We’ve all been there. “I swear we’ve had this conversation before,” is a line I’ve uttered on many occasions, sometimes when I’ve genuinely thought as much, at other times when I’ve just been desperate to change the subject.
Déjà vu has long been a source of mystery, and there are countless theories for why it happens, some more far-fetched than others. However, Akira O’Connor from the University of St Andrew’s reckons he’s solved it once and for all, and believes that déjà vu is actually a sign of our brains checking through memories.
O’Connor and his colleagues set up an experiment designed to trigger false memories and ultimately the sensation of déjà vu in a group of human guinea pigs. They read a number of related words -- in the example detailed over at New Scientist: bed, pillow, night, dream -- to the volunteers, but didn’t mention the one linking them all together. In this case, sleep.
The researchers then asked if they’d mentioned any word beginning with the letter ‘s’, to which the people shook their heads. When quizzed on the words later, however, the people in the group felt familiar with the word ‘sleep’, despite knowing that they couldn’t have heard it.
According to O’Connor, they reported feelings of déjà vu.
The results of fMRI scansshowed that the areas of the brain typically involved in decision-making became active during the experiment, as opposed to the areas associated with memories. O’Connor therefore believes that déjà vu occurs when the brain scans itself for memory errors.
If the findings are confirmed, it's still unclear if déjà vu is a sign of having a healthy or unhealthy loaf. On the one hand, it could mean that your memory checking system is working well and that you’re less likely to misremember events, but on the other, not experiencing déjà vu may be a sign of having a flawless memory system. [New Scientist]