More than a decade ago, scientists established a link between schizophrenia and the rare ability to tickle oneself. Now researchers in France have expanded on the findings, reporting in the journal Consciousness and Cognition that the behavior can be found not just in those with full-blown schizophrenia but in otherwise healthy people who score high on tests that look for schizophrenic-like traits. Examples of the latter might include a vivid imagination or mild paranoia, explains the the British Psychological Society's Research Digest. After studying 397 healthy students, 27 of whom scored highly on the Schizotypal Personality questionnaire and 27 students of whom scored very low, researchers observed all students being tickled by someone else with a feather and trying to tickle themselves with a feather. Those with the high scores weren't more ticklish in general, but they were more vulnerable to self-tickling.
The results don't mean such people are doomed to develop schizophrenia, but "they are consistent with the idea that the same brain processes (involved in movement control and monitoring) that may contribute to the symptoms experienced by patients with schizophrenia, may also contribute to schizophrenia-like beliefs and experiences in healthy people," says BPS. It turns out that fMRI scans have revealed most of us can't get away with tickling ourselves because our brains can predict what the sensation will be, and thus we are not fooled, reports Medical Daily. This is good; we're better able to distinguish between external threats such as an incoming jaguar's jaw and internal ones we have invented. That the ability to self-tickle is linked to, for instance, a higher rate of feeling controlled by outward forces may help psychologists better understand the brain mechanisms at play in a schizophrenic hallucination. (Scientists may have found the disease's genetic trigger.)