Read More: Popular Science
Serial killer David Berkowitz, also known as the “Son of Sam,” famously claimed that he heard voices in the form of a dog telling him to commit murder. But hearing voices isn’t necessarily a sign of psychosis. In fact, according to the authors of a recent study published in the journal Brain, enhanced attention-related nerual pathways might cause these illusory sounds. People hear them because their brains may be especially primed to pick up speech. “It's true that lots of people who hear voices have serious mental health issues,” Ben Alderson-Day, a psychological research at Durham University and lead author on the study told Popular Science. “But roughly 5 to 15 percent of the general population will have some experience of hearing unusual voices at some point in their lives. We think potentially up to one percent might have pretty frequent experiences and just don’t really tell anyone and get on with their everyday lives.” It’s this one percent that catches psychologists' attention. Because this group isn’t clinically psychotic and thus typically not on psychotropic medication, researchers can study their tendency to hear voices without the confounding factors of mental illness. They think these benign voices hearers could bring some explanation to why humans hear voices, and perhaps a more broad understanding of the brain. “There’s an increasingly popular theory on how our brain makes sense of the world. Rather than just receiving sensory information passively, our brain is actively making predictions about the world and looking for meaningful patterns,” says Alderson-Day. The theory called predictive processing or predictive coding posits that a lot of our experience of the outside world is more about what we expect we happen rather than what is actually happening. It may explain, for example, why we tend to see shapes in clouds and Rorschach blots. We experience what we expect to experience, and we only change those predictions or expectations once we have enough evidence forcing our hand.