Abstract
Playing a team sport or taking children to the beach involves tracking multiple moving targets. Resource theory asserts that a limited resource is divided among targets, and performance reflects the amount available per target. Holcombe and Chen (2011) validated this with evidence that tracking a fast-moving target depletes the resource. Using slow speeds Alvarez and Cavanagh (2005) found the resource consumed by additional targets is hemisphere-specific. They didn’t test the effect of speed, and here we tested whether speed also depletes a hemisphere-specific resource. To put any speed limit cost in perspective, we modeled a "total depletion" scenario- the speed limit cost if at high speeds one could not track the additional target at all and had to guess one target. Experiment 1 found that the speed limit for tracking two targets in one hemifield was similar to that predicted by total depletion, suggesting that the resource was totally depleted. If the second target was instead placed in the opposite hemifield, little decrement in speed limit occurred. Experiment 2 extended this comparison to tracking two vs. four targets. Compared to the speed limit for tracking two targets in a single hemifield, adding two more targets in the opposite hemifield left the speed limit largely unchanged. However starting with one target in both the left and right hemifields, adding another to each hemifield had a severe cost similar to that of the total depletion model. Both experiments support the theory that an object moving very fast exhausts a hemisphere-specific attentional tracking resource.
Meeting abstract presented at VSS 2012