Abstract
Goal: Attention trades off processing resources between attended and unattended locations. This trade-off has been shown for early visual dimensions, i.e., contrast sensitivity increases at the attended locations while decreasing at unattended locations (Pestilli & Carrasco, 2005). How general is this trade-off mechanism? Does it generalize to other basic visual dimensions? Specifically, is increased acuity at attended locations (e.g., Carrasco, Williams, Yeshurun, 2002) accompanied by a decrease in acuity at unattended locations? Here we measured the effects of attention on acuity at cued and uncued locations relative to a neutral (baseline) condition.
Methods: Transient (exogenous) attention was manipulated via non-informative peripheral cues preceding stimulus presentation. On each trial, a precue appeared either at fixation or adjacent to one of two upcoming Landolt squares. After a 60-ms SOA, the two squares (side length=1°; eccentricity=9.4°) appeared for 30-ms to the right and left of fixation. Next, a response cue indicated to the observer the target stimulus (left or right). Observers localized a gap (top or bottom) in the target Landolt square. To assess acuity, we measured 75% gap-size thresholds using an adaptive staircase procedure (Quest). When precue- and response cue-locations matched (valid trial), acuity was measured at cued locations (attended); when they mismatched (invalid trial), acuity was measured at uncued locations (unattended). On neutral trials, two precues appeared 0.5° off fixation indicating stimulus onset without drawing attention to the stimulus.
Results: Acuity increased at valid-cued locations, and decreased at uncued locations, as compared to the neutral condition. This result indicates a trade-off for acuity with transient attention, even when only two stimuli are present. This finding, analogous to that of transient attention on contrast sensitivity, suggests that visual processing trade-offs are a general mechanism of attentional allocation.
Acknowledgments: NIH R01 EY016200-01A2.