Change Localization

Participants first saw a 5-item encoding array for 500 ms at a viewing distance of 70 cm. The items were equally spaced around an imaginary circle that was centered on the screen, and spanned 1/3 of the screen's vertical height. The encoding array was followed by a 1000-ms delay and then the test array. Participants used the mouse to click on the one changed item. Accuracy was stressed, and responses were untimed. In one version of the task, the five items were colored rectangles, one of which changed color in the test array. In a second version, the items were colored shapes (e.g., circle, star, etc), and the changed item differed in both shape and color from the corresponding item in the encoding array. Each version had 60 trials with order counterbalanced across participants. The WM capacity score was calculated by multiplying the percentage of correct responses by the memory array size (34).

Multiple Change Detection

This task used the same stimuli as the presentation arrangement, and delay interval as the Change Localization Task. However, the test array contained 0, 1, 2, or 5 changed items (p = .25 for each) relative to the encoding array. Participants indicated change or no change using left and right index fingers on a keyboard. A total of 240 items were presented in each version, 60 of each trial type.