Reading Cusum Graphs and Charts
The principle on which cusum analysis is based is thus extremely simple, being predominantly based on unconscious, habitual use of function words. The practise is within the grasp of any academic prepared to devote the necessary time and effort to learning it; but, to sound a cautionary note, this would be no rapid process with automatic results. Learning how to use the method with confidence takes about three to six months of practise on a wide variety of texts. By starting with the analysis of one's own utterance (as providing samples of known integrity, a crucial proviso), any researcher is enabled to gain confidence in the effectiveness of the method. The benefit of "tutorials" from experienced analysts is also important. Only then may one approach one's literary problem.
It should be noted here that there have been various attempts at critiques of cusum analysis: these have all failed in remarkably similar ways, namely, by misunderstandings of both principle and practise. One misunderstanding is the notion that the method is based on a single invariable language habit (counting words of 2 or 3 letters is the one usually selected), which is suitable for all writers/speakers and occurs in rigid proportions or ratios in each sentence—an obvious absurdity. There are, in fact, nine language-habit tests used on any sample under analysis to discover which one will be consistent for the writer; and these are counted in no simple proportional manner. Analysing for Authorship devotes a whole chapter to "Answering the Critics", and each critique is carefully examined there. Despite fairly widespread awareness of the few critical attempts, there is complete ignorance of the endorsement of the method's validity by the statistician responsible for writing the British Standard on cusums—who, further, developed a refinement which enhances the original method for the satisfaction of professional statisticians.[19]
One impression of the method's "unreliability", apparently widespread and also described in the book, deserves special mention here since it involves an interview with Morton by a television company who had asked for two samples of writing to be analysed for homogeneity. Given Morton's opinion that they were indistinguishable, the interviewer then dramatically revealed that they were by a man convicted of corporate crime, and by the Lord Chief Justice (Taylor). In actual fact, the "crook" was reading out a company report compiled by his department so that the sample was not his own utterance at all; moreover, the TV crew had got hold of a sample of writing by the wrong Lord Taylor![20] As always, the integrity of the text is everything. Given corrupt data, "wrong" answers will be inevitable: in computer jargon, "garbage in, garbage out". In Morton can be faulted, it is surely in accepting too readily samples whose origin he had not personally been able to verify. But to the viewing public, it apparently seemed Q.E.D. and remains so among some academics
in the attribution field to this day, even if it calls for a certain naïvety to believe that scientific validity can be decided by a ten-minute TV stunt. The old "I saw it in the newspapers" seems to have been superseded by the new "I saw it on TV".
Less well-remembered (or known at all) are the many blind tests where the technique has been successful, some of them required by the presiding judge in a court case. The most amazing example of these is perhaps the one where the "challenger", or person setting the test (Sir Kenneth Dover),[21] did the counting himself and passed over only the resulting numbers—not the Greek text—to Morton. Morton promptly discovered the inserted passage.
Properly used, cusum analysis is a useful tool. A major advantage of the method is that the results of analysing quite small samples can be visually demonstrated in graphic charts which may be understood by the non-expert (for example, a juror in a court case). As well as resistance to computers, there can also be an in-built resistance among literary professionals to looking at graphs. Yet a graph is only a way of presenting information. The more familiar we become with pictorial ways of interpretation, the easier it becomes to "read" the information in that form. How naturally we can now read, for example, television weather maps: "See those isobars packed in tightly together", says the TV Weatherperson, and we know we are in for a spell of high winds.
The sample of utterance under investigation is counted, by cumulative sum (hence, cusum), first for sentence length and the deviation of each sentence in the sequence from the average. The second step is to count, again by cumulative sum, some feature, usually called the "habit", of language-use within the sentence. The nine tests available to the analyst are based on function words, as already described. This is not the place to explore why such features have been found to work, although speculation is intriguing.[22] We need only point to the success of the method in analysing: natural utterance, both written and spoken; edited text; translated work; children's writing; dialect; and disputed utterance. Here we have an attributive measure of great sensitivity which is objective and which works across both time of authorial composition, and genre.
The last claim is one which has occasioned a degree of scepticism, and it is as well to outline the obstacles which must be overcome and habits of mind which must be set aside before the technique can gain confident acceptance by literary scholars. The cusum technique has nothing to do with style or literary value. It is purely quantitative, not qualitative (remember now those assumptions that statistics were analysing style?). Therefore, such procedure as comes naturally to the literary critic, that is sensitivity to tone, image, rhythm; comparison of like with like in terms of genre or date of composition; the difference between poetry and prose—all these must be set aside to turn instead to a study of language by measurable units, and that
unit normally the sentence. Whatever the soundness of the literary/stylistic judgments brought to bear on the
Elegye by Professor Vickers or others, such judgments will remain interpretative rather than objective—indeed, a "game" to some readers. That is why it is worth drawing attention to a method which asserted five years ago that the
Elegye had nothing to do with Shakespeare.
