He was born Oct. 25, 1931, in St. Louis, Mo., the son of George and Ida (Feldman) Baer. He graduated with honors from the University of Chicago in 1950 and earned a doctorate in experimental psychology there in 1957. His first teaching position was at the University of Washington. He joined the Kansas University faculty in 1965. He was the Roy A. Roberts Distinguished Professor of Human Development and Family Life at KU.

Mr. Baer’s primary discipline was in applied behavior analysis and developmental psychology. His research interests included language, early education, social control imitation, self-regulation and retardation. He advised more than 100 graduate students and taught as a visiting professor at universities in six countries. He also had testified as an expert witness on behalf of parents who sought the best possible education for their autistic children.

The American Psychological Assn. honored him with its Edgar A. Doll Award for distinguished contributions in behavioral science on behalf of people with developmental disabilities. The Association for Behavior Analysis gave him its award for distinguished service to behavioral science. He served as editor and associate editor of the American Journal on Mental Deficiency, and on the editorial boards of 10 other journals.

He married Elsie M. Pinkston. She survives of Chicago.

Other survivors include three daughters, Ruth Baer, Lexington, Ky., Miriam Baer, Durham, N.C., and Deborah Sevart, Franklin, Wis.; and a brother, Robert, Mill Valley, Calif.

The family suggests memorials to the Donald M. Baer Faculty Award through the KU Endowment Association or to KANU-FM, sent in care of Warren-McElwain Mortuary.