Experiments in Visual Localization.

For an observer viewing in a normally-illuminated and structured visual field EEPI-driven cancellation mechanisms are not normally involved in the determination of visual localization of objects in the visual field either relative to each other or relative to visual norms such as the perceived eye-level horizontal or perceived median plane. In darkness EEPI-driven cancellation mechanisms play a central role in determining visual localization of objects relative to visual norms. EEPI-driven cancellation mechanisms play a central role in intersensory localization e.g. matching locations of sound and light in either darkness or light if visual capture of the sensory information regarding location via the other modality is prevented. In normally-illuminated visual fields EEPI is not suppressed. Nor is the output of the cancellation mechanism. However, what is suppressed in the normally-illuminated field is the involvement of EEPI in visual localization. Thus under some conditions the EEPI-driven cancellation mechanism may remain involved in other aspects of perception such as a comparison of localization of auditory and visual targets although it has no influence on visual localization.