Dr Claudia Uller, of the University of Essex, inspired by the story of Clever Hans, a horse that caused a sensation 100 years ago with his apparent abilities to simple arithmetic and keep track of the calendar investigated whether horses could count. In public performances in Germany he is said to have communicated the answers to questions by tapping his foot "However, psychologist Oskar Pfungst carried out an investigation and reported in 1911 that Clever Hans was not performing arithmetic, but had learnt to obtain the required answers by interpreting the reactions of his maths teacher owner and other observers.
"However, our results suggest that horses too, and not only primates, are able to spontaneously discriminate between two small numbers." Dr Uller and his colleague Jennifer Lewis carried out a series of experiments involving privately owned horses stabled near Colchester, Essex.
In one task, 11 of 13 horses consistently selected buckets containing three plastic apples over another containing two when offered a choice. Fake fruit was used to ensure no difference in smell.
Researchers then showed 12 different horses a box holding either two identical small apples or another containing one large apple with double the surface area. Again, all but two selected the greater number of apples.