Word Type Frequency Alone Can Modulate Hemispheric Asymmetry in Visual Word Recognition: Evidence from Modeling Chinese Character Recognition

In Chinese orthography, a dominant structure exists in which a semantic radical appears on the left and a phonetic radical on the right (SP characters); the minority, opposite arrangement also exists (PS characters). Recent studies showed that SP character processing is more left hemisphere (LH) lateralized than PS character processing; nevertheless, it remains unclear whether this is due to phonetic radical position or character type frequency. Through computational modeling with artificial lexicons, in which we implement a theory of hemispheric asymmetry in perception that posits differential frequency bias in the two hemispheres (i.e., the DFF theory; Ivry & Robertson, 1998), but do not assume phonological processing being LH lateralized, we show that although phonetic radical position, visual complexity of the radicals, and character information structure may all modulate lateralization effects, the difference in character type frequency alone is sufficient to exhibit the effect that the dominant type has a stronger LH lateralization than the minority type. Further analysis suggests that this effect is due to higher visual similarity among characters in the dominant type as compared with those in the minority type. This result demonstrates that word type frequency alone can modulate hemispheric lateralization effects in visual word recognition.