Behavior modification is the systematic application of learning principles and techniques to assess and improve covert and overt behaviors. It is based on classical and operant conditioning. There are several stages including identifying the target behavior, developing a new behavior to replace it, strengthening the new behavior, and maintaining it over time. Common techniques include positive and negative reinforcement, punishment, modeling, shaping successive approximations, and systematic desensitization. The goal is to help individuals develop desirable behaviors and reduce undesirable ones to better function in society.