Interaction between global optic flow and local optic flow in visual search

Abstract

Optic flow is important perceptual information for regulating behavior in humans and other organisms (observers) with visual organs. This study investigated the effects of global optic flow (GOF) caused by observer movement and local optic flow (LOF) resulting from object movement on visual search. In this experiment, GOF consisted of a group of dots diffusing from the center of the screen to the outside of the screen with constant acceleration; the LOF was a single ring of dots expanding with constant acceleration. LOF was randomly generated from one of the eight placeholders equidistant from the center of the screen and equally spaced from each other. The objective was to visually locate and distinguish the numbers (targets) that appeared after LOF vanished, both with and without GOF. The interaction between “the positional relationship between LOF and the target” and “the time interval between the disappearance of LOF and the presentation of the target” was significant in the reaction time. Therefore, the expanding ring may have served as a cue to focus on the diagonal target within the screen. Additionally, an analysis of the distribution of gaze data showed that when GOF was presented, the gaze was drawn more frequently through its central region. According to these results, the gaze was directed toward the area where the GOF and LOF were parallel.