Researchers found that a monkey's state of attentiveness may be encoded in the shapes and speeds of slow electrical waves that course over the surface of the brain. Like a surfer that avoids smooth water and favors more active waves, the brain uses faster, choppier waves to process information to which it is paying attention. By separating how the brain encodes its state of attention versus stimuli to which it is responding, scientists hope to understand sleep, anesthesia, attention, and disease better.