Introduction

The term "deja vu" comes from the French for "already seen." It refers to the unsettling sensation that a new situation is familiar. While fleeting, the feeling can be quite vivid, leading some to believe they genuinely have had the experience before. Surveys indicate 60-100% of healthy individuals report having experienced deja vu (Brown, 2003). While common and generally harmless, deja vu remains a poorly understood phenomenon. This paper will review the current scientific literature on deja vu, including proposed explanations, prevalence, associated factors, and implications for cognitive functioning.

Proposed Explanations

Several theories have been put forward to explain deja vu, but no single account has emerged as definitive. One proposal is that deja vu results from divided attention (Brown, 2003). Familiarity results when one pays attention to a scene as a whole, whereas paying attention to details feels novel. Deja vu may occur when attention shifts between these processing modes, resulting in the feeling a novel scene is familiar.

Fatigue and anxiety are other oft-cited factors. Fatigue may disrupt memory formation, causing new events to feel familiar (O'Connor & Moulin, 2013). Anxiety is proposed to create a sense of recognition for threatening situations as a defense mechanism (Sno et al., 1994).

Abnormalities in memory retrieval and formation are a neurocognitive explanation. Some propose misfiring neurons cause memories to be improperly encoded, creating false familiarity (O'Connor & Moulin, 2008). Others suggest short-term memories are mistaken for older memories (Brown, 2003).

Prevalence

Estimates suggest 60-100% of healthy adults have experienced deja vu (Brown, 2003). Frequency decreases in older age, with one study finding 89% of people under 25 reported deja vu compared to 36% over 50 (Sno et al., 1994). Intensity and duration vary substantially between individuals. While many describe mild feelings of familiarity, some experience deja vu intensely or for extended periods.

Associated Factors

Deja vu has been linked to medical conditions like temporal lobe epilepsy, anxiety disorders, and schizophrenia (Illman et al., 2012). Those with epilepsy frequently experience prolonged episodes during seizures. Studies indicate patients with dementia, PTSD, depression, and schizophrenia also report elevated rates of deja vu. Travel fatigue, sleep deprivation, and recreational drugs are additional associated factors (Brown, 2003). While correlation exists, how these conditions interact with deja vu remains unclear.

Implications

The benign nature of most deja vu means limited research exists on implications. However, some propose frequent or intense experiences could indicate neurological dysfunction (Illman et al., 2012). For example, temporal lobe epilepsy patients often experience deja vu at seizure onset. In healthy individuals, pronounced deja vu may signify abnormalities in memory pathways. More research is needed to elucidate if deja vu frequency varies in clinical populations. Investigation of neural correlates could also clarify if deja vu results from specific neurological disruptions.

Conclusion

In summary, deja vu is a common but poorly understood experience. Leading explanations propose divided attention, anxiety, fatigue, or disruptions in memory formation underlie the sense of false familiarity. While typically transient and benign, studies link elevated rates of deja vu to conditions like epilepsy and schizophrenia. Further research on prevalence across populations and neural correlates is needed to elucidate the mechanisms of this strange phenomenon. A greater understanding of deja vu may provide insight into the intricacies of memory encoding and retrieval in the brain.

References

 Brown, A.S. (2003). A review of the deja vu experience. Psychological Bulletin, 129(3), 394-413.

 Illman, N.A., Butler, C.R., Souchay, C., & Moulin, C.J. (2012). Deja experiences in temporal lobe epilepsy. Epilepsy Research and Treatment, 2012.

 O'Connor, A.R. & Moulin, C.J. (2008). Normal patterns of deja experience in a healthy, blind male: challenging optical pathway delay theory. Brain and Cognition, 68(2), 156-9.

 O'Connor, A.R. & Moulin, C.J. (2013). Deja vu experiences in healthy subjects are unrelated to laboratory tests of recollection and familiarity for word stimuli. Frontiers in Psychology, 4.

 Sno, H.N., Draaisma, D., & Linszen, D.H. (1994). The deja vu experience: Remembrance of things past? American Journal of Psychiatry, 151(11), 1587-1595.