Procedure. At the beginning of the experiment, subjects studied the categorized list of 90 words. The list was blocked by category. Subjects saw a category name for 2 s (e.g., VEGETABLES) followed by each word for 2 s (e.g., cucumber) with a 500-ms interstimulus interval between words. The order of categories in a list was randomized. In addition, categories assigned to each of the three sets were evenly distributed throughout the study phase such that categories assigned to any of the three conditions did not occur more frequently near the beginning or end of the study list. The items within each category were also randomly ordered for each subject. Subjects were instructed to study the words as they appeared so that they would be able to recall them later.
After the study phase, all subjects played a video game (Pac-Man) on the computer for 3 min. After this filler task, subjects completed the initial test. Before this test, subjects were warned against guessing and were told that the experi- menter might ask them to recall the items again later in the experiment. Overt and covert retrieval trials were intermixed during the initial test. Subjects were given the category name and instructed to mentally recall the words they had studied that belonged to the category for 40 s. After 40 s had elapsed, an instruction appeared at the top of the screen. In the overt retrieval condition, a text field appeared, and the subjects were told to type as many of the words as they could recall for 20 s, whereas in the covert retrieval condition, the subjects were told to continue thinking of the words they had recalled, but they were not instructed to type them. At the end of each recall trial subjects typed the total number of words they had recalled from that category (e.g., 3). This was done to gain some estimate of the number of words recalled during covert retrieval.
After subjects completed the initial test, they played a video game (Tetris) on the computer for 15 min. Then, all subjects completed a final free recall test. Subjects were asked to recall words for 10 min by typing as many studied items from as many categories as possible, but they were also warned against guessing. At the end of the experiment the subjects were debriefed and thanked for their participation.