Stylochronometry with substrings, or: a poet young and old
Rob J Forsyth · Literary and Linguistic Computing · 1999
Assigning a date to a text is an important task in stylometry. Most previous research, however, have worked on intractable problems, where a true chronology will never be known with certainty, such as the works of Plato, Shakespeare or Marlowe. It is argued here that stylochronometric methods should be extensively tested on unproblematic texts before being used in disputed cases. As part of such testing, the present study applies a novel technique, Monte-Carlo Feature-Finding, to the verse of W. B. Yeats, where the dating is relatively well documented. Yeats insisted that his language changed as he grew older, and most readers would concur; yet scholars have not reached agreement on the nature of this linguistic change. A quasi-random search algorithm was used to find markers substrings in 142 poems of Yeats. To test their distinctiveness, four trials were performed: (1) assignment of ten poems absent from the training sample to their correct period; (2) detecting differences in two poems written by Yeats in his twenties and revised when he was fifty; (3) constructing a regression formula; and (4) classifying two prose extracts written forty-six years apart. Assigning short poems (median length 114 words) to their correct chronological period is a non-trivial task. Nevertheless, counting of distinctive substrings gave the right assignment in nine out of ten unseen cases. Moreover, these substring frequencies were sensitive enough to detect authorial revision in two early poems revised by Yeats many years after he originally wrote them, and robust enough to classify a pair of short prose extracts correctly; as well as accounting for 71% of the variance when used in a regression to predict the year in which thirteen poems, absent from the training sample, were composed. These results suggest that short substrings found by a Monte-Carlo process warrant further investigation as stylistic indicators.