Parafoveal preview effects in reading: Orthographic uniqueness point as a source of constraint in lexical processing
Is letter information processed in parallel or serially when readers encounter words? Kwantes and Mewhort (1999a; 1999b) addressed this question by introducing the concept of a word's orthographic uniqueness point (OUP). A word's OUP refers to the letter position in a word where that letter pattern uniquely identifies the word. They found faster naming times for words with an early OUP versus words with a late OUP. They argued that the faster naming times for the early OUP words is inconsistent with parallel implementations of models of letter processing. However, the overall letter overlap between the target word and other words that a reader knows was not controlled (Lamberts, 2003) and might account for the differences in naming times rather than for differences in the position of a word's OUP. Readers might be sensitive to any difference in the degree of letter overlap with other words and parallel letter processing accounts could be sensitive to this difference. Two experiments were conducted to extend OUP findings to a more natural reading context by monitoring eye movements while readers read sentences. The first experiment used stimuli with a relatively large difference in the position of a word's OUP. The second experiment matched the early and late OUP words in terms of the overall letter overlap with other words and unconfounded the initial trigram frequency. In both experiments, readers did not benefit from a word possessing an early OUP. The results were discussed in terms of potential serial and parallel letter processing accounts.