[Orthographic similarity or semantic relation? The origin of orthographic neighborhood size effects on the lexical decision to Japanese kanji words].

: It is known that lexical decisions to Japanese kanji words get faster as the orthographic neighborhood size of the words grows. This study aimed to show that this facilitative effect of orthographic neighborhood size is due not only to orthographic similarity but also to semantic relationships between words and their neighbors. In the experiment, common and proper nouns each composed of two kanji characters were used as stimuli, the latter having no semantic relation to their neighbors. Lexical decision times for each type of noun were measured with large and small orthographic neighborhoods. The results showed that lexical decision times for both common and proper nouns with large neighborhoods were shorter than those with small neighborhoods, and that the difference was prominent for common nouns sharing their first characters with neighbors. These results suggest that the semantic relatedness of the first characters of Japanese kanji words and their neighbors also facilitates their lexical decision. Finally, variance of neighborhood effects on lexical decision among writing systems and the need to consider various kanji-specific factors are discussed.