First impressions are lasting impressions: A primacy effect in memory for repetitions

Two experiments demonstrated that the encoding of a repeated object is biased toward the attributes of its first presentation. In Experiment 1, subjects saw objects five times each, but either the first presentation or the fifth presentation was the mirror reverse of the standard orientation seen on the other four trials. When recognition was tested with both orientations simultaneously, subjects reported seeing only the single mirror-reverse orientation more often if it was the first presentation than when it was the fifth presentation, and seeing only the standard orientation more often if it was presentations 1–4 than when it was presentations 2–5. A second experiment demonstrated that this primacy effect generalized to size changes. This pattern of results is consistent with the hypothesis that top-down biases affect what subjects learn: The first representation established for a stimulus is likely to influence the encoding of subsequent repetitions.