Abstract
QUESTION Does attending to a single feature within a surface facilitate perceptual judgments about other features of that surface? METHODS Stimuli were composed of two superimposed fields of dots, each associated with a color and a direction of motion. For each surface, each feature changed slowly and independently along a smooth trajectory. Surfaces thus were defined by time-varying conjunctions of motion and color in feature space. While fixating, observers tracked a single feature (color or motion) of one of the two surfaces and reported discontinuities along its trajectory with button presses. Each trial lasted 10 s and contained 0-3 such discontinuities per field. On approximately 70 percent of the trials, a single discontinuity was also introduced in the untracked feature of either surface with equal probability. At the end of a trial the number of misses and false alarms were provided, and a 3AFC paradigm was used to assess whether observers detected a discontinuity in an untracked feature, and if so in which surface. RESULTS Observers were better at detecting discontinuities in the untracked feature when it occurred in the tracked surface compared to the untracked surface. For example, while tracking the motion of one surface, subjects were better at detecting color discontinuities in that surface compared to color discontinuities in the other surface. CONCLUSION Our results suggest that attending to a feature of a surface recruits attentional mechanisms associated with other features of that surface. Our preliminary results using fMRI suggest that this feature-tracking task may lead to enhanced modulation of hemodynamic responses associated with multiple features of an attended surface.