Incidental learning of incongruent items in a manual version of the Stroop task.

Two experiments refine the incidental learning hypothesis of incongruent items during color-naming. In Exp. 1, the size of the incongruent item set was manipulated in a manual Stroop task. In Version 4, four different incongruent items were presented; in Version 8, eight different incongruent items were presented; and in Version 12, 12 different incongruent items were presented. Analysis showed color-naming response time was roughly equivalent for neutral and incongruent items in Version 4. Conversely, the Stroop effect not only was manifest but also was equivalent in Versions 8 and 12. In Exp. 2, the role of the phonological loop in the Stroop effect was investigated using Version 4 of Exp. 1. The Experimental group repeated aloud the syllable "LA" during the Incongruent color-naming condition. Articulatory suppression resulted in a significant increase in Incongruent color-naming response time. Implications for the interpretation of Stroop data are discussed.