Fig. 1.

Experimental setup. A: subjects sat facing an acoustically transparent black screen behind which a mobile robotic arm served to position a speaker/LED assembly for stimuli presentation. The target positioning apparatus is fully occluded by the screen and not visible to the subject. Five laser LEDs (red spots; center, left, and right 20° and up and down 20°) served as fixation references. B: head-fixed subjects localized targets using a laser-mounted joystick guiding a projected pointer spot onto the screen at the perceived location of the target. A button press registered each response. C: target array of 43 locations within ±25° Az by ±20° El (red symbols), including 5 locations coinciding with ocular fixation references (green symbols). resp. button, Response button.