Visual and Task characteristics may explain hemispheric asymmetry in visual word recognition

Previous studies proposed that the left hemisphere (LH) lateralization in English word recognition is because of the LH superiority in language processing. Nevertheless, Chinese character recognition has been shown to be more bilateral or right hemisphere (RH) lateralized and thus is a counter example of this claim. Through computational modeling, here we show that at least two factors other than language lateralization may influence hemispheric asymmetry in visual word recognition: (1) Visual similarity among words, which can be influenced by the ratio between the alphabet size and the lexicon size and the visual similarity among letters: We show that the more similar the words are in the lexicon, the more high spatial frequency (HSF) information is required to distinguish them, and this leads to more LH lateralization (2) The requirement to decompose a word into letters in order to map them to corresponding phonemes in pronunciation: We show that letter identity mapping requires more HSF information than word identity mapping, and alphabetic reading requires more HSF information than logographic reading; this leads to more LH lateralization in alphabetic languages. These two visual and task characteristic factors alone may explain differences in lateralization between English word and Chinese character recognition, without assuming the influence from language lateralization.