Questioning conflict adaptation: proportion congruent and Gratton effects reconsidered

Conflict adaptation is one of the most popular ideas in cognitive psychology. It purports to explain a wide range of data, including both brain and behavioral data from the proportion congruent and Gratton paradigms. However, in recent years, many concerns about the viability of this account have been raised. It has been argued that contingency learning, not conflict adaptation, produces the proportion congruent effect. Similarly, the Gratton paradigm has been shown to contain several confounds—most notably, feature repetition biases. Newer work on temporal learning further calls into question the interpretability of the behavioral results of conflict adaptation studies. Brain data linking supposed conflict adaptation to the anterior cingulated cortex has also come into question, since this area seems to be responsive solely to time-on-task, rather than conflict. This review points to the possibility that conflict adaptation may simply be an illusion. However, the extant data remain ambiguous, and there are a lot of open questions that still need to be addressed in future research.