Clever Hans was an Orlov Trotter

Orlov Trotter

The Orlov Trotter is a horse breed with a hereditary fast trot, noted for its outstanding speed and stamina. It is the most famous Russian horse. The breed was developed in Russia in the late 18th century by Count Alexei Orlov at his Khrenovskoy Stud farm near the town of Bobrov...

 horse

Horse

The horse is one of two extant subspecies of Equus ferus, or the wild horse. It is a single-hooved mammal belonging to the taxonomic family Equidae. The horse has evolved over the past 45 to 55 million years from a small multi-toed creature into the large, single-toed animal of today...

 that was claimed to have been able to perform arithmetic

Elementary arithmetic

Elementary arithmetic is the simplified portion of arithmetic which is considered necessary and appropriate during primary education. It includes the operations of addition, subtraction, multiplication, and division. It is taught in elementary school....

 and other intellectual tasks.

After a formal investigation in 1907, psychologist

Psychologist

Psychologist is a professional or academic title used by individuals who are either:* Clinical professionals who work with patients in a variety of therapeutic contexts .* Scientists conducting psychological research or teaching psychology in a college...

 Oskar Pfungst

Oskar Pfungst

Oskar Pfungst was a German comparative biologist and psychologist. While working as a volunteer assistant in the laboratory of Carl Stumpf in Berlin, Pfungst was asked to investigate the horse known as Clever Hans, who could apparently solved a wide array of arithmetic problems set to it by its...

 demonstrated that the horse was not actually performing these mental tasks, but was watching the reaction of his human observers. Pfungst discovered this artifact in the research methodology, wherein the horse was responding directly to involuntary cues in the body language

Body language

Body language is a form of non-verbal communication, which consists of body posture, gestures, facial expressions, and eye movements. Humans send and interpret such signals almost entirely subconsciously....

 of the human trainer, who had the faculties to solve each problem.