The item-specific proportion congruency effect can be contaminated by short-term repetition priming.

The item-specific proportion congruency (ISPC) effect reflects the phenomenon that Stroop congruency effects are larger for Stroop items that are more likely to be congruent (MC) than incongruent (MI). While the ISPC effect is purported to reflect long-term memory associations, the proportion manipulation entails that stimulus repetitions vary as a function of the MC and MI conditions, suggesting that a short-term repetition priming process may also contribute. In the present study, we investigated whether the ISPC effect reflected contributions from separate long-term associative learning and short-term repetition priming processes. To do so, the magnitude of the ISPC effect was compared when stimulus repetitions were present and absent. While the ISPC effect was robust, it was revealed that removing stimulus repetitions significantly attenuated the effect. Overall, the present study indicates the ISPC effect can reflect contributions from both short-term repetition and long-term memory processes.