William Dunlop Tait was head of the Psychology Department at McGill University. from 1924 to his death in 1944. He was from Nova Scotia, where he earned a Bachelor's degree at Dalhousie University, but he went south for graduate work, taking a PhD at Harvard University under the supervision of Hugo Münsterberg. He was appointed to a Lectureship in the Philosophy Department at McGill in 1909, and he founded McGill's first experimental psychology laboratory in 1910. He was promoted to Assistant Professor in 1914, but clashed mightily with the Head of Philosophy, William Caldwell. In April of 1924, the university president, Arthur Currie, agreed to Tait's long demand that psychology be separated from Philosophy and given its own Department. Simultaneously, Tait was also promoted to Professor and made Head of Psychology.

Although he was responsible for bringing experimental psychology to McGill, Tait's work was mostly applied in character, focused especially on educational psychology.

After Tait's death, McGill psychology saw a rapid succession of leaders. Tait's long-time assistant, Chester E. Kellogg, became Acting Chair in 1944. In 1946, Robert B. MacLeod was brought in to chair the department on a permanent basis, but left for Cornell University just two years later. One of MacLeod's key hires, during his short time at McGill, however, was Donald O. Hebb, who succeeded him as Chair of the McGill Psychology Department in 1948.