1. Personalistic psychology. Stern defined a psychology as “the science of the person as having experience or as capable of having experience”.
1.1. He considered a person as the primordial unity and central category, as a unique, living and genuine whole, striving toward goals, self-contained, inner-determined and open to the world.
1.2. Stern introduced the concept of “the personal world” (gelebte Welte) (1935) in which the individual really exists, that is different from “expierence wold” and “objective world”.
He stated that the personal development is no mechanical interchange between the person and his environment, but it involves a readiness to realize values which are suggested by environment.
When considering the sphere of motivation, Stern dealt with will, which implies conscious anticipation of end and stated that spontaneous striving toward enhanced status and power activates the intellect more than does mere self-preservation.
1.3. Stern pays great attention to the interaction of the individual and the surrounding world. He introduced “theory of convergence” suggested that personality is formed by interaction between maturation and social environment and terms- introception - the transformation of foreign targets in their own individual goals and convergation
2. Differential psychology. With his book “Differential psychology” (1900) Stern founded of the same name discipline. In this work he attempted to classify people according to types, norms, and aberrations.
3. Concept of the intelligence quotient. He introduced to intelligence testing and invented the concept of the intelligence quotient, or IQ (1912). He initiated the use of tests for vocational guidance and for the selection of gifted children.
4. Child and educational psychology.
Stern is best known for his contributions to child psychology, especially for his studies of the development of language in children (thus he said that the child (about one and a half years) makes one significant discovery – that each thing has its name, and each word has its meaning).
Sterns Since 7 April 1900, when Stern and his wife Clara welcomed their first child, they recorded observations on the psychological development of their own children. Later they published two monographs based on diaries: Erinnerung, Aussage, Lüge in der ersten Kindheit (1905) and Die Kindersprache (1907).
Game theory. He first identified the content and form of child's play, and considered the game as a necessary condition for the personal development of the child.
Development Stern understood as growth, differentiation and transformation of mental structures.
5. Legal (forensic) psychology.
Stern is known for his investigations of the psychology of testimony and deposition and courtroom procedure. He stated that recall memories are generally inaccurate and depended on time.
Stern's philosophy, was expressed as a form of personalism. In his conception he tried to synthesize the of mind and body,
vital forces and impersonal science, causality and teleology, associationism and holism. He stated that the person is to be distinguished from the thing. The person is a whole, individuality endowed with purposive, self-originating activity, while the thing is an aggregate and quantity.
In 1906 Stern founded the Institute for Applied Psychology (In collaboration with Otto Lipmann). In 1908 he established the Journal of applied psychology of which he remained coeditor until he left Germany in 1933.
He received his PhD in psychology from the University of Berlin in 1893. (Doctoral dissertation “Analogy in popular thought”.
He taught at the University of Breslau (1897-1916), at the University of Hamburg, Professor of Psychology (1916-1933), where he also remained until 1933 as Director of the Psychologic Institute.
In 1933, fleeing from the Nazi regime, he emigrated first to the Netherlands, then to the United States where he taught as Lecturer and Professor at the Duke University (1933-1938).
In 1931 he was elected President of the German Psychological Society.
W. Stern was married to Clara Joseephy, a psychologist. They had 3 children: Hilde, Eva and Günther, who became an German writer and philosopher.