In the present study on a review on Kana and Kanji processing, the historical background of psychological studies on Kana and Kanji is described to understand how the interactive activation models were developed as a universal explanation for language processing. The early studies on Kana and Kanji script in the 1960s are discussed in the framework of evolutional theories which focused only on the script capability of phonological representations. In the 1970s, studies of Japanese dyslexia found distinct phonological and orthographic routes to assess the mental lexicon by Kana and Kanji. In the early 1980s, neurological studies revealed that the nature of linguistic tasks resulted in a shift of hemispheric specification. In the late 1980s, psychological studies proposed the intricate model that Kana and Kanji processing interactively involve both phonological and orthographic processing. This further developed in the 1990s as the interactive activation (IA) theory and the parallel distributed processing (PDP) theory.