Building on Edward Thorndike’s earlier Law of Effect, Skinner elaborated the way animals and humans learn from rewards and punishments. If a behavior is followed by a reward, it is likely to be repeated. If it is followed by a punishment, it is less likely to be repeated. Through research on rats and other animals, Skinner explored in great detail how the timing, frequency, and predictability of rewards and punishments affect behavioral change. These basic concepts of operant conditioning were viewed as the foundation of all learned behavior in both humans and animals. While we now know that there are many complex forms of thought that operant conditioning cannot explain, these principles do tell us a tremendous amount about basic forms of learning and memory.