Dating Dickinson: an Experimental Approach to Stylochronometry

Stylometry is the statistical analysis of literary style, whose two primary applications are authorship attribution and chronological problems. It originated in 1851 when Augustus de Morgan suggested that it is possible to settle authorship by determining if one text "does not deal in longer words" than another (Holmes, 1998). Stylometry is based upon the notion that it is possible to detect an author's 'signature' by examining quantifiable features of written texts. The only difference between the two applications is that attributional studies claim that certain features in an author's style are manipulated unconsciously and therefore remain fixed, whilst chronological studies support the idea that stylistic fingerprints evolve smoothly throughout an author's life. The contradiction is overridden, though, by the choice of features.

Stylochronometry, a term used to cover the dating of texts from stylistic evidence, concerns itself with problems of specifying the sequence of composition of the works of a given author. Famous cases are the dating of Plato's dialogues, of certain of Shakespeare's plays, and the dating of the New Testament scriptures, although their true chronology will never be known since there is not enough external evidence to back up such stylometric findings.

Scientific approaches to chronology begin with the choosing of a group of texts that are more or less securely dated, then proceed with the application of stylometric methods that manipulate the chosen variables which will best correlate with the dates of the texts. Once the methods used assign the correct dates to the initial test set, the final step is to employ the same methods on disputed cases. Such stylometric variables include high frequency words, function and common words, type-token ratio, vocabulary richness measures and others.

A famous example comes from Brainerd (1980) on the chronology of Shakespeare's plays. Examining the percentage of occurrence of 120 lemmata, which were mainly related to high-frequency lexical items, additionally combined with the investigation of the average verse line length in words, the percentage of split lines and the type-token ratio, he concentrated initially on a group of plays that had fairly accurate dates of composition. Since only 20 out of the 120 lemmata proved to be useful discriminators for chronology, he used them in order to construct a function that would predict the dates of the control group. Once his method produced the desired results, the final step was to use it on those of Shakespeare's plays which were of disputed nature in terms of dates. Difficulties arose related to the possibility of multiple authorship in certain cases, authorial revision at some stage, and the status of manuscripts used for the preparation of the basic copy texts. However, multivariate statistics proved useful in order to detect which plays were likely to be products of multiple authorship.

In poetry though, it has not been possible to date texts of less than 500 words in length until recently. Forsyth (1999) at BSRU investigated a method of dating short pieces of text (averaging 114 words in length) and tested them on W.B. Yeats's work. This method, among others, will be used in our project, which aims at building on collaborative work begun by Dr Forsyth and Prof. Margaret Freeman of Valley College, California, on the investigation of chronological changes in the style of the American poet Emily Dickinson (1830-1886).

Born in Amherst, Massachusetts, Dickinson lived at her father's house most of her life and in her later years became a recluse. Because of her individualistic style, which, as it is accepted nowadays, set her ahead of her time, only 10 of her poems were published during her lifetime. Moreover, due to her difficult handwriting and her idiosyncratic punctuation, they were heavily edited, since the public was not yet prepared for her eccentric masterpieces. At the time of her death, 1775 poems were discovered arranged in 60 small packets. Following that, efforts were made by her relatives to get all the poems published; still, though, her poetry was heavily edited. Her impact on the American public gradually became intense, and in 1955 a complete edition of her work was published by Thomas H. Johnson, this time using her own punctuation and vocabulary. Today she is known for her startling originality, her bold experiments in prosody, her tragic vision, and the range of her intellectual and emotional explorations.

Johnson's edition provides approximate dates of composition (Johnson, 1961), according to Theodora Ward's study, who collaborated with Johnson, of the changes in her handwriting, apart from a few poems which have precise dates, either because Dickinson sent them as parts of letters to various friends or because she mentions contemporary events.

Our investigation will initially concentrate on control authors that have securely dated works, such as Christina Rossetti and W.B. Yeats. Both poets lived in the 19th century as Dickinson did. It is proposed to utilise a feature-finding program developed by Forsyth & Holmes (1996) at BSRU, a tagger such as TOSCA from Nijmegen University, and a content analysis tool. Thus we will tap into linguistic information of different kinds - lexical, syntactic and semantic. Our aim is to detect the type of linguistic information that is useful for discriminating between the early and late works of our poets with the intention of using the techniques applied on the control authors to date Dickinson's work.

Laan (1995) argues that there is no hard evidence to suggest that authors have both a conscious and an unconscious aspect to their writing style, as stylometry suggests. On the other hand, possibilities such as the existence of a stable and an adaptable part in an author's unconscious style, or the idea that some change their unconscious features of their styles and others do not, also exist as Laan (1995) admits. The question to what extent such claims are true has been investigated by Robinson (1992) and Keyser (1992) who both suggest proceeding from authors with known publication dates to authors with unknown publication dates.

Initial studies, to be reported at this conference, have investigated the idea that authors generally exhibit a trend towards decreasing complexity as they grow older. Using the Fog Index as a measure of the density of language, based on the proportion of long words and average sentence length, we have found equivocal results. But other measures do seem to show increased simplicity with time. We believe that this brings us a step closer to correct chronology.

References

Brainerd, B. (1980) "The Chronology of Shakespeare's Plays: A Statistical Study". Computers and the Humanities 14, 221-230.
Forsyth, R. S. (1999) "Stylochronometry with Substrings Or: A Poet Young and Old". Literary and Linguistic Computing. 14(4), 1-11.
Forsyth, R.S and Holmes, D.I. (1996) "Feature Finding for Text Classification". Literary and Linguistic Computing. 11(4), 163-174.
Holmes, D. I. (1998) "The Evolution of Stylometry in Humanities Scholarship" Literary and Linguistic Computing. 13(3), 111-117.
Johnson, T.H. (ed) (1961) The Complete Poems of Emily Dickinson. Little, Brown and Company, Boston.
Keyser, P. (1992) "Stylometric Method and the Chronology of Plato's Works (review article)".Bryn Mawr Classical Review. 3(1), 58-74.
Laan, N.M. (1995) "Stylometry and Method: The Case of Euripides". Literary and Linguistic Computing. 10(4), 271-278.
Robinson, T.M (1992) "Plato and the Computer". Ancient Philosophy. 12, 375-382.