Arnold (Lucius) Gesell

Psychologist, born in Alma, Wisconsin, USA, the brother of Gerhard Gesell. He studied at Clark and Yale universities, became Director of the Clinic of Child Development at Yale in 1911, and also taught at Yale School of Medicine (1915–48). He later acted as research consultant to the Gesell Institute of Child Development (1950–8). He devised standard scales for measuring the progress of infant development, supplementing his writing with extensive use of film. His books include An Atlas of Infant Behavior (1934) and Child Development (1949).

Dr Arnold Lucius Gesell (21 June 1880 - 29 May 1961) was a pioneer in the field of child development. His set of normal milestones for children is still widely used by pediatricians, psychologists and other professionals who work with children. At Yale, he started fairly soon with a clinic of child development, and between 1915 and 1948 he was professor of child hygiene at Yale.

He worked on feral children and adoption, but his main interest was the normal development of children. To this end he constructed the Gesell dome, a one-way mirror shaped as a dome, under which children could be observed without being disturbed.