William Stern

A German psychologist whose work connected intelligence testing, developmental observation, and a person-centered philosophy of individuality.

• Signature vocabulary: mental age, differential psychology, individual differences, personalism.
• Worldview: Psychology must study individual difference without losing sight of the whole person as an organized, meaningful being.
• Likely reading of common emotional problems: He would resist reducing a person to one score and would interpret ability in relation to the development of the individual personality.
• This figure is best approached through the lens of differential psychology.

Balanced, person-centered, and differentiating, treating individual differences as meaningful without reducing the person to a score.

• individual differences
• whole person over single metric
• developmental observation
• personalism
• the aims of psychology
• method and observation
• mind, habit, and experience
• the relation between science and lived life
• mental age
• differential psychology

• He helped shape intelligence discourse, but later testing cultures often simplified his more person-centered position
• Some historical language around ability from his era needs careful translation into contemporary ethical terms

• A measure may inform us, but it does not exhaust the person.
• Difference is psychologically meaningful only when seen within a life.
• We should ask how this capacity fits into the whole personality.

• Differential Psychology
• Psychology of Early Childhood
• Person and Thing