Thoughts on Déjà Vu
Below I offer a brief interpretation of the déjà vu experience based on current scientific evidence. I first provide my opinion as to why déjà vu occurs and then offer an argument as to why other interpretations may lack explanatory power.
The most appealing explanation of the déjà vu experience is the account of delayed neural transmission between low-level and high-level cognitive processes. In this essay, I’ll take the stance that déjà vu occurs because a disruption in neural processing gives rise to a sense of perceptual familiarity for an event that has no correspondence in memory. In other words, déjà vu is the result of anything (be it micro-seizures in the temporal lobe or a lack of attention or energy during visual processing) that causes an event to seem familiar to low-level perceptual processes but unfamiliar to high-level memorial processes. Although a distinction between perception and memory may prove unrealistic, I hope that it will at least not prove unreasonable.
Establishing déjà vu as a phenomenon based in perception rather than in memory will help to distinguish ‘familiarity’ as it occurs in the perceptual system from ‘familiarity’ as it occurs in the memory system. In perception, familiarity can occur when two pathways that generally operate in unison become uncoordinated, as when sensory information from the secondary visual pathway is processed after information from the primary visual pathway (Brown, 2003). This inconsistency leads the perceptual system to interpret the information coming from the slower pathway as already having been processed, and thus perceptually familiar. Given the speed with which neural processing occurs, it is reasonable to suspect that by the time this inconsistency has been detected, the memory system has not had the chance to process, and thus recognize the event as old. This may be why déjà vu is often reported containing elements of familiarity but not elements of recollection. More importantly, this could explain why the sense of familiarity experienced in déjà vu feels fundamentally different than the sense of familiarity experienced in other contexts (e.g., such as when recognizing an old friend on the bus). In the latter, the memory system unconsciously recognizes a new instantiation of a percept as similar to an old instantiation of a percept and dishes up a feeling of familiarity (noticing how the current instantiation is recollective of the past). In the former, however, the perceptual system recognizes a new instantiation as the same as an old instantiation and dishes up a feeling of déjà vu (with the memory system unable to provide a recollective element for that event). That this phenomenon is perceptual in nature explains why people often report a heightened sense of awareness for the present while experiencing déjà vu: the perceptual system is forced to orient the mind to the present rather than to the memory system, which would otherwise be issuing feelings of familiarity with recollective properties from the past.
For these reasons, I find it difficult to consider déjà vu as relating to fluency or other more common feelings of familiarity. That none of these feelings occur as infrequently or with such eerie intensity as déjà vu, leads me to suspect that they are derived from different mechanisms. Moreover, it seems particularly unlikely that source monitoring errors form the basis of déjà vu. Perhaps this is drawing too strongly from personal experience, but while recognizing a person or object out of context may lead me to process an event less fluently, it surely does not lead me to interpret the event as if I were experiencing a glitch in the Matrix.
In conclusion, any similarities between feelings of familiarity and déjà vu likely arise, not because both are products of memory, but because both are products of cognition.
References
Brown, A. S. (2003). A review of the deja vu experience. Psychological bulletin, 129(3), 394.