Psychology is the study of the behavior of living organisms. People who study behavior are called psychologists. Many studies have been done by these people to try to understand why humans or animals do what they do. The four main goals of psychology are to describe what happened, explain why it happened, predict what event is likely to happen next, and change to avoid undesirable consequences. Psychologists study the process of thinking, learning, cognition, emotions, motivations and personalities. An example of a study that has been done would be why a dog salivates at the sound of a bell and a show. This behavior is because a conditioned stimulus becomes a conditioned response. Another experiment done was done with a baby and a white mouse to see if the baby would be scared if something happened while catching the mouse. There are several types of psychologists for different problems. An example is a school psychologist. In education and school psychology, they study the education process and work to promote the intellectual, social and emotional development of children in school settings. The main type of psychology is called clinical psychology, specializing in the assessment, diagnosis, and treatment of mental and behavioral disorders. Behavior is any observable action or reaction of living organisms. There are many levels of behavior studied in psychology. Some psychologists focus on behaviors that, at a high level, resemble aggression or prejudice. There are four main characteristics necessary for a behavior to be observable: the organism itself, motivation, knowledge, and skill. Behavior cannot be studied without the organism present in the body. Also, motivation must be in place for the study of behavior because it is an immediate cause of a behavior. Knowledge is something that the organism already knows. To examine it you need to understand the environment and what it knows, thinks and remembers..