Conclusions

Deja vu is experienced by a majority of the population, and occurs about once a year in experients. The incidence decreases with age but increases with education and socioeconomic class.

Deja vu is more common under conditions of stress and fatigue, and it is experienced more frequently by persons who travel.

Societal acceptance of the phenomenon appears to have increased over recent decades. Though deja vu historically has been linked to temporal lobe epilepsy and schizophrenia, this association has not been convincingly demonstrated.

Explanations of the phenomenon have included (a) momentary alteration in the normal operation of two usually coordinated cognitive processes; (b) neurological dysfunction (seizure, slowed synaptic transmission); (c) implicit memory activation based on familiarity of processing, object, or gestalt configuration; and (d) unattended perception (under distraction) followed immediately by a fully aware perception.

Although the deja vu experience occupies a solid position in the popular culture, the community of research psychologists has been largely silent on the topic. It is hoped that the use of more sophisticated research techniques to help elucidate this illusion of recognition will change this situation and that the findings from such research efforts could expand the field’s understanding of routine memory functions. As Roediger and McDermott (2000) suggested, “distortions of memory provide a fertile ground for studying interesting and important psychological phenomena” (p. 123).

Attentional Explanations (Part 3)

Inattentional blindness

Related to this interpretation of the deja vu, recent research suggests that individuals often miss objects that are clearly visible if they are focused on some other object in the visual array. This inattentional blindness, extensively investigated by Mack and Rock (1998), could explain how an initial brief perception of objects in a scene can go undetected.

When an extraneous visual stimulus (e.g., shape, object, word) accompanies a target stimulus (e.g., cross) to which the participant is instructed to respond (e.g., Which line of the cross is longer?), the individual often misses seeing the extraneous stimulus. When the target stimulus is in the periphery and the extraneous (ignored) stimulus is in the center of the visual field (fovea), inattentional blindness is more likely than when the target stimulus is in the fovea and the extraneous stimulus is in the periphery. Individuals who fail to report the extraneous (e.g., word) stimulus still process it, as reflected in significant priming on a subsequent word stem completion task (Mack & Rock, 1998).

Such a paradigm, in which the stimulus is above threshold but unattended (rather than subthreshold), better models people’s natural perceptual experience (Merikle et al., 2001) and provides a more realistic framework for studying the deja vu experience. For example, one may enter a room talking on a cell phone or thinking about an upcoming meeting while looking directly at a particular stimulus, and moments later this same stimulus is consciously perceived and elicits a déjà vu. Perhaps one of the most blatant examples of inattention to suprathreshold stimuli is the “time gap” experience, in which one’s entire perceptual experience over several minutes (e.g., during highway driving) is unrecallable (Reed, 1979).

It is possible that an inhibitory mechanism underlies the inattentional blindness effect. In elaborating on Poetzl’s (1917/1960) earlier speculation, N. F. Dixon (1971) suggested that during an initial brief stimulus exposure there is “a rapid fragmentation of the sensory information, wherein ‘inhibition by interference’ causes parts of the stimulus field to interfere with the development of other parts” (p. 106). Thus, certain elements in the stimulus array may suppress or block the perception of other elements, similarly to lateral inhibition in the visual system (cf. Martindale, 1981). In a second glance at the scene immediately after the first, the initially inhibited portion of the visual scene is disinhibited and now matches the present perception. The possibility that inhibition–disinhibition underlies deja vu is supported by the fact that both inhibitory processes and deja vu frequency decrease with age.

The magnitude of negative priming interference, for which a response which is actively inhibited on one trial is more difficult to generate on the immediately succeeding trial, is much smaller with older than younger adults (Hasher, Stoltzfus, Zacks, & Rypma, 1991). If the visual inhibition of parafoveal elements similarly decreases with age, this would reduce the likelihood that inhibited features would later disinhibit and lead to a deja vu.

Attentional Explanations (Part 2)

Perceptual fluency

This model for the déjà vu experience was evaluated by Jacoby and Whitehouse (1989), who discovered that when a test word was briefly presented (and masked) at subthreshold levels immediately prior to presentation on a recognition test, individuals were more likely to call the word “old” compared with a word not briefly preceded by itself. They attributed this illusion that the word had occurred on a prior list to its facilitated processing (perceptual fluency) engendered by the immediately prior subliminal presentation. This fluency bias supposedly precipitates the common experience of having a word appear to “jump out from the page” when reading (Jacoby & Dallas, 1981, p. 333).

Similarly, when a primed perceptual element suddenly and forcefully stands out, and source identification is lacking, this may precipitate a déjà vu. Jacoby and Whitehouse related this finding directly to the deja vu phenomenon, but the paradigm is lacking the element of “this could not have happened here before.” In this type of experimental setting, participants logically can misattribute the word to having occurred in the prior experimental list rather than being convinced that they could not have experienced this word before.

