Abstract:Paul MacLean, through his scientific research, made significant contributions to the fields of physiology, psychiatry, and brain research. Correspondence, photographs, research materials, reports, writings, and audiovisual materials (1944-1993, 17.5 linear feet) document the official portion of Paul MacLeans career in brain and behavioral research. Through his research at Yale Medical School and at the National Institute of Mental Health, MacLean was instrumental in developing and expounding the theory of the Triune Brain.