This study examined the difference between authors and the consistency in each author's writing styles, both were the basis of authorship verification. We analyzed 88 academic papers on psychology written by 22 authors and focused on the rates of “non-content words”, “bigram of parts-of-speech”, “bigram of postpositional particles”, “positioning of commas”, ”words before period”, and “Kanji, Hiragana, and Katakana” in the papers. Next, symmetric Kullback-Leibler divergence distances between the papers were calculated. To examine the author differences in writing styles, using hierarchical Bayesian modeling, we compared the distances between papers written by the same author with those by different authors. Furthermore, to examine author consistency in writing styles, we compared the distances of short durations (under five years) between papers written by the same author with the longer durations (over five years). These results supported the hypothesis that there exist author differences and consistency in writing styles.