Henry Jackson Watt was born in Aberdeen, Scotland. He first studied philosophy in Aberdeen, but then moved to Carl Stumpf at the University of Berlin. From there he moved to the Würzburg Psychological Institute in 1902, where he completed his doctoral thesis (written in German) under the supervision of Oswald Külpe in 1904. Watt's research was mainly concerned with task-induced mental sets in problem solving.
Watt was a close friend of Albert Holden Abbott, a Canadian student of Oswald Külpe.