Bärbel Inhelder (1913-1997) was a Swiss developmental psychologist, the most famous co-worker of Jean Piaget. She was born in St. Gall, Switzerland and moved to Geneva in 1932 where she studied at the University of Geneva Institut Jean-Jacques Rousseau. She obtained her bachelor's (1935) and doctorate (1943) in psychology.
Inhelder worked at the University of Geneva until her retirement in 1983, collaborating with Jean Piaget in his experimental work on child development. Their collaboration began with her dissertation on children's conservation and continued for almost 50 years. Their many joint publications include The Growth of Logical Thinking from Childhood to Adolescence (1958), The Psychology of the Child (1966), and The Child's Conception of Space (1967).
Inhelder's work was particularly significant in the discovery of the stage of "formal operations" occurring in the transition between childhood and adolescence. This type of thinking involves deductive reasoning and the ability to reason hypothetically.
Barbel Inhelder died in 1997.