Can horses really do math?

At the end of the nineteenth century, a performing horse in Germany known as Clever (or Kluge) Hans was able to tap out the answers to mathematical problems written on a chalk board. Hans would use his right forefoot to indicate the single digits (0-9) and his left forefoot for the tens place (10, 20, 30, etc.). His amazing performances continued for a number of years until the psychologist Oskar Pfungst (1874-1932) was able to show that Hans was simply counting until his questioner indicated (subconsciously) that Hans had reached the correct sum. Even though the horse was not actually performing calculations, his ability to observe and respond to subtle changes in human behavior is still quite noteworthy.

Previous question:	Why will my dog play fetch but not my cat?
Next question:	Who was Mr. Ed?

---