Memory Explanations (Part 2)

Single-element familiarity

A deja vu experience may be triggered by one element of the present setting that is objectively familiar but unrecognized because it is experienced in a new and changed context. The familiarity elicited by the one unidentified object is misinterpreted as a response to the entire setting, resulting in deja vu. To illustrate, suppose that you visit a friend’s home for the first time, and the grandfather clock in the corner is identical to one in your aunt’s home. While you experience a familiarity reaction to this element, you are unable to connect your response to the “old” object and misattribute the familiarity to the entire new setting, resulting in a deja vu. This interpretation was proposed in earlier writings on the deja vu experience (Banister & Zangwill, 1941a; Boirac, 1876; Boring, Langfeld, & Weld, 1935; Bourdon, 1894; Conklin, 1935; Humphrey, 1923; James, 1890; Lapie, 1894; Leeds, 1944; Oberndorf, 1941) and has been resurrected in more recent speculation (Jordan, 1986; Levitan, 1969; Reed, 1979; Sno & Linszen, 1990; Zeidenberg, 1973).

MacCurdy (1925) called this phenomenon restricted paramnesia: the experience in which an element of the present setting is familiar but its prior identity is obscure. Banister and Zangwill (1941a, 1941b) used hypnotic suggestion to test this notion that a previously encountered but “forgotten” stimulus can be misidentified as familiar. They did not intend to create a deja vu, but wanted simply to evaluate whether participants could misattribute a hypnotically forgotten stimulus to the wrong setting. On the first day, participants studied pictures and odors during a normal waking state. On Day 2 they were hypnotized and presented with additional picture and odor stimuli, followed by a posthypnotic suggestion to forget these Day-2 stimuli. On Day 3, participants were tested with a mixture of new and old stimuli, and most participants (3 out of 5) misidentified some Day-2 stimuli as having been presented on Day 1. Although Banister and Zangwill (1941a, 1941b) emphasized that their study supported the possibility of such paramnesias, they noted that the relationship between their study and deja vu was “conjectural” and said that the results “throw little light on the origin of deja vu” (Banister & Zangwill, 1941b, p. 51). Despite this disclaimer, hypnotic procedures may hold some promise for an experimental paradigm to elicit déjà vu if accompanied by a sufficiently unique context within which to later experience the subsequently forgotten stimuli.

Also related to the single-element hypothesis is Whittlesea and Williams’s (1998) extension of the processing fluency theory of familiarity. Jacoby and Dallas (1981) demonstrated that when information is reexperienced, it is processed more easily and rapidly than in the first encounter, and this fluid reprocessing gives rise to a sense of oldness concerning the stimulus. Whittlesea and Williams argued that in the real world, the processing fluency basis of familiarity occurs primarily when the object or person is encountered in an unexpected context. In theory, meeting your spouse in your own kitchen should engender considerable processing fluency because of repeated exposures, leading to a strong familiarity response. However, this does not occur. In fact, such encounters curiously elicit no sense of familiarity. In contrast, if you unexpectedly spot your spouse sitting in the middle of your class as you lecture, this would arouse an intense and immediate sense of familiarity. Similarly, seeing your mail carrier at your front door arouses no sense of familiarity, but seeing him or her at the movie theater evokes a strong sense of familiarity due to the novel context (Reed, 1979). Applying this interpretation to deja vu, if an individual experiences a single familiar (but unrecognized) element in an unfamiliar context, the fluent reprocessing of this one element may elicit a deja vu experience specifically because the context is different.

Memory Explanations (Part 1)

An extensive literature documents that an individual’s response to a particular stimulus can be altered by a prior encounter in the absence of explicit (episodic) recollection of this previous experi-
ence (cf. Roediger & McDermott, 1993; Schacter, 1987). Speculation concerning implicit familiarity as a foundation for a deja vu was originally proposed more than a century ago by Osborn (1884), who suggested that individuals process a considerable amount of information without paying full conscious attention to it and that the subsequent reprocessing of this information may occasionally give rise to a sensation of subjective familiarity in the absence of recollection. What sets the deja vu experience apart from other implicit memory responses is an inordinately strong impression of familiarity in the absence of explicit recollection.

Not all models in this section provide a clear explanation of what causes this intense familiarity, but they do present reasonable frameworks within which the deja vu experience can be interpreted.

Conflict in source monitoring processes

According to the source monitoring framework (SMF; Johnson, Hashtroudi, & Lindsay, 1993; Mitchell & Johnson, 2000), as events are experienced, various features are encoded (perceptual, spatial, emotional, semantic details, temporal information, ongoing cognitive operations), depending on the processing that occurs. Remembering is a mental activity in which current mental experiences are attributed to past events on the basis of their qualitative characteristics and on the individual’s general knowledge and beliefs. Although deja vu has not been specifically interpreted within the SMF, it is relatively straightforward to do so. For example, suppose that you are excited about a first trip to Seattle, enter the airport terminal on your arrival, and have a strong deja vu experience. You know that you never have been in Seattle, but the terminal seems incredibly familiar.

