2. Watson and the behaviourists. By the 20th century, the idea of instrospection, as well as its scientific value and status was questioned by many. He suggested that introspection was subjective and varied greatly from person to person. Thus it is difficult to establish general principles of behaviour.
He also suggested that in order for psychology to be considered a science, it must be a focus on a measurable or an observable phenomenon, such as the Skinner box. Watson and Skinner focused on scientific processes and rigour in their experiments.