Behavioural Neurology (1992),5, 155 -160 JREVIEWJ Empirical. research on deja vu experiences: a review H.N. Sno, H.F.A. Schalken and F. de Jonghe University Department of Psychiatry, Academic Medical Center, Amsterdam, The Netherlands Correspondence to: H.N, Sno, Academic Medical Center, Psychiatric Outpatient Clinic, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands A deja vu experience is a dissociative phenomenon, which can be characterized as a subjectively inappropriate impression of familiarity of the present with an undefined past. This paper reviews empirical studies on deja vu experiences and summarizes the most salient findings. Overall, the findings appear to be inconsistent and inconclusive. The authors conclude that the available empirical research is of limited significance due to various methodological and conceptual issues. In order to evaluate the clinical psychiatric relevance of deja vu experiences, further research which also addresses its qualitative features is warranted. Keywords: Clinical Psychiatry - Deja vu experiences - Dissociative phenomena - Empirical Research INTRODUCTION In 1884 the American psychiatrist Henry Osborn was the periences can occur in any sensory modality and may be first investigator who attempted to gather empirical evi­ viewed as misidentifications of time, place or person. dence concerning what he called "illusive recognition" or Psychopathogetically deja vu experiences can be related "illusions of memory". For this purpose, he distributed a to disturbances or alterations in the normally integrative list of three questions at Princeton University: "Have you functions of identity, memory, perception or attention. come suddenly upon an entirely new scene, and while cer­ Therefore, in terms of the DSM-III-R (APA, 1987), deja tain of its novelty felt inwardly that you had seen it be­ vu experiences may be classified as dissociative phenom­ fore-with a conviction that you were revisiting a dimly ena (Sno and Linszen, 1990; Sno et al., 1992). familiar locality? Mention if you can an instance or two in A subjective phenomenon like the deja vu experience which this has occurred. Has any satisfactory explanation does not permit any experimental approach and the ever suggested itself to you?" Unfortunately Osborn failed research on the subject is consequently almost exclusively to note the number of questionnaires he distributed, nor the committed to empirical studies. To our knowledge only response to them. All he noted of the findings was that three studies have provided some experimental evidence. approximately half the respondents answered affirm­ By means of post-hypnotic amnesia, Banister and Zang­ atively. He proceeded to discuss six characteristic descrip­ will (1941) succeeded to induce the feeling of familiarity, tions given by his respondents and a number of deja vu be it only in three of five subjects. Mullan and Penfield experiences that other authors had written about. On the (1959) reviewed a series of214 patients treated surgically grounds of his findings, he came to the conclusion that for relief of their temporal lobe seizures. In six of these "the rationale of most illusive recognition, then, may be patients, it had been possible to reproduce a deja vu ex­ found in present analogies to the lost mental records of perience by electrical stimulation of the temporal lobe. actual past life, in the former wanderings of our reveries More recently Halgren et al. (1978) reported deja vu ex­ and dreams, or in half conscious trains of thought" periences evoked by electrical stimulation of the median (p.481). temporal lobe with stereotaxic placed depth electrodes in 5 To date these "illusions of memory" are generally of 36 psychomotor epileptics. known as deja vu experiences. These experiences are Ever since the study of Osborn (1884), only a small characterized as any subjectively inappropriate number of authors have attempted to gather empirical evi­ impressions of familiarity of the present with an undefined dence concerning the deja vu experience. The most com­ past (Neppe, 1983). Most people are assumed to have had prehensive studies were performed by Bernard-Leroy deja vu experiences at one time or another. These ex- (1898), Heymans (1904, 1906), Chapman and Mensh © 1992 Rapid Communications of Oxford Ltd Behavioural Neurology. Vol 5. 