Edward Chase Tolman (1886–1959) was a devoted behaviorist who studied maze-running behavior in rats (a favorite topic of behaviorist researchers). Despite his expectations, he repeatedly observed behavior in rats that he could not explain solely by stimulus-response connections. He noticed that rats in a maze would often stop, look around, and check out one path, then another before choosing a particular route. He could only explain this behavior (and many other similar behaviors he observed) by inferring some kind of mental process. The rat seemed to have a mental picture of the layout of the maze and that directed its behavior. In this way, Tolman introduced the mind into the behaviorist stronghold. Even rats running mazes evidenced mental processes, some form of thinking about the problem.