What famous psychologist did research on enuresis and classical conditioning?

A Russian psychologist in early 1990s, Ivan Petrovich Pavlov is the famous psychologist who did research on enuresis and classical conditioning. Enuresis or the involuntary urination, especially by children at night alarms work on the principle of Conditioned Learning, a type of learning in which one learns to link two or more stimuli and anticipate events.