von Osten's horse

n. A horse which was famous in the early 1900s for being able to give the correct answer to any question its owner asked of it by tapping its hooves on the ground. It was eventually found that Clever Hans could only answer questions to which his owner knew the answer and only when he could see his owner. It was eventually assumed by scientists that the owner was unconsciously giving Hans subtle cues. This story has been used ever since that time as an example of reaching false conclusions by overlooking important variables in research. Also known as Clever Hans.