I apologize if this is a repost, but I think that it’s worth seeing again. Biologist and science educator Joe Hanson presents scientific explanations for why we sometimes think that we’re doing the same thing over and over again.
One hypothesis goes like this: our brains continuously scan inputs from our senses. When the brain determines that something is familiar, it notes that familiarity. The hippocampus responds by recalling the memory attached to that sensory input. Sometimes the steps in this process may get out of order. When that happens, the brain may determine that something is familiar, but the hippocampus can’t find an associated memory. This induces déjà vu.