Dual-Processing Explanations (Part 2)

Perception and memory

Another dual-process interpretation, proposed by Bergson, is that perception and memory are simultaneous events and that “memory is never posterior to the formation of perception; it is contemporaneous with it. Step by step, as perception is created, the memory of it is projected beside it, as the shadow falls beside the body” (as cited in Carrington, 1931, p. 303; cf. Tulving, 1968). People’s cognitive resources are generally focused on the perception of an ongoing event, but distraction, inattention, or fatigue can lead to memory and perception momentarily enfolding in on each other.

Bergson likened this to two soldiers marching in tight formation: If the first one pauses for a moment, the two will bump into each other. Thus, if storage of information occasionally occurs the moment it is perceived, it could give rise to inappropriate recognition or deja vu.

Dual consciousness

Hughlings-Jackson (1888) suggested that people have two varieties of consciousness: normal, which processes information from the outside world, and parasitic, which monitors the thoughts and reflections of the inner, mental world. When the activity of the normal consciousness is diminished by distraction, fatigue, or seizure (in TLEs), evaluating the familiarity of incoming sensory experiences must depend on the more primitive internal consciousness, which operates from mentally generated images.

The result is a momentary misreading of a new experience as old, leading to deja vu. Rather than dominant and recessive states of consciousness, Wigan (1844) proposed two more equal and coordinated states. Only one is usually operational at any given moment, and it is the occasional activation of the second system simultaneous with the first that results in a déjà vu experience.

Only one brain has been used in the immediate preceding part of the scene—the other brain has been asleep, or in an analogous state nearly approaching it. When the attention of both brains is roused to the topic, there is the same vague consciousness that the ideas have passed through the mind before.

We have no means of knowing the length of time that had elapsed between the faint impression received by the single brain, and the distinct impression received by the double brain. It may seem to have been many years. (Wigan, 1844, pp. 84–85)”

Dual-Processing Explanations (Part 1)

The first category of deja vu explanations is based on a disruption in the normal operation of two separate but interactive cognitive processes. At the core of each speculation, two mnemonic processes that generally operate in concert occasionally become asynchronous, or one process becomes activated in the absence of the other.

Familiarity and retrieval.

Gloor (1990) proposed that retrieval and familiarity are independent cognitive functions that usually operate in a coordinated manner, with recall accompanied by a sense of familiarity concerning the information retrieved. However, these two processes occasionally operate independently of each other. Thus, retrieval can be activated in the absence of familiarity, which causes an ostensibly familiar setting to become momentarily unfamiliar (jamais vu). Conversely, a familiarity response may become activated in the absence of retrieval (deja vu).

This issue is also related to a large literature concerning the possible independence of recall and familiarity (Gardiner & Parkin, 1990; Tulving, 1985) and the process dissociation procedure (Jacoby, 1991).

Encoding and retrieval.

De Nayer (1979) proposed a tape recorder metaphor for deja vu. Under normal conditions, memory encoding and retrieval operate in a manner similar to the record and play heads (respectively) on a tape recorder: Either the record (encode) or play (retrieve) head can be on but not both at once. On rare occasions, the tape machine in a person’s memory has both the record and play heads active simultaneously during a new experience, creating a false sense of familiarity for the newly encoded experience. Though this interpretation is intriguing, it is not well developed and remains at the nascent metaphoric level.

Most cognitive psychologists would assume that retrieval of information (from semantic memory) is an important component of successful encoding. In addition, it appears to be at odds with Pashler’s (1994) research on the bottleneck model of attention, in which a single, central processor is required for memory encoding, memory retrieval, and response selection. From this perspective, encoding and retrieval can never occur in parallel. Furthermore, other models suggest that memory is the outcome of whatever processing occurred during input (Johnson, 1983; Kolers & Roediger, 1984) rather than being attributed to specific encoding or retrieval operations.

Explanations of Deja Vu

For more than a century, researchers have proposed a variety of explanations for the deja vu experience. Many are framed within the psychodynamic and parapsychological perspectives, and the interested reader should consult Neppe (1983e) or Sno and Linszen (1990) for further details on these explanations.

