Concurrent deployment of visual attention and response selection bottleneck in a dual-task: Electrophysiological and behavioural evidence

ABSTRACT

Visual attention and response selection are limited in capacity. Here, we investigated whether visual attention requires the same bottleneck mechanism as response selection in a dual-task of the psychological refractory period (PRP) paradigm. The dual-task consisted of an auditory two-choice discrimination Task 1 and a conjunction search Task 2, which were presented at variable temporal intervals (stimulus onset asynchrony, SOA). In conjunction search, visual attention is required to select items and to bind their features resulting in a serial search process around the items in the search display (i.e., set size). We measured the reaction time of the visual search task (RT2) and the N2pc, an event-related potential (ERP), which reflects lateralized visual attention processes. If the response selection processes in Task 1 influence the visual attention processes in Task 2, N2pc latency and amplitude would be delayed and attenuated at short SOA compared to long SOA. The results, however, showed that latency and amplitude were independent of SOA, indicating that visual attention was concurrently deployed to response selection. Moreover, the RT2 analysis revealed an underadditive interaction of SOA and set size. We concluded that visual attention does not require the same bottleneck mechanism as response selection in dual-tasks.

KEYWORDS:

• Electrophysiology
• N2pc
• Psychological refractory period
• Response selection bottleneck
• Visual attention
• Visual search

Acknowledgements

We thank Werner Sommer for giving us the opportunity to conduct the EEG experiment in his lab.

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes

1. As one reviewer pointed out, in the conjunction search task, there was an imbalance regarding the display distribution of the target colour green, which could have facilitated target selection. In more detail, there were 3 versus 2 green items (and 1 vs. 2 red items) for set size 8 as well as 5 versus 4 green items (and 3 vs. 4 red items) for set size 16 presented to the left and right of fixation (see Figure 2). However, this imbalance, which was caused by the methodological need to have an equal number of items on the left and right side of the display (including one target and the distractors), did not facilitate target selection in the present study. There was a large set size effect on visual search time and on the N2pc amplitude. Both set size effects indicate that the participants performed the visual search task by deploying visual attention serially around the items of the display and that they bound both stimulus features—that is, the colour and the form feature—during that process. Thus, there is evidence that the target-colour imbalance in the present search task did not obscure the serial character of target selection.

Additional information

Funding

This work was supported by a Deutsche Forschungsgemeinschaft grant [grant number Schu 1397/5-2], awarded to Torsten Schubert. Christina B. Reimer is supported by the Elsa-Neumann Scholarship.