When we humans make a mistake, we have an instinctive “oops” reaction in our brains: a spike of negative voltage in the medial-front cortex. While this is something that has been observed by scientists, the reason why was a little more unclear.

To examine what effect this mistake response has on our behavior, two psychologists from Vanderbilt University in Nashville, Tennessee — Ph.D. candidate Robert Reinhart and assistant professor of psychology Geoffrey Woodman — designed a cap that administers a low-level current to the brain to simulate the spike. They hypothesized that the spike plays a role in learning, allowing the brain to learn from mistakes.

“That’s what we set out to test: what is the actual function of these brainwaves?” Reinhart said. “We wanted to reach into your brain and causally control your inner critic.”

The cap secured two saline-soaked sponges to the test subject’s head, one to the cheek and one to the crown. Through these sponges, the researchers applied 20 minutes of transcranial direct current stimulation (tCDS) — one of the safest ways to non-invasively stimulate the brain.

They applied three types: anodal (from the crown to the cheek); cathodal (from the cheek to the crown); and control, which replicated […]