Abstract
Goal. Feature-based attention (FBA) modulates the perceptual space with both a monotonic profile (i.e., feature-similarity gain) and a non-monotonic profile (i.e., surround suppression). An important question is whether the profile of attentional modulation is a fixed property of attention system or is adaptable to task demands. We hypothesized that the attentional profile depends on perceptual contexts to ensure efficient processing. Here, we explored this hypothesis by manipulating levels of feature competition between a target and distractors. Methods. In the primary task, participants viewed a rapid serial visual representation (RSVP) of multiple stimuli at the center of the screen, which consisted of orientation-filtered Gaussian noise. The target was filtered around a narrow band in a random orientation (bandwidth: ±5°), while the masks contained a range of orientations that were either close to the target (±5° to ±45°) – the high competition condition, or away from the target (±50° to ±90°) – the low competition condition. We manipulated FBA through an orientation precue before the central RSVP and instructed participants to detect the cued target. Meanwhile, we employed a secondary task in which participants monitored two peripheral gratings on both sides of the center RSVP stream for a brief contrast decrement in one of the gratings. We systematically sampled the gratings’ orientations away from the cued orientation and used performances in the secondary task to measure the attentional profile. Results. Performances in the primary task were well equated between high and low competition conditions. For the secondary task, we only found a non-monotonic surround suppression profile in the high competition condition, but not in the low competition condition, which suggests a flexible deployment of different attentional profiles. Therefore, the surround suppression mechanism may be deployed to effectively isolate the target orientation when the task requires resolving a high degree of perceptual competition.