I do believe that we'll look at three of my favorite theories, which are also three of the most influential of the early theories of psychology: Behaviorism, Cognitive, and Humanistic theories.
Behaviorism as a theory is based on the idea that all behaviors are a direct result of conditioning, which occurs through interacting with the environment. Behaviorists study behaviors independent of internal factors such as mood, motivation, and personal preference. One advantage to this theory is that it allows behaviors to be studied and observed in concrete and definable terms. Behaviorism has given us the functional behavior assessment, which is one of the primary tools used to determine the causes of, and design modifications for, problem behaviors. According to this theory, all behaviors are the result of one of two processes. The first is called classical conditioning, and an example is the classic Pavlov's dog experiment. In classical conditioning, the initial stimulus is something that happens in the environment (i.e. the dog being fed), which results in a response behavior (i.e. the dog drools). Next, the initial stimulus is paired with another stimulus that occurs simultaneously with the first one (i.e. a bell rings while the dog is being fed). Eventually, the brain will associate the second stimulus with the original one automatically and respond accordingly (i.e. the dog drools when a bell rings). To give a less over-used and more human example, this theory would apply to a child who becomes very upset and cries every time the fire alarm goes off at school (original stimulus and natural response). Suppose that for some reason the school makes a habit of having a fire drill during times when the child is having a math test (the secondary stimulus). After repeated associations between math class and upsetting fire drills, the child may begin to experience anxiety and fearful behaviors during math tests even when a fire drill doesn't happen. Once the secondary stimulus is strongly associated with the response to the extent that the original stimulus can be removed entirely, this is now called a conditioned stimulus and a conditioned response. The ...