When a test of attention, such as the d2 test, is repeated, performance improves. These practice benefits threaten the validity of a test because it is impossible to separate the contributions of ability and practice, respectively, to a particular result. A possible solution to this dilemma would be to determine the sources of practice effects, and to use this knowledge for constructing tests that are less prone to practice. The present study investigates the contribution of three components of

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... a d2-like test of attention to practice benefits: targets, distractors, and stimulus configurations. In Experiment 1, we compared practice effects in a target-change condition, where targets changed between sessions, to a target-repetition condition. Similarly, in Experiment 2, we compared practice effects in a distractor-change condition to a distractor-repetition condition. Finally, in Experiment 3, we compared practice effects in a position-repetition condition, where stimulus configurations were repeated within and between tests, to a position-change condition. Results showed that repeating targets and repeating distractors contribute to practice effects, whereas repeating stimulus configurations does not. Hence, in order to reduce practice effects, one might construct tests in which target learning is prevented, for example, by using multiple targets.