Scientific interpretations of the deja vu experience fall into four categories: dual processing, neurological, memory, and attentional. The dualprocessing explanations assume that two cognitive processes that normally operate in synchrony become momentarily uncoordinated or out of phase. Neurological explanations suggest that deja vu represents a brief dysfunction in the nervous system involving either a small seizure or alteration in the normal time course of neuronal transmission. Memory interpretations assume that some aspect of the present setting is objectively familiar but that the source of familiarity has been forgotten. Finally, attentional interpretations posit that an initial perception under distraction is followed immediately by a second perception under full attention.

With respect to ultimately explaining the deja vu experience, the dual-processing and neurological positions are less useful than the attentional and memory explanations. The dual-processing interpretations have deep historical roots, but they are less clearly and precisely formulated and are grounded more in the theoretical-philosophical than in the empirical realm. The neurological positions are more logically compelling and molecular, but a laboratory test of these explanations may be problematic with today’s technology.

The attentional and memory interpretations of déjà vu make clear connections with current cognitive findings, and a number of possible empirical tests emanates from these two perspectives.

Related Phenomena to Deja

Several other recognition dysfunctions have been related to the deja vu experience. Jamais vu can be considered the opposite of deja vu in that it involves encountering an objectively familiar stimulus that momentarily feels unfamiliar (Burnham, 1903; Conklin, 1935; Critchley, 1989; Cutting & Silzer, 1990; Hughlings-Jackson, 1888; Neppe, 1983e; Reed, 1974; Sno, 2000).

Jamais vu is related to both word alienation, when an ordinary word suddenly looks unfamiliar (Heymans, 1904, 1906; Sno & Draaisma, 1993), and semantic satiation (Amster, 1964; Kounios, Kotz, & Holcomb, 2000), when the repeated (massed) presentation causes a word to momentarily lose its connotative meaning. Jamais vu is much rarer than deja vu (Findler, 1998; Reed, 1974; Sno, 2000), but Heymans (1904, 1906) presented data suggesting that the two recognition dysfunctions of deja vu and jamais vu may be related.

Also related to deja vu is the Capgras syndrome (Capgras & Re ´boul-Lachaux, 1923), a condition in which an individual believes that someone familiar (friend, relative) has been replaced by an imposter. This most studied of the delusional misidentification syndromes does not occur in neurologically and psychiatrically healthy adults but is associated with either schizophrenia or organic brain damage (Critchley, 1989) involving the right hemisphere (Fo ¨ rstl, Almeida, Owen, Burns, & Howard, 1991).

Déjà vu may also be related to reduplicative paramnesia, whereby an individual believes that the present situation is one that has been duplicated from the past (Hakim, Verma, & Greiffenstein, 1988; Langdon & Coltheart, 2000). The typical episode of reduplicative paramnesia involves a hospitalized patient mistakenly convinced that the present hospital is the same one that he or she had been in earlier (in a different geographical location). As with the Capgras syndrome, this recognition dysfunction is confined to individuals with (delusional) psychopathology usually associated with brain injury involving the frontal lobe (Benson & Stuss, 1990) and is unaltered by providing patients with clear evidence to the contrary (Langdon & Coltheart, 2000).

Two other rare misidentification syndromes, Fre ´goli syndrome (Courbon & Fail, 1927) and intermetamorphosis (Courbon & Tusques, 1932), have also been connected with deja vu by Berrios (1995). Both involve the belief that a familiar (intermetamorphosis) or unfamiliar (Fre ´goli syndrome) individual has been replaced by a familiar friend or relative.

Psychopathology of Deja Experience

Some suggest that the incidence of deja vu is more common among people with schizophrenia than among the population in general (Cutting & Silzer, 1990; Kirshner, 1973; Neppe, 1983e; Richardson & Winokur, 1967, 1968). However, it is difficult to determine whether their deja vu experience is similar to that of nonschizophrenic individuals because schizophrenia involves a variety of cognitive distortions (M. A. Harper, 1969). Sno, Schalken, and de Jonghe (1992) suggested that there is a continuum of deja vu, ranging from brief and fleeting in those without to chronic and prolonged in those with schizophrenia.

