Unlike normal animals or those with sham lesions, rats with hippocampal and septal lesions behaved in an operant chamber as if a dependency existed between pellet delivery and their behavior, despite the fact that reinforcement was based on time, not behavior, and was therefore free. This superstitious behavior did not result from a general inability to inhibit responding, as responding rapidly ceased when the pellets were discontinued. These findings suggest that the hippocampus integrates information regarding response-reinforcer relations, which in the normal rat permits superfluous operant behavior to be eliminated.