can be found in Appendix Table A2.

Figure 3

Mean RTs with timing sequence, stimulus sequence and SOA factors for the two-choice task and the four-choice task (SRTT) in Experiment 2 plotted with 95% within subjects confidence intervals based on the error variance of timing sequence × stimulus sequence (Masson & Loftus, 2003). The exact values can be found in Appendix Table A4.