There is also another interval during which the divider is removed and the monkey can access the objects and obtain the food reward. For this period of time, the primate is allowed to manipulate the objects in an attempt to obtain the reward, during which time the observer is able to collect additional observational data on the primate’s behavior. The Wisconsin General Test Apparatus is used to test the learning capabilities of monkeys. The subject, usually a primate, is contained in the half of the apparatus that functions as a cage. Here the primate and observer are able to be kept safe during different intervals of observation. Numerous tests including black-white discrimination and reversal tests and two-choice object discrimination tests have utilized the Wisconsin General Test Apparatus. The device has also been modified for other uses. These include but are not limited to modifications for: use with rats, use with smaller primates, a semi-automatic function, and for improved portability.