Watch Nature Season 1 Episode 11 Online

First there is a re-creation of Ivan Pavlov's experiments which led to the discovery of the "conditioned reflex." Then we see the investigation by Otto Pfungst of "Kluge Hans" (Clever Hans) a horse whose apparent knowledge of arithmetic was actually response to subtle signals from his trainer. We also see dramatizations of Thomdike's experiments with chicks, Watson's with terns, and B. F. Skinner's famed work at Harvard in the thirties.