Center-Surround Antagonism and the Influence of Disparity upon the Perception of Speed in Young and Aging Observers

Cory Lance Burton, Western Kentucky University


Two experiments were designed to evaluate the influence of binocular disparity in a target’s surround upon the perceived speed of a moving target, in both young and aging observers. Contextual information is known to influence the perceived speed of a target. For example, studies have shown that contextual parameters, such as surround velocity (Norman, Norman, Todd, & Lindsey, 1996; Tynan & Sekuler, 1975), landmark presence (Brown, 1931), landmark density (Gogel & McNulty, 1983), and background texture and stimulus contrast (Blakemore & Snowden, 2000; Nguyen-Tri & Faubert, 2007) can alter an observer’s perception of target speed. Other research, using discrete center-surround type stimuli, has shown modulatory effects of surround disparity upon neuronal responses in cortical area MT (Bradley & Andersen, 1998). Experiment 1 was designed to examine the degree to which crossed, uncrossed, and zero disparities in a target’s moving surround alter the perceived speed of the target. Given the fact that aging is widely known to affect performance on motion-related tasks (e.g., Norman, Ross, Hawkes, & Long, 2003). Experiment 2 was designed to test the effects of aging upon perceived velocity under conditions equivalent to those used in Experiment 1. The results of Experiment 1 demonstrated that a target’s perceived speed is dependent upon its position in depth relative to its surround when both regions move in the same direction. Experiment 2 showed that aging alters the perceived speed of moving targets, such that perceived speed is dependent upon a target’s depth relative to its surround, this effect occurring independently of the surround’s direction of motion.