Concurrent Working Memory Load May Increase or Reduce Cognitive Interference Depending on the Attentional Set

Perceptual grouping leads to interference when target and distractors are integrated within the same percept. Cognitive control allows breaking this automatic tendency by focusing selectively on target information. Thus, interference can be modulated either by goal-directed mechanisms or by physical features of stimuli that help to segregate the target from distracters. In three experiments, participants had to respond to the left-right direction of a central arrow, flanked by two arrows on each side. Sometimes, instructions requested to also stay vigilant for detecting an infrequent vertical/horizontal displacement of the target. thus loading working memory. Although it has been usually shown that concurrent working memory load hinders target selection, the present research provides evidence that interference may either increase or decrease depending on whether dual tasking draws attention to the grouping (horizontal displacement) or to an orthogonal dimension (vertical displacement), revealing counterintuitive benefits of working memory load.