Under the umbrella of comparative cognition is an animal’s ability to understand quantity or numerosity. In the late 1800s a German math teacher successfully taught his horse Hans how to answer mathematical questions by tapping his hoof on the ground. He could answer addition and subtraction problems and could keep track of dates on the calendar. A psychologist, Oskar Pfungst was very skeptical and observed Hans doing his tricks. He found that Hans could not solve mathematical equations but instead was very good at reading facial features of the questioner. If Hans was asked to tap out the answer to 2 + 3, he would start tapping, the questioner would begin counting and unconsciously dip their head or move some part of their body, this would signal to Hans that many taps was the correct answer. In all of this, Hans was portraying a precise form of stimulus discrimination, but it is impressive, nonetheless. Similar to Hans clever acts is Maggie the Jack Russell who, in the video, is up against 7-year-olds in a mathematical competition that is very amusing to see.