Abstract
Alvarez and Cavanagh (2005) have reported that there are independent attentional resources for multiple object tracking (MOT) in two hemifields. Twice as many targets could be successfully tracked when they were distributed between hemifields as when they were all presented within a single hemifield. We investigated whether the attentional tracking system for one hemifield could track the targets that were presented initially in that hemifield, but later moved to the other hemifield. In our experiments, the participants tracked four objects among eight objects. The four targets were divided equally between the left and right hemifields. In one condition, targets moved only within each hemifield in which they were initially presented (Bilateral-to-Bilateral condition). In the other condition, two targets in one hemifield moved toward the other hemifield, while the other two targets remained moving in the initial hemifield, resulting in four moving targets within a hemifield (Bilateral-to-Unilateral condition). Our main interest was comparison between these two conditions, measuring the accuracy of MOT. The results showed that performance in the Bilateral-to-Bilateral condition was better than that in the Bilateral-to-Unilateral condition. In other words, when the initial targets presented in one hemifield moved across to the other hemifield, the attentional resource in each hemifield did not move cross the other hemifield along with the moving targets. This finding suggests that attentional tracking system could be object-based only within each hemifield.
This research was supported by a grant (M103KV010017-06K2201-01710) from Brain Research Center of the 21st Century Frontier Research Program funded by the Ministry of Science and Technology, the Republic of Korea.