"The problem with Freud is that he didn't have any data."

"A person who has been punished is not thereby simply less inclined to behave in a given way; at best, he learns how to avoid punishment."

"We shouldn't think about what people feel, but about what they do."

"Freedom is a matter of contingencies of reinforcement, not of some inner state of mind."

"The ultimate aim of the science of behavior is to understand and explain human behavior."