B.F. skinner

Meaning: Skinner was a behaviorist who studied how consequences control voluntary behavior, using the operant chamber ("Skinner box") with rats and pigeons. Behavior followed by a reinforcer becomes more likely. Behavior followed by punishment becomes less likely. He focused on observable behavior, not on internal mental states.

Positive means a stimulus is added. Negative means a stimulus is removed. Reinforcement raises the behavior's frequency and punishment lowers it. This gives four cases: positive reinforcement (add a reward), negative reinforcement (remove an aversive stimulus), positive punishment (add an aversive stimulus), and negative punishment (remove a pleasant stimulus).

Reinforcement schedules: fixed-ratio, variable-ratio, fixed-interval and variable-interval. Variable-ratio gives a high, steady response rate that resists extinction. Fixed-interval gives a scalloped pattern. Shaping reinforces successive approximations of a target behavior.

On the MCAT: A passage describes an animal or person and a consequence. You classify the case, predict whether the behavior will increase or decrease, or compare schedules by response rate and resistance to extinction.

Common confusion: Negative reinforcement is not punishment. It still increases behavior, because removing something unpleasant (such as an alarm that stops when you buckle your seatbelt) rewards the action. Also keep operant conditioning (voluntary behavior and consequences) separate from Pavlov's classical conditioning (paired stimuli and reflexive responses).