Item-specific control of word reading as evidenced by a novel proportion wordness effect

Jacoby and colleagues demonstrated that control processes can adapt at the level of individual stimuli, giving rise to the item-specific proportion congruence (ISPC) effect, whereby items that frequently appear as incongruent produce a smaller Stroop effect. Prior research has focused exclusively on informational conflict (competition between word meaning and ink color), leaving open whether item-specific control mechanisms also affect task conflict (competition between the task sets of word reading and color naming). Across two experiments, we addressed this question. In Experiment 1, using an ISPC manipulation, we replicated the classic reduction of informational conflict for mostly incongruent items but found no evidence of item-specific control of task conflict. In Experiment 2, we introduced a novel item-specific proportion wordness (ISPW) manipulation to vary the likelihood of task conflict at the item level, by presenting items mostly with neutral words or neutral nonwords. Results revealed robust item-specific effects on task conflict and informational conflict, with reductions in both types of conflict for items that were mostly neutral words. These findings clarify the scope of item-specific control: while manipulations of reactive informational control selectively influence informational conflict, manipulations of reactive task control can regulate not only task conflict but additionally informational conflict. Our results refine and extend Jacoby et al.'s original insight, providing initial evidence for item-specific control of word reading, and demonstrating the operation of item-specific control at multiple levels of conflict via an ISPW manipulation that modulated the likelihood of word reading.