- The researchers looked at MRI brain scans of a large group of healthy adults. In particular, they were looking for the paracingulate sulcus (PCS), a fold near the front of the brain. There’s a lot of variability in the PCS: some people have quite distinctive folds, others have barely any. It’s in a part of the brain known to be important in keeping track of reality, which is why the researchers chose to study it. Of the 53 people selected for the study, some had this fold on both sides of their brain, some had it on one side, and some had no fold.
- The participants saw some full well-known word pairs (“Jekyll and Hyde”) and some half pairs (“Jekyll and ?”). If they only saw half of a pair, they were asked to imagine the other half (“Hyde”). After each pair or half pair, either the participant or the experimenter said the whole pair aloud.
- Once they’d seen all the pairs, the participants were asked two questions about each phrase: Did you see both words of the pair, or just one? And who said the phrase aloud, you or the experimenter?
- People who didn’t have the fold on either side of their brains did worse on both questions—remembering if something was real or imagined, and remembering who’d done something—than people whose brains had the fold. But they felt as confident in their answers, meaning they didn’t realize they’d been mixing up internal and external events.
Along with schizophrenia, the PCS would also be a place of interest for study on the ability to lucid dream.