 His first faculty appointment (1975) was as a Lecturer, and promoted to Assistant Professor in 1976 in the Departments of Biology and Psychology at Harvard University; promotion to Associate Professor followed (1979).Throughout his tenure he was an Associate at the Museum of Comparative Zoology.In 1982, he joined the faculty of the Department of Zoology (now Integrative Biology) at the University of Texas at Austin; he became the Ashbel Smith Professor of Zoology and Psychology in 1998.