He attended the University of Berlin under the supervision of Carl Stumpf in 1901–1902, but then moved on to Külpe and Würzburg, where he completed his doctorate in 1906.
Watt's dissertation was on thought processes and problem solving (Experimentelle Beiträge zu einer Theorie des Denkens).
An English abstract of his dissertation appeared in the journal article "Experimental Contribution to a Theory of Thinking" (1906).
He was visiting Würzburg in 1914 when World War I broke out, and was interned in a civilian prisoners camp.
Two additional books were published posthumously: The Sensory Basis and Structure of Knowledge (1925) and The Common Sense of Dreams (1929).