Abstract
Spatial attention is believed to play an essential role in feature binding, with voluntary (top-down) attention demonstrating clear influences on both correct feature-binding and feature-binding errors (Golomb et al, 2014). But attention is not always voluntary—in visual processing, spatial attention can also be captured automatically by stimulus-driven (bottom-up) cues. What happens to feature perception when spatial attention is voluntarily directed to a target location, but inadvertently captured by a distractor elsewhere? Subjects were presented with four colored squares for 50ms. One item (the target) was highlighted with a white border, and subjects reported the target's color by clicking on a colorwheel. To manipulate attentional capture, a salient distractor (four white dots) could surround the target (valid trials), an adjacent item (invalid), or not appear at all (neutral). Probabilistic mixture modeling revealed that subjects' responses were less precise (higher guessing rate, larger SD) in invalid trials, with a significant increase in "swap" errors (probability of misreporting the distractor color instead of the target color). Critically, we supplemented the standard continuous-report task with a confidence report, in which subjects subsequently selected a flexible range of error around their "best-guess" on the colorwheel. In valid trials, the size of the confidence range accurately reflected performance; subjects were significantly less confident when making errors than correct responses. However, in invalid trials, subjects were equally confident when misreporting the salient distractor as when reporting the correct target color, indicating that when attention was captured by the distractor, subjects were nevertheless confident they were correctly reporting the target. Finally, even in invalid trials when the distractor was successfully ignored, we found evidence of feature-distortion errors (repulsion away from the distractor color). These results highlight the significant role of spatial attention on feature binding and reflect a unique feature-binding error pattern induced by stimulus-driven attentional capture.
Meeting abstract presented at VSS 2018