Plum take-away

Abstract

After years of hiding plums behind screens on a Puerto Rican island, researchers have concluded that untrained rhesus monkeys are remarkably good at subtraction (Sulkowski, G.M. and Hauser, M.D. (2001) Cognition 79, 239-262]. The researchers wander the island till they spot a lone monkey then, when they are sure the monkey is watching, set up an experimental stage. Different numbers of food and non-food items are placed on two platforms which are then covered. Next, the experimenters very obviously pocket a number of items from one or both of the platforms, leaving a greater number of food items at one location. When free to approach the stage, the monkeys almost invariably head for the platform with more food items. Previous work from the same group established that the monkeys were capable of spontaneous addition and also demonstrated that their abilities are limited to operations on small numbers of items (fewer than four). HJB