1992 155 H.N. SNO ET AL. TABLE I. Empirical studies on deja vu experiences Author Year Group studied Gender Number Interview Questionnaire M/F .. ~~,---- Osborn 1884 Princeton University -' -' No Self report Lalande 1893 -' -' 100 Yes No Bernard-Leroy 1898 -' -' 67 No Self report Heymans 1904 Psychology students M 35 No Self report F 10 No Self report Heymans 1906 Psychology students -' 88 No Self report Chapman 1952 Ambulatory and M 110 Yes Observer and Mensh clinical patients F 110 Yes Observer Richardson 1967 Neurosurgical patients M 93 Yes Observer and Winokur F 68 Yes Observer Psychiatric patients M 117 Yes Observer F 184 Yes Observer Harper 1969 Health Dept employees M 24 Yes Observer F 67 Yes Observer Neppe 1979 Members Cultural Society F 84 Yes Observer Neppe 1983 "Normals" -' 28 Yes Observer "Neuropsychiatric" patients -' 48 Yes Observer , Information not provided. (1952), Richardson and Winokur (1967, 1968), Harper The frequency rate was not assumed to be influenced by (1969) and Neppe (1979,1983) (TableI). In this paper we gender, race or social-economic status. Bernard-Leroy did review the studies by these authors in more detail. In the however feel there were indications that age played a role. conclusion, the most salient findings as well as the conse­ On the basis of his interviews, he could not confirm the quences as to future research are discussed. facilitating influence of fatigue, intoxication, infectious disease or emotional states. In his opinion, the influence of The study of Bernard-Leroy (1898) epilepsy was overestimated; none of the 98 epileptic In 1898 Bernard-Leroy, a French psychiatrist, published patients he interviewed at the Salpetriere had experienced his dissertation describing the findings of his research on the phenomenon. Moreover, deja vu experiences did not the deja vu experience. His study was conducted with a prove to occur any more frequently among so-called self-administered questionnaire that had been previously "neuropathic" patients than among so-called "normal" published in an English-language and a French-language individuals. journal. This questionnaire included 36 questions on the frequency of the deja vu experiences, and on predisposing Heymans' studies (1904, 1906) and precipitating conditions. He received only 67 com­ In 1904, the Dutch psychologist Heymans reported the pleted questionnaires, and 49 of these were included un­ findings of a prospective study on deja vu experiences and edited at the end of his dissertation. Due to this low depersonalization. The study was performed by using a response rate, Bernard-Leroy was not able to draw any IS-item questionnaire, with which Heymans attempted to conclusion as to the frequency of occurrence. elucidate characteristic personality traits as well as speci­ In addition to this questionnaire study, a large number fic facilitating conditions. The sample consisted of 35 of subjects were either interviewed by Bernard-Leroy male and 10 female psychology students in the 20-25 age himself or by one of his colleagues. About half of the range. The response rate was 93% and 41 % ofthe respon­ approximately 500 non-disturbed individuals who were dents claimed to have had at least one deja vu experience at interviewed had had deja vu experiences. Of some 60 one time or another. Eight of his respondents reported a patients at the Salpetriere, only six appeared to have total of 13 deja vu experiences during the research period. experienced the phenomenon. Due to incoherence, the Without any verifiable statistical analysis, Heymans reliability of these patients was limited. Bernard-Leroy felt that on the grounds of his data, he could specify four nonetheless concluded that the estimate of 30% by personality traits as predisposing factors: emotional sensi­ Lalande (1893), based on interviews with 100 individuals, tivity, mood fluctuations, periods of apathy and an irregu­ probably came closest to the truth. Based on his own find­ lar working rhythm. In his view, this conclusion was ings, Bernard-Leroy felt he could conclude that a deja vu confirmed by the findings of a replication study published experience was generally accompanied to varying degrees in 1906. The respondents (n = 88) of the 1906 study were by a clearly painful or pleasant effect or by sampled by way of a request in the 1904 article, and from depersonalization. psychology students of a different year's course. This time 156 Behavioural Neurology. Vol 5 .1992 DEJA VU EXPERIENCES the life-time prevalence of deja vu experiences amounted higher occupational level had deja vu experiences more to 63%. Thirty-one of the 88 respondents prospectively often. In addition, people who never traveled had them less reported a total of 94 deja vu experiences. often than frequent travelers: 11 % as compared to To our knowledge, Heymans' study is unique in that it is 24-44%. As regards age and education, a negative and a the only study with a prospective design. The disadvan­ positive correlation were observed respectively. tage of the possible overinclusiveness of this design was refuted by Heymans in advance. He argued that deja vu The studies of Richardson and Winokur (1967, experiences were based on