Dissociating congruence effects in letters versus shapes: Kanji and kana.

In order to consolidate the dissociation in feature integration found in earlier studies between letters of the Roman alphabet and corresponding pseudo-letters, the present study used kanji and kana and corresponding pseudo-letters, presented visually, either in isolation or surrounded by congruent or incongruent shape, as targets in a choice-response task with three different response criteria. When the criterion was shape, congruence effects were obtained for both real and pseudo-letters. With the second and third response criteria this result was found for pseudo-letters, but not for letters. These criteria either involved distinguishing between letters and visually similar pseudo-letters or distinguishing between visually similar letters. The dissociation of congruence effects between letters and pseudo-letters was therefore shown to depend on visual similarity between targets, independent of their category. This effect was found to be robust for kanji but not for kana, which is related to distinctions between these two writing systems.