Abstract:

PURPOSE: Whereas attention readily facilitates the detection and discrimination of objects, it is unknown whether it aids in forming the vast voluminous visual space that contains the objects.  Conventional wisdom suggests not, given the e?ortless ease in which we perceive 3D-scenes.  Here, we asked if a di?erential allocation of an ambient attention resource to either the lower visual field (ground) or upper visual field (ceiling) a?ects space perception.
METHODS: In Experiment 1, the observer judged the location of a brie?y presented target (1 sec) placed either on the textured ground or ceiling surface (2x4 LED array spanning 1.4x3m area, 0.15 sec).  Prior to target presentation and to ensure proper ?xation, a dimly lit LED was randomly turned o? for 0.1 sec, 1-3 times within a 3-6 sec ?xation period.  The observer had to correctly report each time the LED ?ickered.  Meantime, he/she attended to either the upper or lower ?eld. 
RESULTS: We found judged location was more accurate for a target on the ground, provided the ground was visible plus the observer directed ambient attention to the lower visual field and not the upper ?eld.  This reveals attention facilitates space perception with reference to the ground.  Our second experiment found judged location of a midair target with both ground and ceiling surfaces present was more accurate when the observer attended to the lower visual field, indicating that the ambient attention e?ect extends to visual space above the ground. 
CONCLUSIONS: These ?ndings underscore attention's role in anchoring visual orientation in space, arguably, a primal event that enhances one's ability to interact with objects within the space.  That the ambient attention's e?ect was contingent on the ground being visible suggests that our terrestrial visual system is best served by its ecological niche.

Key words: attention, space perception, blind-walking task, ground superiority