Changing language in Harold Wilson's Commons speeches indicates cognitive deterioration during his final term of office
The motives behind Harold Wilson's resignation as British Prime Minister in April 1976 have long been a source of controversy. Now, a linguistic analysis of his performance at the dispatch box suggests that the earliest stages of Alzheimer's disease may well have contributed to his decision, according to a study just published online in the Journal of Neurolinguistics.
Dr Peter Garrard of the University of Southampton - who previously demonstrated the presence of Alzheimer-like linguistic changes in the later writings of Dame Iris Murdoch - analysed vocabulary trends in transcripts of Prime Minister's question time during Wilson's first, second and final terms in office.
Dr Garrard, who is Reader in Neurology at the University of Southampton's School of Medicine, explains: "Language is known to be vulnerable to the earliest stages of Alzheimer's disease, and the findings of the earlier Iris Murdoch project confirmed that linguistic changes can appear even before the symptoms are recognised by either the patient or their closest associates.
"If such changes are apparent during the effortful and relatively controlled process of creative writing, then the cognitive demands of spontaneous speech production make it even more likely for them to be detectable in spoken output."
Very few records of spontaneous spoken language are preserved for retrospective analysis, but Hansard was one obvious example of such a source. Although many of the contributions to Parliamentary debate are composed in advance and read out rather than delivered extempore, the verbal cut and thrust that follows a Prime Minister's response to a tabled question does not follow a written script.
Transcripts were copied from bound volumes of Hansard and converted to digital format using optical character recognition software. Markers were inserted into the digital text to indicate both the date and the speaker of each contribution, revealing the number of times each word was used by a speaker during the three periods studied. This unique dataset was used to make statistical comparisons between Wilson's language and that of his parliamentary colleagues.
The analysis was based on techniques developed by literary scholars for quantifying the stylistic similarities and differences between authors, genres, and literary eras. The findings confirmed that the content of Wilson's speeches was identifiably different from those of other members of the House in all three periods (as would be expected), but that this difference was smaller during the months leading up to his resignation.
"The results of this preliminary analysis show that significant changes are detectable in archived language samples, using simple measures that can be made rapidly and automatically using digitised texts," continues Dr Garrard.
"Further work is needed to pinpoint the onset of change with more precision, and to demonstrate that the change is genuinely related to the linguistic markers of early dementia.
"Demonstration of a reliable marker, or 'signature', of incipient dementia in spontaneously produced language will be a powerful tool for understanding the evolution of Alzheimer's disease and the human brain's capacity to compensate for its effects."
Last week the Medical Research Council endorsed the importance of this project by the award of a major research grant to Dr Garrard and Dr Celeste de Jager, a neuropsychologist at the University of Oxford. The research team will collect and examine a large database of spoken and written language samples collected over the past twenty years as part of the Oxford Project to Investigate Memory and Aging (OPTIMA). Any new texts submitted by members of the general public and from OPTIMA participants will be of particular interest: suitable material could include letters, diaries and other material written by people with progressive late-life cognitive decline and by those who remained cognitive healthy throughout old age.