Roles of target detection and behavioral response on pupil dilation and concurrent memory: An attentional boost study.

The attentional boost effect (ABE) describes the counterintuitive phenomenon in which detecting and responding to behaviorally relevant targets improves the processing of unrelated stimuli presented at the same time. To better understand the mechanisms behind this dual-task enhancement, we compared behavioral and pupillary measures of the ABE, isolating the contributions of perceptual target detection and response requirements. Participants monitored a rapid serial presentation of a specific target letter (e.g., "E"), a large set of nontarget letters, and blank (baseline) trials in equal proportions. In one condition, they pressed a button for the target letter only; in another, for the nontarget letters. Experiment 1 assessed the ABE behaviorally by measuring memory for concurrently presented photographs. Experiment 2 assessed physiological responses via pupillometry during the same letter task (without image encoding). Memory was enhanced for target-paired images when participants responded to targets and showed a modest enhancement for both target- and nontarget-paired images when participants responded to nontargets. This is consistent with the idea that both perceptual and response goals modulate the ABE. Pupil dilation was also sensitive to both factors but was more strongly driven by response. These findings highlight the dual contributions of detection and response in producing the ABE.