Is there a genuine advantage to the upper part of words during lexical access? Evidence from the Stroop task.

A number of recent visual-word recognition and reading experiments have concluded that the upper part of words is more important for lexical access than is the lower part, which conforms with Huey's (1908) observation. Here, we examined whether this phenomenon may simply be due to the fact that words in Indo-European languages tend to have a higher number of confusable letters in the lower than in the upper part. We manipulated the letter ambiguity of the upper and lower parts of words in two experiments in which we asked participants to report the presentation color of the upper and lower parts of color words and noncolor words, and in a baseline condition, of strings of &s (Stroop task). In Experiment 1, the lower part of noncolor words was more ambiguous than the upper part (upward-unbalanced words), whereas in Experiment 2, the ambiguities of the two parts of the noncolor words were similar (balanced words). For the upward-unbalanced noncolor words, the magnitude of lexical interference (relative to the baseline condition) was greater for the upper than for the lower part. Critically, the differences vanished when this factor was controlled (i.e., balanced words; Exp. 2). Thus, the apparent bias in favor of the upper part of words can be parsimoniously described as an idiosyncratic feature of the words' component letters.