When he completed his PhD (an experimental investigation of visual perception) Arnheim worked for five years (1928-33) as assistant editor of a cultural affairs magazine published in Berlin. He then moved to the International Institute for Educational Film, League of Nations, in Rome, where he worked in a similar capacity until 1938. A year later found him in London, working as a translator for the BBC (Overseas Service), where he remained for just a year. In 1940 he emigrated to the USA, where he was employed as a research officer (on radio research) at Columbia University, New York. He became an American citizen in 1946. From 1943 to 1968 he was on the Psychology Faculty, Sarah Lawrence College, Bronxville, New York, and was Lecturer and Visiting Professor (Graduate Faculty), at the New School for Social Research, New York. From 1968 until his retirement in 1974 he was Professor of Psychology at the Department of Visual and Environmental Studies at Harvard University, and Visiting Professor at the University of Michigan.

Arnheim';s contributions are in three areas: art perception, art therapy, and visual cognition and problem solving. His approach to psychology was formulated on the thesis that during the Middle Ages, the narrative facts on which Western religions were based at the time of their foundation began to come into conflict with the knowledge of philosophers and later with the discoveries of the natural sciences. This generated a doctrine of the ‘double truth’ - a psychological split between belief and knowledge that persists in modern times. Reconciliation of the split between knowledge and belief can be approached through artistic experience. In his psychology of art Arnheim provided a framework for understanding the theory and practice of expressive arts therapies. He developed a view of artistic behaviour as an aesthetically and cognitively grounded activity that is characterized by a complex interplay between use of a medium and articulation of themes or ideas. Representation rests on the invention of forms that are structurally or dynamically equivalent to an object. Artistic representation does not aim for one-to-one correspondence with an original object. The drawing medium with its specific tools tends to encourage shapes made of lines and contours, and these shapes are the constituents from which a complex graphic language develops. Arnheim drew extensively on Gestalt psychology in the development of this conceptual framework and thereby offered an alternative to neo-behaviourist, cognitive-developmental and psychoanalytic approaches to the arts. His psychology of art provided a conceptual framework which could be extended to accommodate cognition and problem solving more generally. For example, he argued that problem solving proceeds not as a sequence of static stages, but as a process of dynamic changes leading either from an original matrix through deviations, deformations or variations to a more complex structure, or from a distorted structure to a more adequate, simple shape. Thus, problem solving involves the fixating power of percepts: the better the Gestalt, the more firmly a percept will impose itself on the memory, thinking and learning of a percipient.