Taking a more general look at deja vu and psychopathology, M. A. Harper (1969) did not find any general relationship between deja vu frequency and neurotic traits (and phobias) or psychiatric health. In fact, deja vu appeared to be less common in neurotic individuals.

Richardson and Winokur (1968) examined the incidence of deja vu across 10 subtypes of psychopathology (depression, schizophrenia, personality disorder, etc.) and found a higher deja vu incidence only for individuals with personality disorder and situational reaction. They concluded that deja vu might be diagnostic of personality disorder, but the high variability in sample size across subtypes and the problematic sampling procedures make this conclusion suspect.

In a comparison of seven subtypes of neuropathology (brain, meninges, cerebral vessels, spinal cord, etc.), Richardson and Winokur (1968) found no difference in the incidence of deja vu. However, deja vu has been found to be more common in those who have suffered head injury with loss of consciousness (M. A. Harper, 1969) in addition to being associated with amphetamine psychosis (Ellinwood, 1968), influenza medications (amantadine and phenylpropanolamine; Taiminen & Ja ¨a ¨skela ¨inen, 2001), abuse of toluene-based solvents (Takaoka, Ikawa, & Niwa, 2001), withdrawal from medications prescribed for bipolar disorder (carbamazepine, clonazepam; Garbutt & Gillette, 1988), and herpes simplex encephalitis (Yamashita, Yoshida, Yoneda, Mori, & Yamadori, 1994).

Deja Experience by Dreams

Some individuals report that their deja vu experiences appear to duplicate a prior dream, and it is possible that dreams provide the fragmentary memories later duplicated during the deja vu (cf. Baldwin, 1889).

When Zuger (1966) asked his respondents whether they (a) experienced deja vu and (b) remembered their dreams, a striking relationship emerged: All 10 respondents who reported no dream memory also reported no deja vu experiences, and all 36 respondents who reported deja vu also reported remembering their dreams (9 reported dream recall but no deja vu). Thus, there appears to be a strong relationship between remembering dreams and experiencing deja vu. Palmer (1979) discovered a significant correlation between deja vu and dream frequency among older adults but not among college students.

However, the lack of correlation among students may be due to restriction of range because the college group reported a high number of both experiences. Hence, although Zuger speculated that the déjà vu experience is actually a dream state intruding into waking consciousness, it is also likely that dream memory fragments may trigger a deja vu when similar situations are reencountered while awake.

Deja Experience by Stress, Fatigue, Anxiety, and Illness

Earlier anecdotal reports linked deja vu with physical or psychological distress, suggesting that “it occurs most frequently after periods of emotional stress, or in the state of extreme mental fatigue” (Titchener, 1924, p. 187) or “when one is in a let-down state, and far from alert and keen” (Woodworth, 1940, p. 357).

This speculation has received considerable support (Anjel, 1886; Arlow, 1959; Conklin, 1935; de Nayer, 1979; Groh, 1968; Heymans, 1904, 1906; Krijgers Janzen, 1958; Leeds, 1944; MacCurdy, 1925; Murphy, 1951; Oberndorf, 1941; Osborn, 1884; Richardson & Winokur, 1967, 1968; Schneck, 1962; Siomopoulos, 1972; Smith, 1913; West, 1948; Yager, 1989).

In prospective research, Leeds (1944) found that his own deja vu experiences were more likely when fatigued, and Heymans (1904, 1906) noted that fatigue was associated with the majority of deja vu episodes reported by his students.

A further point of interest is Linn’s (1954) assertion that deja vu was frequently experienced by soldiers going into battle. Indeed, marching through new terrain under the heightened stress of anticipating combat may present an ideal set of circumstances for eliciting deja vu experiences. This may also relate to the higher incidence of deja vu in travelers (see Travel Frequency section), as trips are often moderately to highly stressful experiences.