Abstract
Previous research using visual search tasks and target localization tasks demonstrates that the visual system can implicitly learn base rate information and then use this information to guide visual attention. Furthermore, it appears that this information is often implicit. Here we investigated whether similar effects can be found with a change detection task. In this task, subjects were shown an array of six colored shapes (each being one of four possible shapes and one of four possible colors). After viewing the array for 2 seconds, one of the shapes changed color. The subject's task was to identify the postchange color in a 4AFC recognition question. One hundred training trials were presented, during which we manipulated the probability of change for each shape (each shape changed color on either 65, 25, 10, or 0 of the 100 trials). Following 100 training trials, subjects completed 20 test trials during which each shape was equally likely to change color. Accuracy during the test trials was higher for shapes that had a high probability of change during the training phase than for shapes that never changed. Therefore, subjects incidentally learned the varying probabilities and used this information to strategically guide visual attention. Furthermore, subjects did not have explicit knowledge of the probability manipulation, suggesting the information used to guide attention was implicit.