There has been debate over whether participants in this particular paradigm are consciously aware of the masked prime word (Bernstein & Welch, 1991; Joordens & Merikle, 1992; Watkins & Gibson, 1988), but this issue does not undermine the potential relevance of this paradigm for modeling the deja vu phenomenon. In fact, a supraliminal perceptual experience corresponds to Titchener’s (1928) illustration above, and modifying the Jacoby-Whitehouse design to have a divided attention manipulation, rather than subliminal presentation, may better model the deja vu experience. Merikle, Smilek, and Eastwood (2001) summarized the literature on perception without awareness and indicated that there are numerous investigations that suggest that stimuli presented either subliminally or supraliminally (but unattended) consistently have a potential to influence subsequent behavior.

Attentional Explanations (Part 1)

The fourth framework for interpreting déjà vu is that an ongoing stream of perceptual experience is divided into two separate perceptions through distraction or inattention. A brief initial perception of a scene under diminished attention is followed immediately by a second perception under full attention. The second impression matches that experienced moments earlier under degraded attention, and the individual does not consciously identify the prior experience as moments old but rather attributes it to a more distant past. Many researchers have espoused different versions of this interpretation (Conklin, 1935; Heymans, 1904; Lalande, 1893; Osborn, 1884; Wigan, 1844), and Titchener (1928) provided the following, oft-cited illustration:

You are about to cross a crowded street, and you take a hasty glance in both directions to make sure of a safe passage. Now your eye is caught, for a moment, by the contents of a shop window; and you pause, though only for a moment, to survey the window before you actually cross the street. . . . The preliminary glance up and down, which ordinarily connects with the crossing in a single attentive experience, is disjointed from the crossing; the look at the window, casual as it was, has been able to disrupt the associative tendencies. As you cross, then, you think “Why, I crossed this street just now”; your nervous system has severed two phases of a single experience, both of which are familiar, and the latter of which appears accordingly as a repetition of the earlier. (pp. 187–188)

Leeds (1944) called this phenomenon split-perception and proposed that an eye blink could possibly divide these two successive perceptions. Mayer and Merckelbach (1999) even suggested that this type of double take may be part of routine perception. The first second of information processing may be a platform from which a “quick and dirty” unconscious processing can have important effects on subsequent reactions to the stimuli around us. Though Mayer and Merckelbach related their speculation to anxiety disorders, their ideas have clear relevance to the déjà vu phenomenon.

Finally, Krijgers Janzen (1958) speculated that an initial and unattended eidetic image matches a regular perception moments later. He argued that all people experience eidetic imagery occasionally and that regular eidetic imagers would experience déjà vu more frequently than individuals who have eidetic images infrequently.

Memory Explanations (Part 5)

Gestalt familiarity

When the overall perceptual configuration of the present stimulus array is similar to one experienced previously, this gestalt correspondence could trigger a deja vu (Reed, 1974). Recall the example of the first visit to a friend’s home as an illustration; it is not the grandfather clock in the corner of your friend’s living room that is familiar, rather the familiarity comes from the fact that the room has a layout similar to the one in your aunt’s house: a sofa to the right of the love seat with a stairway to the left going up the wall, a grandfather clock against the back wall, and an Oriental rug on the floor. None of the elements in the newly entered living room is identical to one from the previous context, but the particular configuration of elements fits the same template. Sno and Linszen (1990) suggested that different scenes and individuals often overlap in many structural details, and when perception is degraded the general framework of a prior experience may overlap considerably with the present one. Using similar logic, Levitan (1969) suggested that in recognizing an entire scene or setting, people automatically break it down into simpler perceptual forms such as cubes, triangles, circles—a process similar to what cubist painters did. This is also related to Biederman’s (1987) notion that all perceptual experience can be reduced to a relatively small set of geons, which represent the range of all primitive perceptual forms. Thus, the untoward sense of familiarity eliciting deja vu in an unfamiliar setting may arise because the arrangement of the reduced perceptual forms matches those from a prior experience.

Gloor (1990) also used this gestalt analogy and tied his speculation to deja vu experiences in the preseizure aura of TLEs. Drawing on the parallel distributed processing model of Rumelhart and McClelland (1986), Gloor suggested that the erratic firing of neurons in the temporal lobe prior to the seizure gives rise to spurious matches between the present visual scene and prior visual experiences. For both Sno and Linszen (1990) and Gloor, perceptual degradation was more likely to precipitate such configural matches. Assuming that fatigue or stress are associated with such reduced perceptual precision, this fits with the earlier suggestion of an association between fatigue and deja vu.

Memory Explanations (Part 4)

Single-element emotional association

Another framework for interpreting a deja vu is that some aspect of the present situation triggers an affective response which then elicits a deja vu. Under this interpretation, the strange feeling accompanying a deja vuis not elicited by the unsettling contrast between implicit familiarity and explicit source memory failure. Instead, the feeling is evoked by a conditioned emotional association to a particular stimulus.

