Exhausting attentional tracking resources with a single fast-moving object

Abstract

Highlights• Attentional limits were assessed with wide spacing to avoid object interference.• The speed limit for tracking two objects was much slower than for tracking one.• Attentional resource theory of tracking was supported.• At least two tracking resources, one in each hemisphere.• At fast speeds, performance tracking two no better than predicted by capacity of one. AbstractDriving on a busy road, eluding a group of predators, or playing a team sport involves keeping track of multiple moving objects. In typical laboratory tasks, the number of visual targets that humans can track is about four. Three types of theories have been advanced to explain this limit. The fixed-limit theory posits a set number of attentional pointers available to follow objects. Spatial interference theory proposes that when targets are near each other, their attentional spotlights 2 mutually interfere. Resource theory asserts that a limited resource is divided among targets, and performance reflects the amount available per target. Utilising widely separated objects to avoid spatial interference, the present experiments validated the predictions of resource theory. The fastest target speed at which two targets could be tracked was much slower than the fastest speed at which one target could be tracked. This speed limit for tracking two targets was approximately that predicted if at high speeds, only a single target could be tracked. This result cannot be accommodated by the fixed-limit or interference theories. Evidently a fast target, if it moves fast enough, can exhaust attentional resources.

Resource demands of object tracking and differential allocation of the resource

“…As we described in the Hemisphere Specificity section above, Holcombe and Chen (2012) found evidence for the hemisphere specificity of the resource in their Experiment 3. In that experiment, however, the durations of the trials did not differ for different speeds, meaning that for trials testing fast target speeds, the targets traveled much farther than they did on slow-speed trials.…”

“…Experiment 1: Testing the hemifield specificity of the tracking resource Holcombe and Chen (2012) in their Experiment 3 found that the maximum target speed that could be tracked (68 % threshold) with two targets in a hemifield was no better than would be expected if participants had ignored one of the targets and simply guessed whenever it was probed (the capacity-one performance benchmark). An alternative theory that makes the same prediction is that the resourceversus-performance function is linear.…”

“…Since spatial interference (crowding) is known to be greater when objects are presented unilaterally rather than split across hemifields (Liu, Jiang, Sun & He, 2009), the observed decrease in tracking performance when the targets were presented unilaterally might have been due to spatial interference. Holcombe and Chen (2012) addressed this issue by using a display in which the objects were kept widely separated to avoid crowding. After finding the maximum speed at which observers could track one target, the researchers tested how this speed limit was affected when observers were asked to track an additional target.…”

“…The capacity-one performance benchmark, first described by Holcombe and Chen (2012; which they termed the capacity-one model), calculates the performance level expected if participants track only one target and completely ignore the second. This puts any cost of splitting attention in perspective by comparing the cost to what would occur if participants could only track one object.…”

Close encounters of the distracting kind: Identifying the cause of visual tracking errors

“…Specifically, some researchers have argued that a flexible resource determines the resolution of spatial attention and that certain display factors, such as speed, independently consume this resource, leading to worse spatial resolution for faster moving than for slower moving objects Holcombe & Chen, First targets flash (1). Next they move for 6 s (2).…”