In the first trial of the test, the animal is placed at the end of the start arm and has to choose between the two other arms that are baited. Once the choice made, the subject is removed and after a variable delay, is returned in the start arm. In this second trial, the one arm baited is now the opposite arm to which chosen during the first trial. The animal has to make a different choice than its first one (correct choice) to get the reward.