What is "Deja Vu"?
Soumya Nakka '26
Déjà vu, French for “already seen,” occurs when a person feels like they have already experienced a novel situation. This momentary feeling, invoking a sense of familiarity, confusion, and misrecollection, is caused by memory processes in the brain. There are several forms of déjà vu, but it can be primarily categorized into two types: non-clinical and pathological. Non-clinical déjà vu is common in young adults and approximately 60-85% of all healthy individuals (Deja vu, ScienceDirect Topics). Additionally, recent advancements, such as a study on psychology conducted by Andrew Hubert of the University of Southern Mississippi, Sarah Myers of Minnesota State University, and Anne Cleary of Colorado State University uncovered new evidence pointing to déjà vu triggering a feeling of prediction (FOP), where an individual’s mind registers an illusory ability to foresee the future. The team’s work also connects broadly to any type of familiarity detection, not just false memory but also accurate recognition of frequent stimuli in one’s environment. This extends the boundaries of FOP outside the neural mechanisms of déjà vu (Huebert et al., 2025).
Déjà vu arises from continuous signals and interactions between key components of the medial temporal lobe. Whereas the abilities to form memories and process information are linked to the hippocampus and the parahippocampal cortex, the familiarity largely associated with déjà vu is directed by the perirhinal cortex. This region of the brain encodes and retrieves information to sort objects in a categorical fashion, giving individuals an understanding of what is familiar versus unfamiliar (Deja vu, ScienceDirect Topics).
Research on electrical simulation has informed psychologists that activating the prehinal and entorhinal cortices is the easiest method to trigger déjà vu (Bartolomei et al., 2004). However, the hippocampus is still needed for complete stimulation. As a result of abnormal or enhanced theta-phase synchronization between the rhinal cortex and the hippocampus, the brain may accidentally register a novel experience as a coherent, formerly encoded memory. Theta-phase synchronization, or the “glue that binds human associative memory,” is a type of coordinated timing mechanism at theta frequency that allows distant regions of the brain to combine different sensory details into one condensed memory (Clouter et al., 2017).
Additional studies on the temporoparietal junction, the area in the brain where the temporal and parietal lobes intersect, display that the region is vaguely connected to other interferences with the body. An example of such interference would be temporal lobe epilepsy, where déjà vu is listed as a possible symptom for patients. The pathological form of déjà vu in epilepsy tends to last longer and is accompanied with other hallucinations or negative feelings, making it distinctly different from non-clinical déjà vu (Deja vu, ScienceDirect Topics). Some of these feelings include “depersonalization, fear, or the presence of vivid memories or olfactory hallucinations.” (Cleary et al., 2021).
An important point recognized in previous studies, which guided the evidence collected by Huebert, Myers, and Cleary, is that not every instance of déjà vu is accompanied by FOP. By recognizing this distinction, it can be asserted that déjà vu is not simply a feeling of what is about to happen in a situation. Rather, an individual’s FOP is influenced by situations with high familiarity and intensity, and a common instance of this is during déjà vu.
In their first experiment, the three researchers used modified virtual reality to induce a feeling of familiarity and did not inquire whether the participants felt déjà vu to prevent bias (Huebert et al., 2025). This virtual tour method included exposing participants to various scenes, including commonly visited areas such as public complexes, apartments, and homes, and then displaying completely new scenes that have either the same or a different layout of appliances, furniture, and other objects (Cleary et al., 2021). To further increase familiarity in the experiment, the similar arrangements were shown more than once. Participants were then prompted to answer three questions regarding the similarity of the studied layouts to the new scene, the level of familiarity of the space, and the predicted direction of the video turn (left or right) (Huebert et al., 2025).
While analyzing their results, the researchers found unusually high predictive accuracy. The scholars suspected that prompting participants to recount the original source memory in the first question inadvertently enabled participants to retrieve the correct memory and apply it to the last question, the turn prediction. To account for this, the team conducted a follow up trial with conditions identical to the first with the exception of prompt order (Huebert et al., 2025). Thus, the question about source memory was moved to the end and level of familiarity was isolated as the primary variable affecting a participant’s perception. Consequently, the rates of predictive accuracy dropped, undermining the notion that familiarity could provide predictive ability outside intuition when the source memory has been forgotten (Huebert et al., 2025).
For the third and final experiment, half of the participants were asked to answer questions about familiarity and FOP, while the other half were only asked about sensing a FOP. The results for both groups showed similar patterns, so the researchers discerned that FOP is automatically guided by a detection of familiarity, regardless of whether participants are consciously thinking about the idea of familiarity (Huebert et al., 2025). The team also found a strong link between memory traces and illusory feelings, implying that higher altered chemical and physical changes to the brain from experience lead to surges in déjà vu. After noting that participants who were asked about familiarity first in experiment three had lower rates of FOP, the team looks forward to evaluating the impact of time and fading memory on FOP in the future. Additionally, there is room left to investigate the effects of non-spatial aspects of memory, such as sounds and people, on FOP and déjà vu.
Though it is a very common occurrence, déjà vu is still not fully understood; often, the patterns observed in this sensation conflict with each other. Typically, errors in memory are correlated with decline of brain function and age-related forgetfulness. Yet, déjà vu, a phenomenon connected to the distortion and misrecollection of memory, peaks in young adulthood and decreases with age. Ultimately, déjà vu cannot “fit into a neat category of typical memory function” (Deja vu, ScienceDirect Topics). However, through continual advancements and precise research, like the profound FOP conclusions produced by Hubert, Myers, and Cleary, scientists will continue to transform correlational data into information backed by experimental evidence, fortifying hypotheses in older studies and clarifying our understanding of the human mind.
References
Bartolomei, F., Barbeau, E., Gavaret, M., Guye, M., McGonigal, A., Regis, J., & Chauvel, P. (2004). Cortical stimulation study of the role of rhinal cortex in déjà vu and reminiscence of memories. Neurology, 63(5), 858–864.
https://doi.org/10.1212/01.wnl.0000137037.56916.3f
Cleary, A. M., Neisser, J., McMahan, T., Parsons, T. D., Alwaki, A., Okada, N., Vosoughi, A., Kheder, A., Drane, D. L., & Pedersen, N. P. (2021). Subjective distinguishability of seizure and non-seizure déjà Vu: A case report, brief literature review, and research prospects. Epilepsy & Behavior, 125. https://doi.org/10.1016/j.yebeh.2021.108373
Clouter A, Shapiro KL, Hanslmayr S. Theta Phase Synchronization Is the Glue that Binds Human Associative Memory. Curr Biol. 2017 Oct 23;27(20):3143-3148.e6. doi: 10.1016/j.cub.2017.09.001. Epub 2017 Oct 5. PMID: 28988860.
Deja Vu - an overview, ScienceDirect Topics. www.sciencedirect.com. https://www.sciencedirect.com/topics/neuroscience/déjà-vu
Huebert, A. M., Myers, S. J., & Cleary, A. M. (2025). Experimental evidence that illusory feelings of prediction can be caused by familiarity detection. Consciousness and Cognition, 133, 103904–103904. https://doi.org/10.1016/j.concog.2025.103904