  Word frequency is assumed to correlate with word familiarity, but the
strength of this correlation has not been thoroughly investigated. In this
paper, we report on our analysis of the correlation between a word familiarity
rating list obtained through a psycholinguistic experiment and the
log-frequency obtained from various corpora of different kinds and sizes (up to
the terabyte scale) for English and Japanese. Major findings are threefold:
First, for a given corpus, familiarity is necessary for a word to achieve high
frequency, but familiar words are not necessarily frequent. Second, correlation
increases with the corpus data size. Third, a corpus of spoken language
correlates better than one of written language. These findings suggest that
cognitive familiarity ratings are correlated to frequency, but more highly to
that of spoken rather than written language.
