census of hallucinations

   Also referred to as Census of Waking Hallucinations. Both titles are used to denote the first large-scale survey of hallucinations in the non-institutionalized population, carried out between 1889 and 1892 by the British Society for Psychical Research (SPR). In 1889 the SPR, represented by the Cambridge moral philosopher Henry Sidg-wick (1838-1900), mobilized 410 interviewers in order to investigate 17,000 individuals in the United Kingdom. Reports of * dreams and other non-hallucinatory phenomena were excluded from the investigation, and Sidgwick's committee also weeded out all dubious cases. The results of this cross-sectional survey suggested that 9.9% of the non-institutionalized population in the United Kingdom could remember having had one or more hallucinations. As the committee was particularly interested in signs of life from beyond, Sidgwick et al. focused on reports involving individuals who had died within a time frame of 12 hours before or after appearing in one of the participants' hallucinations. After rejecting all accounts in which foreknowledge ofthe illness or impending death of the person in question could have played a role, the committee was left with 350 first-hand reports of death-related visions. According to the committee, this number was 440 times higher than one would expect on the basis of chance alone. As a consequence, the general conclusion of the committee was that "between deaths and apparitions of the dying person a connexion exists which is not due to chance alone." At the time, similar results had been obtained in Germany by a group headed by Baron Albert von Schrenck-Notzing (1862-1929), in France by the group of Léon Marillier (1862-1901), and in the United States by the American Society for Psychical Research, headed by the philosopher and psychologist William James (1842-1910). The activities of all four groups had been closely followed by the German hallucinations researcher Edmund Parish (1861-1916), who absorbed their preliminary reports as soon as they appeared, and published these in his book Ueber die Trugwahrnehmung (Hallucination und Illusion). Parish's book appeared in 1894, a few months before the SPR's final Report on the Census of Hallucinations was published. It contains a meta-analysis of the material from all four groups, indicating that the combined research units had received a total of 27,329 answers from their respective target populations, of whom 11.96% on average were found to be familiar with hallucinations. Subsequent studies, carried out throughout the 20th century, roughly replicated the epidemiological findings of the SPR and their sister organizations, showing that this number had not been exaggerated. What does seem to have changed during the intervening century, however, is the prevalence of * visual hallucinations (which had been found to be higher in the earlier studies) and * auditory hallucinations (which had been found to be lower in the earlier studies). This may be a reflection of genuine change, as the American psychiatrist and epidemiologist Allen Y. Tien speculates, but it is also possible that it reflects selection bias on the part of the SPR investigators. After all, they had been free to select participants from the population at large, and they were known to have a vested interest in tracking down so-called *veridical or Coincidental hallucinations involving dead or dying people, which were thought to be mainly visual in nature. The metaphysical implications of the SPR's findings were criticized by Parish, and by many others after him. In present-day scientific references to the Census of Hallucinations they tend to be ignored altogether. However, the SPR's epidemiological findings are still widely cited.

   References

   Parish, E. (1894). Ueber die Trugwahrnehmung (Hallucination und Illusion). Leipzig: Verlag von Ambrosius Abel.

   Sidgwick, H., Johnson, A., Myers, F.W.H., Podmore, F., Sidgwick, E. (1894). Report on the census of hallucinations.In: Proceedings of the society for psychical research. Volume XXVI. Part X. London: Kegan Paul, Trench, Trübner & Co.

   Tien, A.Y. (1991). Distributions of hallucinations in the population. Social Psychiatry and Psychiatric Epidemiology, 26, 287-292.