[A] While working as a research fellow at Harvard, B. F. Skinner carried out a series of experiments on rats, using an invention that later became known as a “Skinner box.” A rat was placed in one of these boxes, which had a special bar fitted on the inside. Every time the rat pressed this bar, it was presented with food. The rate of bar-pressing was automatically recorded. Initially, the rat might press the bar accidentally, or simply out of curiosity, and as a consequence receive some food. Over time, the rat learned that food appeared whenever the bar was pressed, and began to press it purposefully in order to be fed. [B] In behavioral psychology, there are two major forms of learning: classical conditioning and operant conditioning. Classical conditioning was first demonstrated by Ivan Pavlov in the 1890s. In his experiments, Pavlov rang a bell while presenting food to dogs. Naturally, the dogs salivated at the sight and smell of food, which are called the unconditioned stimulus and unconditioned response, respectively. Over time, the dogs began to associate the neutral sound of the bell with food. Eventually, the bell alone caused them to salivate. In this case, the bell became a conditioned stimulus, and the salivation became a conditioned response. This process showed that behavior can change through the pairing of stimuli. Operant conditioning, on the other hand, focuses on how consequences influence voluntary behavior. One of the elements used in this conditioning is reinforcement. Reinforcers increase the likelihood of a behavior being repeated. These can be positive (adding a stimulus) or negative (removing a stimulus). For example, receiving dessert for eating vegetables is positive reinforcement, while getting out of homework for doing well on a test is negative reinforcement.
