Abstract
One popular task for measuring attentional capacity is multiple object tracking (MOT), where observers attentively track multiple moving target items among a set of identical distractors. MOT performance depends on a variety of factors, including the number of targets and their speed (Alvarez and Franconeri, 2007). Thus, the MOT task provides two measures of attentional capacity: (1) the number of items that can be tracked at a fixed speed, (2) the maximum speed at which a fixed number of items can be tracked. Here, we explored whether these measures of attentional capacity can be increased through an adaptive training regime. A threshold procedure was used to determine the speed at which two subjects could track four targets among eight distractors (mean speed = 5.3 deg/s). Subjects then completed twenty sessions of MOT practice (40 trials per day), with the object speed on each trial adaptively updated. When all targets were accurately tracked on two consecutive trials, speed was increased by 1 deg/s. When any targets were missed, the speed was decreased by 1 deg/s. After the last session of training, we assessed the number of items that could be tracked at the initial pre-training speed. Over twenty sessions of training, subjects increased the speed that they could reliably track four objects from 5.3 deg/s to an average speed of 12.3 deg/s. The maximum speed they could track objects was proportional to the time spent training (r = .843, p <.001). After training, both subjects could track six objects at their initial baseline speed. These findings indicate that it is possible to dramatically increase the capacity of visual attention through training. Furthermore, training along one measure of capacity (increasing speed) transferred improvements to the second measure of capacity (increasing number of targets), suggesting that a single resource constraint underlies both limits.