Abstract
Attention can be directed endogenously, based on task-relevant goals, or captured exogenously, by salient stimuli. While recent studies have shown that endogenous attention can facilitate behavior through dissociable sensitivity (sensory) and choice bias (decisional) mechanisms, it is unknown if exogenous attention also operates through dissociable sensitivity and bias mechanisms. We tested human participants on a multialternative change detection task with exogenous attention cues, which preceded or followed change events in close temporal proximity. Analyzing participants’ behavior with a multidimensional signal detection model revealed clear dissociations between exogenous cueing effects on sensitivity and bias. While sensitivity was, overall, lower at the cued location compared to other locations, bias was highest at the cued location. With an appropriately designed post-cue control condition, we discovered that the attentional effect of exogenous pre-cueing was to enhance sensitivity proximal to the cue. In contrast, exogenous attention enhanced bias even for distal stimuli in the cued hemifield. Reaction time effects of exogenous cueing could be parsimoniously explained with a diffusion-decision model, in which drift rate was determined by independent contributions from sensitivity and bias at each location. The results suggest a mechanistic schema of how exogenous attention engages dissociable sensitivity and bias mechanisms to shape behavior.
Highlights
Selection of behaviorally relevant information can occur either by endogenous engagement of attention, based on task-relevant goals, or by exogenous capture of attention, by salient sensory events[1,2,3,4]
We investigated the effects of exogenous cueing of attention on perceptual processing and decision-making
Half-contrast cues produced a significant improvement in d′ at the cued location (Cu: attention effects (AE)(d′) = 0.26+/−0.07, p < 0.001; Supplementary Fig. S2), but only a weak reduction in d′ at uncued locations (Ip: AE(d′) = −0.18+/−0.09, p = 0.008, Co: AE(d′) = −0.2+/−0.1, p = 0.185, Op: AE(d′) = −0.11+/−0.06, p = 0.060). This global attentional effect, and the local visual suppression effect, of exogenous cueing, were supported by two other lines of evidence, which are outlined in the Supplementary Results. These results indicate that, sensitivity at the exogenously cued location was lowest compared to other locations, the attentional effect of exogenous cueing − computed by comparing sensitivity in pre-cue versus post-cue trials (Fig. 1B) − was consistent with a global reallocation of sensory processing resources from uncued locations toward the cued location
Summary
Selection of behaviorally relevant information can occur either by endogenous (top-down) engagement of attention, based on task-relevant goals (e.g. monitoring a traffic light), or by exogenous (bottom-up) capture of attention, by salient sensory events (e.g. a flash of lightning)[1,2,3,4]. It is increasingly clear that attention, when cued endogenously, facilitates behavior through at least one of two mechanisms: i) by enhancing the sensory processing of attended information, often at the cost of unattended information, and ii) by prioritized gating of attended information for guiding perceptual decisions[20,21,22,23,24] These component mechanisms have been recently studied in the context of endogenous attention tasks[25,26,27,28,29,30] using signal detection theory (SDT), a highly successful framework for the analysis of behavior[31,32]. Combining the m-ADC model with a drift-diffusion model[36], we develop a mechanistic framework for understanding how exogenous cueing improves behavioral accuracies and reaction times through systematic effects on sensitivity and bias
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