Micro scanning: Search for a target with very small saccades.

Abstract

This study investigated whether saccadic search exists on a micro scale. Using a high-speed, confocal retinal eye tracker (FET), participants searched for tiny targets within dense displays subtending less than 4 deg2. The participants exhibited goal-directed, exploratory scanning behavior with tiny saccades (median amplitude < 0.5°); saccade amplitude scaled with inter-element distance, fixation duration increased in denser displays, and consecutive saccades followed typical directional dependencies (saccadic momentum and facilitation of return). Search performance and scanpaths resembled those found in large-scale visual search tasks, suggesting functional equivalence across spatial scales. These findings support the view that microsaccades serve the same perceptual and attentional roles as larger saccades. We argue that the distinction between microsaccades and saccades is unnecessary when describing natural, task-driven visual scanning behavior.