When diverting attention improves performance: Attention trades off spatial resolution

摘要

GOAL. Spatial resolution is maximal at the fovea and declines with eccentricity. Although heightened resolution is useful in most circumstances, it is not always optimal. For instance, in texture segmentation tasks constrained by spatial resolution, increased resolution can be detrimental. In these tasks, performance peaks at mid-periphery, where resolution is optimal for the texture scale, and drops at peripheral locations, where resolution is too low, and central locations, where resolution is too high. Exogenous (involuntary) attention automatically increases spatial resolution, improving performance at peripheral locations but impairing performance at central locations, where resolution is already too high (Yeshurun & Carrasco, Nature 1998). Here, we investigated whether and how exogenous attention affects performance at unattended areas in texture segmentation tasks. METHODS. Observers had to detect (Exp.1) or discriminate the shape of (Exp.2) a texture patch embedded in a texture display. The patch could appear at several eccentricities along the horizontal meridian. Exogenous attention was manipulated using uninformative peripheral precues. With valid cues, the locations of the precue and response cue matched, with invalid cues, they did not. Cueing effects were evaluated against a neutral (distributed) attention condition. Response cues were used to eliminate location uncertainty. Eye fixation was monitored. RESULTS. Consistent with previous studies, in both experiments we found that: (a) performance in the neutral condition peaked at mid-periphery; (b) valid cues improved performance at peripheral locations, where resolution was too low, and impaired performance at central locations, where resolution was too high. Interestingly, with invalid cues, performance decreased at peripheral locations but improved at central locations, where higher resolution hinders performance. CONCLUSION. Our results depict exogenous attention as an inflexible attentional mechanism that trades off spatial resolutiona??increasing resolution at the attended location while decreasing it elsewhere. This decrement in resolution at unattended areas reveals a paradoxical situation in which diverting attention actually improves performance.