Cognitive, Developmental and Social Aspects of Responsiveness To Novel Objects in a Family Group of Marmosets (Sag Uinus Fuscicollis)

Abstract

A breeding pair of S. fuscicollis and their young (total N=6 in the first experiment and 8 in the other three experiments) were housed in a relatively large and heavily vegetated greenhouse and tested on their reactions to novel, innocuous inanimate objects. Some supplementary data were obtained on another such group of four individuals. The animals seemed to know the nature and relative positions of objects in their home environment ; i.e. to be capable of "cognitive mapping". Thus, for example, they detected a single novel object among up to 30 simultaneously presented test objects; they discriminated changes in an object's location and orientation; they responded more to changes in two or more parameters than to changes in only one parameter; and they showed apparent object constancy. These discriminations could be made at almost any randomly-designated location in the greenhouse, and with inter-trial intervals of 23 hours or more. Many aspects of the animals' behavior, including the order in which the various individuals approached a given object, the amount of time they remained at the object, and the likelihood (and order) of their responding to it again on subsequent trials, were highly predictable from their ages. There was, however, no "true" single linear correlation value between age and responsiveness. With appropriate sampling of one's subjects, objects and stages of group habituation, one could in fact find any correlation one chooses, from + 1.00 to -1.00; and age-response functions (and changes therein) were orderly functions of other variables. A breeding pair of S. fuscicollis and their young (total N=6 in the first experiment and 8 in the other three experiments) were housed in a relatively large and heavily vegetated greenhouse and tested on their reactions to novel, innocuous inanimate objects. Some supplementary data were obtained on another such group of four individuals. The animals seemed to know the nature and relative positions of objects in their home environment ; i.e. to be capable of "cognitive mapping". Thus, for example, they detected a single novel object among up to 30 simultaneously presented test objects; they discriminated changes in an object's location and orientation; they responded more to changes in two or more parameters than to changes in only one parameter; and they showed apparent object constancy. These discriminations could be made at almost any randomly-designated location in the greenhouse, and with inter-trial intervals of 23 hours or more. Many aspects of the animals' behavior, including the order in which the various individuals approached a given object, the amount of time they remained at the object, and the likelihood (and order) of their responding to it again on subsequent trials, were highly predictable from their ages. There was, however, no "true" single linear correlation value between age and responsiveness. With appropriate sampling of one's subjects, objects and stages of group habituation, one could in fact find any correlation one chooses, from + 1.00 to -1.00; and age-response functions (and changes therein) were orderly functions of other variables.