Who was the clever Hans phenomenon?

The Clever Hans phenomenon refers to a horse named Hans that was claimed to have the ability to perform arithmetic and answer questions by tapping his hoof. The phenomenon illustrated how animals can appear to demonstrate intelligence through cues from their handlers or observers, rather than genuine understanding. Psychologist Oskar Pfungst conducted experiments that revealed Hans was responding to subtle, unintentional signals from people, highlighting the importance of research design and the need for rigorous scientific inquiry. This case has since become a classic example in discussions of animal behavior and the interpretation of intelligence.