Shrinkage of the mental lexicon of kanji in an elderly Japanese woman: the effect of a 10-year passage of time.

This investigation addressed the questions at what rate and how an elderly Japanese woman, AA, lost kanji nouns between the ages of 83 years and 93 years. Results from a kanji naming task given twice with a 10-year interval showed that (1) on average, the size of AA's mental lexicon of kanji shrank at a rate of approximately 1% per year and (2) while ease of acquisition had the highest correlation with naming performance followed by kanji frequency, age of acquisition, and visual complexity in this order, a logistic regression analysis identified ease of acquisition and age of acquisition as potent independent variables. Results of error analysis indicated that visual encoding errors were most prevalent. The decline in AA's mental lexicon is discussed in light of the rates of declines in object naming ability reported in previous studies. The concept of ease of acquisition and the dissociation between AA's general mental state and lexicon of kanji are also discussed.