Under most circumstances, a person can identify the particular stimulus (seeing a person, hearing a name, smelling a perfume) that elicits an emotional reaction. When this implicit emotional reaction cannot be connected to its source, the person misidentifies the emotional arousal as familiarity to an unfamiliar setting and a deja vu results (Pagliaro, 1991; Siomopoulos, 1972). Thus, the implicit affective (emotional) response is immediately reinterpreted in a cognitive (familiarity) manner. To illustrate, imagine you enter a hotel you have never been in before, and a couch in the corner of the lobby is identical to one that was in your grandparents’ house. You experience a strong implicit (and positive) emotional reaction to the item of furniture without explicitly recognizing the item as the source of your affective response. Baldwin (1889) suggested that the emotional reaction must reach a certain level of intensity before it forces the inappropriate feeling of familiarity, and Siomopoulos (1972) speculated that implicit emotional associations to objects may persist long after conscious recollection has disappeared. In support of this possibility, Johnson, Kim, and Risse (1985) demonstrated that in patients with Korsakoff’s amnesia, an affective response to a stimulus could be acquired in the absence of explicit memory.

MacCurdy (1928) speculated that there are always two components of a nominal recognition response: an initial affective reaction, followed immediately by the familiarity (cf. Zajonc, 1980). Although these two stages usually follow in quick and seamless succession, and are essentially indistinguishable as separate processes, deja vu results when the initial affective stage is not succeeded by a clear second-stage memory match. Fleminger (1991) similarly suggested that the affective and cognitive channels of information processing usually work in concert but that deja vu results from “aberrant activity in the pathway responsible for affective interpretation of percepts” (p. 1418). Linn (1953) further speculated that it is not an affective response, in general, that triggers a deja vu. Rather, anxiety evoked by some aspect of the present situation disrupts the normal functioning of the reticular activating system. Thus, Linn (1953) assumed that a change in arousal precipitates a deja vu, rather than a specific affect associated with a stimulus.

These emotion-based interpretations of the deja vu experience are related to the subliminal mere exposure research, in which unfamiliar stimuli exposed at levels well below perceptual threshold (i.e., 5 ms) are later preferred over nonexposed stimuli even though participants are unable to recognize these exposed stimuli as old (Bornstein, 1992; Kunst-Wilson & Zajonc, 1980). In fact, Seamon et al. (1983) specifically related their research on subliminal mere exposure to deja vu:

In deja vu, stimuli are recognized as familiar without recognition of the basis of their familiarity. Essentially, the same outcome was observed in this study: people liked familiar stimuli without recognizing the basis for their familiarity. In this respect, the finding of target selection by affect in the absence of recognition is similar to the well-known, but poorly understood, phenomenon. (p. 188)

This parallel with subliminal mere exposure may be strained because what is typically measured in this research is preference or liking—a modest affective response, at best. What is needed is a way to experimentally evoke the type of intense affective reaction characteristic of a deja vu. Both number of exposures and test delay are directly related to preference (Bornstein, 1989), so perhaps a large number of subliminal exposures and long input-to-test delay could intensify the affective response to a level capable of eliciting a deja vu.

Memory Explanations (Part 3)

Extending the single-element position in a different direction, Sno and Linszen (1990) proposed a holographic explanation of deja vu (see also Meurs & Fies, 1993). If memories are stored as holograms (cf. Pribram, 1969), then each memory involves a unique pattern of neural activation involving the entire cortex. That is, a memory (first kiss, favorite song) is not based on physical storage but on a unique wave form pattern of neural activation. If any perceptual element in a new scene overlaps with an element of a previous memory, then this has the potential to reactivate the entire old memory (Kafka, 1989). If only the implicit familiarity component of that prior experience is reactivated, a deja vu results. However, if both implicit and explicit components are reactivated, the present setting simply reminds the person of a prior experience.

The single-element interpretation of a deja vu is also related to the Poetzl (1917/1960) phenomenon, in which elements of a briefly presented stimulus appear later as a response in an unstructured generation task such as free association, day dreaming, or doodling (cf. N. F. Dixon, 1971). Whereas later extensions of this research evaluated a psychoanalytic theory of dreams, Poetzl’s work was experimentally oriented and involved subthreshold presentations of simple stimuli, or brief suprathreshold presentations of complex visual scenes. The Poetzl phenomenon occurs when these stimulus elements are not immediately accessible (remembered) but appear later in subsequent free associations to word or pictorial stimuli (Allers & Teler, 1924/1960; Erdelyi, 1970; Haber & Erdelyi, 1967; Shevrin & Fritzler, 1968; Silverman & Silverman, 1964). Although usually evaluated through recall procedures, the Poetzl phenomenon could occur with recognition as well, and could underlie the deja vu experience.

The above interpretations focus on a single element; however, it is possible that several familiar elements are involved in a déjà vu experience (Findler, 1998; Fleminger, 1991; Wohlgemuth, 1924). Wohlgemuth (1924) presented an extensive analysis of a personal deja vu experience and found that three elements in the setting duplicated aspects of three separate episodic memories. He speculated that these multiple single elements summated to create an unusually strong feeling of familiarity, whereas none of the individual elements’ contextual associations was sufficiently strong to reach threshold, or competition among the separate contextual associations blocked access to any specific episodic memory. This mechanism is similar to that proposed by Hintzman (1988) in his MINERVA model of memory.