Watson adopts the experimental methods and observation methods commonly used in natural science, and the object of psychological research is not consciousness but behavior. Hall accepted this theory of evolution and complex speech and applied it to the theory of individual psychological development.

Behaviorism holds that psychology should not study consciousness, but only behavior. The so-called behavior is the combination of various physical reactions that organisms use to adapt to environmental changes. These reactions are nothing more than muscle contraction and gland secretion. Some are expressed in vitro, while others are hidden in vivo, with different intensities.

Stanley Hall glanville Stanley Hall1844.02.01-1924.04.24, American psychologist and educator, the first doctor of psychology in the United States, the founder of the American Psychological Association and the first American disciple of Feng Te.