Perception of novel changes in a familiar environment by socially-housed rhesus monkeys

Many animals appear to have a sophisticated spatial representation of their environment. The development of these representations depends on the joint abilities of discriminating novel objects and remembering their locations. Variations of a detection of novelty paradigm were used to determine the nature and limitations of these abilities in rhesus monkeys. Socially-housed monkeys at two facilities (UMASS Primate Laboratory and the New England Regional Primate Research Center) were exposed to novelty detection tasks using a vertical object grid arranged on a mesh wall of the animals' pens. Monkeys rapidly responded with increased exploration to the replacement of one familiar object with a novel object, to the movement of a familiar object to a novel location, and to the swapping of two familiar objects. However, novelty of object was more salient than novelty of place. In these initial studies, monkeys were given continuous access to the grid, and only one or two changes occurred on a given day. In subsequent studies, the task difficulty was varied either by reducing the length of grid exposure or increasing the number of changed objects/session. Surprisingly, only a reduction in length of exposure markedly affected novelty detecting abilities. Rhesus monkeys clearly possessed the dual novelty detecting abilities. These skills were negatively affected only when monkeys' access to the grid was limited. The procedure employed here provided a convenient way to assess complex cognitive abilities in a group setting. It also relied on rhesus monkeys' inherent attraction to novelty and required only their species-typical behavior for assessment.