Abstract
Goal: Objects appearing in the visual periphery can automatically capture attention. The brief flash of a single cue, for example, rapidly enhances contrast sensitivity for subsequent stimuli in its vicinity. Feature singletons (e.g., a red shape among green ones) can also capture attention in a variety of tasks. Here, we evaluate whether a peripheral cue that enhances contrast sensitivity when it appears alone has a similar effect when it appears as a color singleton, with the same stimuli and task. Methods: Observers discriminated the orientation of a Gabor patch that appeared at one of two isoeccentric locations on opposite sides of an imaginary 45º diagonal. A red or green cue disc was flashed 106 ms before the Gabor’s onset, either near the Gabor’s location (valid cue, 50% likely) or near the opposite location (invalid cue). In a random half of trials the cue disc appeared alone, and in the remainder it was presented amongst 15 others of the opposite hue, all arranged in an isoeccentric ring. The discs’ colors were equated in subjective luminance. Observers were explicitly informed that all the discs were task-irrelevant. Results: By varying the contrast of the Gabor we obtained psychometric functions of performance. In the single cue condition, contrast thresholds as well as response times were lower on valid than invalid trials, indicating that attention was drawn towards the location of unique contrast change against the background. In the singleton condition, however, performance was not affected, indicating that attention was not drawn towards the disc with chromatic contrast relative to all other discs in the display. Thus, feature singletons and single cues shift attention in different ways.
Meeting abstract presented at VSS 2012