Pre-saccadic attention spreads to stimuli forming a perceptual group with the saccade target.

The pre-saccadic attention shift-a rapid increase in visual sensitivity at the target-is an inevitable precursor of saccadic eye movements. Saccade targets are often parts of the objects that are of interest to the active observer. Although the link between saccades and covert attention shifts is well established, it remains unclear if pre-saccadic attention selects the location of the eye movement target or rather the entire object that occupies this location. Indeed, several neurophysiological studies suggest that attentional modulations of neural activity in visual cortex spreads across parts of objects (e.g., elements grouped by Gestalt principles) that contain the target location of a saccade. To understand the nature of pre-saccadic attentional selection, we examined how visual sensitivity, measured in a challenging orientation discrimination task, changes during saccade preparation at locations that are perceptually grouped with the saccade target. In Experiment 1, using grouping by color in a delayed-saccade task, we found no consistent spread of attention to locations that formed a perceptual group with the saccade target. However, performance depended on the side of the stimulus arrangement relative to the saccade target location, an effect we discuss with respect to attentional momentum. In Experiment 2, employing stronger perceptual grouping cues (color and motion) and an immediate-saccade task, we obtained a reliable grouping effect: Attention spread to locations that were perceptually grouped with the saccade target while saccade preparation was underway. We also replicated the side effect observed in Experiment 1. These results provide evidence that the pre-saccadic attention spreads beyond the target location along the saccade direction, and selects scene elements that-based on Gestalt criteria-are likely to belong to the same object as the saccade target.

Expectations and perceptual priming in a visual search task: Evidence from eye movements and behavior.

An extensive amount of research indicates that repeating target and distractor features facilitates pop-out search while switching these features slows the search. Following the seminal study by Maljkovic and Nakayama (1994), this "priming of pop-out" effect (PoP) has been widely described as an automatic bottom-up process that is independent of the observers' expectations. At the same time, numerous studies highlight the crucial role of expectations in visual attention deployment. Our experiment shows that in contrast to previous claims, PoP in a classic color singleton search task is a mix of automatic processing and expectations. Participants searched for a uniquely colored diamond among 2 same-colored distractors. Target color sequences were either predictable (e.g., 2 red-target-green-distractors trials, followed by 2 green-target-red-distractors trials, and so on) or random. Responses were faster in predictable color sequences than randomly changing ones with equal number of repetitions of target colors on preceding trials. Analyses of observers' eye movements showed that predictability of target color affected both latency and accuracy of the first saccade during a search trial. Our results support the idea that PoP is governed not only by automatic effects from previous target or distractor features but also by top-down expectations. (PsycINFO Database Record (c) 2019 APA, all rights reserved).