This audio overview delves into déjà vu, which is the uncanny sensation of having already experienced something that is, in fact, new, even when you logically know it shouldn't be. While often a fleeting and harmless illusion, lasting only seconds, it can still feel profound or unsettling. This phenomenon is experienced by an estimated 60-80% of the population, and is particularly common among young adults between ages 15-25, suggesting a potential link to brain development or neural flexibility, and tends to decline with age.

Experts consider déjà vu a mystery, but leading theories suggest it primarily relates to memory and brain processing, involving memory errors, brain processing delays, and neurological misfires. Key explanations include split perception, where something is initially perceived with incomplete attention, and then fully observed, making it feel like two separate events, as the brain forms a memory even with limited initial information. Another theory points to minor brain circuit malfunctions, described as a "glitch" in the brain where present events are falsely perceived as memories due to a brief electrical malfunction, or delayed processing of sensory information transmitted along slightly different routes, which causes the brain to read a single event as two different experiences. Some experts suggest that short-term memories might even take a "shortcut" to long-term storage.

The Memory Recall or Mismatch Theory posits that déjà vu can occur when a new scene or event subconsciously resembles a past experience or a scene with a similar spatial layout (known as Gestalt familiarity) that the brain cannot consciously recall. This leads to a strong feeling of familiarity without the specific memory. Research by Anne Cleary, for instance, supports this, showing déjà vu is more likely when viewing scenes with structural similarities to forgotten past experiences, though people generally cannot accurately predict what will happen next, despite the strong conviction they often feel. The Dual-processing theory also suggests déjà vu happens when the brain's short-term and long-term memory pathways mistakenly activate simultaneously, causing the present moment to be misinterpreted as a memory.

While intriguing parallel universe hypotheses or past life memories exist as non-scientific explanations, suggesting a glimpse into alternate realities or reincarnation, there's no scientific evidence to support them; science attributes déjà vu to brain function.

Neurological links show that frequent or intense déjà vu can be a symptom of conditions like temporal lobe epilepsy, often occurring just before or during seizures, as a result of dysfunctional neuron activity. It may also be linked to anxiety, stress, or sleep deprivation, as high emotional states or exhaustion can cause the brain to process memories incorrectly. Some research also views déjà vu not as a mere malfunction, but as an adaptive memory quick-recognition strategy, suggesting it's a byproduct of a highly evolved mind's intricate memory and perception systems, prioritizing quick recognition over perfect accuracy, and serving as an error-detection mechanism. If déjà vu becomes a regular occurrence (more than once a month) or is accompanied by other symptoms like muscle twitching, sensory disruptions, or loss of muscle control, or if it is suspected to be a symptom of conditions like dementia, consulting a healthcare provider is recommended.