According to the SMF, a deja vu experience could arise from the conflict in two types of source monitoring processes. That is, your attribution based on your general knowledge (of never having been in Seattle) is in conflict with the heuristic attribution that is most natural as based on qualities of the mental experience, which imply it is familiar from past perception. Such familiarity could arise from a number of different types of past events encoded in memory. Perhaps you have seen this airport setting in a movie, television documentary, or picture in a magazine, but your current mental experience does not include this additional information that would allow you to identify the source of the familiarity. If you had a sense of familiarity but could identify its source (e.g., a magazine article on the plane), you would not have a deja vu experience. If you could not identify the source of the familiarity but also thought it was likely that you might have been in Seattle before after all, you also might not have a deja vu experience.

Duplication of processing

Osborn (1884) suggested that it may not be the content of the memory that is duplicated in a deja vu but rather the particular cognitive processing that occurred on a prior occasion:

If at any time in our past lives we passed in actual experience or in imagination over a mental track, say a b c d e , and if to-day [sic] this track is again traversed, although the former experience itself may have been long forgotten, we have a sense that it has been through the mind before. . . . If the mind passes over only part of the former track, say b c d,we sometimes, in the dim recognition which arises, believe we have been over the whole before. (pp. 480–481)

This interpretation can account for why the strong familiarity essential to deja vu can occur in a completely novel setting.  Osborn’s position is similar to the theory of transfer appropriate processing (Kolers, 1973; Kolers & Roediger, 1984; Morris, Bransford, & Franks, 1977; Roediger, Weldon, & Challis, 1989), in which retrieval success depends on the correspondence between the way the information is processed during input and retrieval. If similar mental procedures occur on both occasions, then recollection probability is high. If the processes are dissimilar, the likelihood of remembering the information is low. Thus, if the processing of the new information duplicates the mental procedures that occurred with a prior but unrelated experience, an unexpected sense of familiarity and deja vu may result, even though the stimulus elements in both situations are different.

Neurological Explanations (Part 2)

Neural transmission delay

Another class of neurological interpretations assumes that the deja vu experience results from a momentary delay in neuronal transmission from the perceptual organ to the higher order processing centers of the brain. In one version, there is a slight increase in the normal time taken to transmit the message, due to a synaptic dysfunction, and this slight slowing in the routine processing time (several milliseconds) is misinterpreted as representing that the information is old (Grasset, 1904). Anjel (1896) noted that the fatigued state often accompanying deja vu may underlie this neural slowing, temporarily elongating the time between sensation and perception. The logic behind this position is vague and unspecified, and it seems at odds with research on perceptual fluency. More specifically, individuals interpret faster (easier) processing of information as indicating that the item has been experienced before (Jacoby, 1988; Jacoby et al., 1988). Thus, slower processing should imply that the information is new, not old.

Another version of this transmission delay interpretation involves two neuronal pathways rather than one and has more logical explanatory appeal than the single-pathway version. In the visual system, sensory information traverses multiple pathways between the sensory organ and the higher cortical centers (Goodale & Milner, 1992; Milner & Goodale, 1995; Schneider, 1969). In most instances, the information is first received cortically from the primary and then from the secondary pathway (Weizkrantz, 1986). When the normally brief difference in processing time between the two tracks becomes lengthened, the usually seamless integration of the two messages into a single perception becomes disrupted and is experienced as two separate messages (Comfort, 1977). The brain interprets the second version, through the slowed secondary track, as a separate perceptual experience, and thus the inappropriate feeling of oldness derives from the match with the first input processed moments earlier.

Another version of this dual-pathway speculation assumes that the primary perceptual pathway goes directly to the dominant hemisphere while the secondary pathway routes first through the nondominant and then to the dominant hemisphere (Ephron, 1963; Humphrey, 1923). When the delay of information from the nondominant to the dominant hemisphere is slightly extended, a deja vu results (Maudsley, 1889; Osborn, 1884; Weinand et al., 1994). A simpler version of this position is that the two hemispheres normally receive the same information simultaneously, but a slight delay of information to one hemisphere results in a déjà vu (Humphrey, 1923; Wigan, 1844). Weinand et al. (1994) and Ephron (1963) proposed that the preseizure electrical disturbance confined to one hemisphere may cause the slight temporal delay in the secondary pathway, resulting in deja vu. Ephron also speculated that a lesion in the nondominant hemisphere could occasionally slow information transmission from the nondominant to the dominant hemispheres, an interpretation he suggested could be tested during neurosurgical procedures through local anesthesia of the corpus callosum.

A final neurological interpretation of deja vu, also involving two perceptual pathways, assumes that the primary rather than the secondary pathway is delayed, causing the information from the secondary pathway to arrive slightly before that received from the primary pathway. Information from the primary pathway is routinely interpreted by the individual as the initial perception, so when this information arrives after the secondary pathway information it feels familiar because a “memory” match already exists, only milliseconds old (Comfort, 1977; Ephron, 1963).