You hear a new song on the radio, and the next day you're humming the tune—without ever having tried to team it. Such "implicit learning" goes on all the time, says Gregory Berns, M.D., Ph.D., and in some cases, it's the best way to master new knowledge.
Berns, a senior resident in psychiatry at the University of Pittsburgh Medical Center, designed an experiment in which subjects pressed a button every time a light flashed. Unknown to them, the flashes followed a pattern, and in the middle of the session the pattern changed. Berns and his colleagues found that reaction times went down as participants learned to anticipate the flashes, then rose again when they were confronted with an unfamiliar sequence. The subjects themselves remained unaware that the flashes had followed any order.
Brain scans revealed that the right ventral striatum, deep in the brain stem, and the right cerebral cortex, located over the right eyebrow, were involved in the task. "As the prefrontal cortex is learning to predict what's coming next, the striatum is monitoring how well the predictions are holding up," says Berns.