Recent studies have revealed that memory performance is better when participants have the opportunity to make a choice regarding the experimental task (choice condition) than when they do not have such a choice (fixed condition). These studies, however, used intentional memory tasks, leaving open the question whether the choice effect also applies to incidental memory. In the current study, we first repeated the choice effect on the 24-h delayed intentional memory performance (experiment 1). Next, using an incidental paradigm in which participants were asked to judge the category of the items instead of intentionally memorizing them, we observed the choice effect on judgment during encoding and memory performance in a 24-h delayed surprise test (experiment 2). Participants judged more accurately and quickly and had better recognition memory for items in the choice condition than for items in the fixed condition. These results are discussed in terms of the role of choice in both intentional and incidental memory
