Susie wants to use operant conditioning to teach her cat to sit up for a treat. a psychologist who has conducted research that would be useful to her in this situation is

The correct answer is
Edward Thorndike

He was a famous American Psychologist from the first half of the 20th century who kind of revolutionized behaviorism and was important for developing psychology in the United States, most famous for his Law of Effect which is still used today and analyzed.