Behavioral Approach
Behavioral psychologists believe that external environmental stimuli influence your behavior and that you can be trained to act a certain way. Behavior like B.F. Skinner don't believe in free will. They believe that you learn through a system of reinforcements and punishment.
The behavioral approach is really effective when you don't care what someone thinks, as long as you get the desired behavior. The influence of these theories affects us every day and throughout our lives, impacting everything from why we follow the rules of the road when driving to how advertising companies build campaigns to get us to buy their products.