The approach to psychology that focuses on the purpose of behavior is known as

Behaviorism

Explanation:

Behaviorism is a scientific approach. It focused on the objective and the scientific method of investigation of behavior. In this approach, it focused on the learning behavior of a person such as learning occurs through the interaction between the stimulus and the environment.

There was some basic assumption about the behavior in a manner:

It is assumed that all behavior of human beings or animals is learned through the association between environment and stimulus. Psychology is a science The behavior occurs through learning A little bit different in the way of learning behavior in human beings and animals. Behavior occurs association between stimulus and environment.