VISUAL SEARCH IN VIRTUAL DEPTH: UNIQUE EYE-MOVEMENT PATTERNS IN SEARCHING 21â„2-D SURFACES.
We investigated eye movement patterns of eleven participants while performing visual conjunction search to compare 2D (fronto-parallel) with virtual depth surfaces (21â„2D - floor perspective). Binocular eye-movements were recorded (EyeLink-II) during choice reaction tasks. 21â„2D wall perspective stimuli were presented as control for perceiving upper 21â„2D elements as â€œfarâ€ versus flat upper 2D elements. Stimuli (24 or 42 distractors) were composed of identical shape and color element attributes. Repeated measure analysis revealed unique search patterns of 21â„2D versus 2D surfaces. We found that in â€œun-interfered searchâ€ (target absence) typically first initiated searching saccades of the 21â„2D surface tended to land at the perceived far region, while in 2D surfaces search began without up or down preference and ended with preference to the upper region. A similar profile of search pattern was found with target present in the 42 distractors condition, but not with 24 distractors. Reaction time was separated for â€œview periodâ€ (from key press to release) and â€œresponse periodâ€ (key release to choice reaction). â€œView periodâ€ RTâ€™s revealed set-size and target presence effects but not surface type effect. This suggests that even though search patterns were influenced by surface type, cognitive decision processes remained unaffected. Our results suggest that 21â„2D conjunctive search patterns reflect common underlying mechanisms of vision for action in natural 3D environments.