The authors conducted 4 repetitio priming experiments that manipulated prime duration and prime diagnocity in a visual forced-choice percceptual identification task. The strength and direction of prime diagnosticty produced marked effects on identification accuracy, but those effects were resistant to subsequent changes of diagnosicity. Participants learned to associate different diagnocities with primes of different durations but not with primes presented in different colors. Regardless of prime diagnosticity, preference for a primed alternative covaried negatively with prime duration, suggesting that even for diagnostic primes, evidence discounting remains an important factor. A computational model, with the assumption that adaptation to the statistics of the experiment modulates the level of evidence discounting, accounted for these results.