Conceptual response distance and intervening keys distinguish action goals in the Stroop color-identification task

In previous studies, a physical response-distance effect was found in the two-choice Stroop color-identification task, with the Stroop effect being larger when the two response keys were physically close together than when they were far apart. In the present study, we found a conceptual response-distance effect, with the Stroop effect being larger when the response keys were conceptually close (labeled as "5" and "6") than when they were conceptually far (labeled as "1" and "9"). Moreover, a response-distance effect due to pure physical distance was not evident; rather, the effect was found only when additional keys were placed between the two far response keys. These results are in agreement with a view that response keys are coded as action goals, with farther conceptual distance and additional keys helping distinguish the action goals. The results are difficult to reconcile with accounts that place emphasis on the physical separation of the effectors or their inanimate extensions.