Every time a child commits a mistake, the teacher punishes him for that mistake but still the teacher does not observe any change in his behaviour. Which policy is the teacher probably practicing on the student?

Negative reinforcement is a key concept in B.F. Skinner's theory of operant conditioning. Negative reinforcement involves strengthening a behavior through the removal of an aversive stimulus. People often confuse negative reinforcement with punishment, but the two are not the same. Remember, reinforcement is used to increase the likelihood that a behavior will reoccur, while punishment is used to decrease a behavior.