Behavioristic psychologies can be referred to as behaviorism, behaviorist theory, or behavioral psychology. All these synonyms indicate the same study of behavior in humans and animals, with a primary focus on observable actions and their environmental determinants. Another term commonly used is the 'stimulus-response theory' that emphasizes the cause-and-effect relationship between observable stimuli and behavioral responses. Some researchers also use the term 'operant conditioning' to describe the learning of new behaviors based on environmental consequences, rewards, and punishments. However, despite the use of different terms, all these synonyms represent the same approach to psychology that emerged in the early 20th century, challenging the introspective and unobservable concepts of earlier schools of thought.