To group or not to group: an ecological consideration of the stroop effect.

Eight experiments are reported that examine the contextual factors that influence the magnitude of color-word interference in the Stroop task. In Part 1 of the paper (Experiments 1-4) we varied letter-letter grouping using Gestalt principles of proximity and similarity. In Part 2 of the paper (Experiments 5-8) we varied word-color grouping using the Gestalt principles of similarity and common fate. The magnitude of the Stroop effect was strongly influenced by changes in both letter-letter grouping in the color-word and word-color grouping. Overall, the results suggest two ways in which perceptual organization influences the magnitude of Stroop color-word interference and more generally, that there are systematic principles that govern the impact of visually presented words across a variety of laboratory contexts and the real world.