Vsauce Michael discusses the phenomenon of deja vu, its occurrence, and why it's difficult to scientifically study. He explains that humans don't seem to experience deja vu until they're at least eight or nine years old, and it's most frequent in teenagers and young adults, tapering off as people age. This might be related to brain development.
Deja vu may be a symptom caused by many possible factors. One popular theory involves a disconnect occurring between the deep structures of the brain that process our experiences unconsciously and the parts of the brain that are conscious of what we experience and process it, then tell us what we're seeing.
The brain processes the visual information in multiple stages. For example, the visual cortex isn't the first stop that information makes instead it stops and lots of other places for instance the amygdala where it may be processed at an involuntary emotional level and the tectum which is involved in preliminary visual processing and helps control eye movements.
This disconnect may be the cause of deja vu. For example, if one experienced event A and then B and then C, and the inner parts of the brain committed to memory and generated an emotional response but then a fraction of a second later, the visual cortex finally gets around to telling the conscious aware part of the brain what it's seeing, it might say "we've already done that, we're looking at A and then B and then C", leading to the feeling of deja vu.
Deja vu is not the only phenomenon that can cause confusion. There's also something known as "press que vous" or tip of the tongue, where you know you know something but for the life of you at that moment you cannot call it. This could be because other words similar to the target word are being remembered and your brain is actively blocking other stuff around it, including the word you're actually looking for.
In conclusion, the feeling of familiarity for what we do know can't always be trusted.
1. "Deja vu" is a phenomenon where the current situation feels like it's happened before, but you don't know when or how it became so familiar.
2. Scientifically studying deja vu is challenging because there's no reliable way to cause it to happen in people's heads in a laboratory.
3. Humans don't seem to experience deja vu until they're at least eight or nine years old. It's most frequent in your teens and 20s and then tapers off as you get older.
4. Deja vu may be a symptom with many possible causes. Popular theories involve a disconnect between the deep structures of the brain that process our experiences unconsciously and the parts of the brain that are conscious of what we experience.
5. The visual system in the brain processes images and becomes aware of what we're seeing. The visual cortex isn't the first stop that information makes. It stops and lots of other places for instance the amygdala where it may be processed at an involuntary emotional level.
6. People with blindness caused by brain damage to the visual cortex cannot see anything they don't report seeing or recognizing, however, the other preliminary parts of the brain that get that message are still healthy. Despite being legally blind, these people exhibit what is known as blind sight.
7. The brain processes visual information in a series of steps, and if these steps are temporarily out of sync, it could lead to deja vu.
8. Minor epileptic events are quite common and are similar to the phenomenon known as a hypnagogic jerk.
9. Patients who experience chronic and persistent deja vu tend to have brain damage in the temporal lobes of their brain.
10. Deja vu is not the only phenomenon that can occur. There's also "press que vous" or tip of the tongue, which happens when you're familiar with something, you know you know it, but for the life of you at that moment you cannot call it.
11. The "press que vous" effect suggests that your brain is actively blocking other stuff around it, including the word you're actually looking for.
12. "Jame vu" is when something that you know, something that you're familiar with all of a sudden seems brand new and bizarre. Schizophrenic patients will sometimes see people they know and insist that it's not the person they know instead it's an imposter.
13. The feeling of familiarity for what we do know can't always be trusted.