What is primed in priming from imagery?

Priming from imagery is typically weaker than that from perception. This has been interpreted as resulting from weaker activation of perceptual processes. However, for imagery and perception, commonality is only half the story: Each is also characterized by specific processes. If priming can be due to both unshared and shared components of imagery and perception, then it should be possible to observe greater priming from imagery than from perception. Two new priming experiments were designed to test this hypothesis, while controlling incidental task differences. In both experiments, participants studied objects by counting their parts (from a mental image or a picture). Experiment 1 used a word-picture matching test task, which was hypothesized to depend on stimulus processing specific to perception, and Experiment 2 a size judgment test task, which was hypothesized to depend on retrieval and generation processes specific to imagery. As predicted, priming for perceived objects was greater than priming for imagined objects in the word-picture matching task. Conversely, in the size judgment task, more priming from imagery than from perception was observed. These results support the conclusions that (a) imagery and perception have substantial unshared processes, and (b) these processes contribute to priming.