Action matters! Target report technique affects interference between visually guided touch and multiple-object tracking

When participants carry out concurrent tasks there can be overlap in action plans. This study shows the effects of action-plan overlap in a multiple-object tracking (MOT) task where participants tracked 1-4 targets while touching any items that changed colour during the item motion phase of tracking trial (either targets or distractors in MOT). We manipulated the way that participants reported MOT targets at the end of the trial. Participants (untimed) either reported targets by touching them with the index finger of their dominant hand (maximal overlap between target report and touching items that changed colour) or typed in letters corresponding to targets with their non-dominant hand (minimal overlap). Target report had no effect on single-task MOT performance. However, when participants had to touch items that changed colour during tracking, MOT was significantly worse when participants reported targets by typing them in rather than touching them and it also took participants longer to touch items that changed colour even though these colour changes preceded target report by 7-8 s. Nonetheless, target-report did not affect the performance discrepancy between the target- and distractor-touch conditions, which suggests performance differences between these two conditions reflect differences in attentional selection rather than action-plan overlap.