Far from being “memoryless”, the phenomenal appearance of an ambiguous display depends in complex ways on the recent history of similar perceptions. Given several possible appearances, the continued dominance of one appearance mitigates against its renewed dominance at a later time. This “negative priming” effect is likely caused by neural adaptation. At the same time, continued dominance of one appearance mitigates in favor of its renewed dominance when stimulation resumes after an interruption. This “positive priming” effect may reflect some kind of neural facilitation. We have used a multi-stable, kinetic depth display to disentangle these positive and negative priming effects. We report that negative priming builds up and decays in seconds, whereas positive priming builds up in seconds and decays in minutes. Moreover, unambiguous displays induce negative, but not positive, priming. This difference, together with their disparate time-courses of recovery, render the two effects cleanly dissociable.