[The capacity of dogs to solve problems by operating with the empirical dimensions of figures]

An investigation was made into the dogs capacity for operating with empirical dimensions of figures, i.e. the animal's capacity for solving problems based on the fact that out of two figures a volumetric bait can be placed only in a volumetric figure and not in a flat one. In experiments using two methods (single and multiple presentations of figures, each time of a new pair), the dogs were incapable of solving the problems. They were able, however, to elaborate in the course of learning a visual differentiation of a volumetric figure from a flat one, which implies the formation of a generalization of the volume cue as the only invariant in all the pairs of figures. The investigation into operation with empirical dimensions of figures as one of the objective parameters in estimating elementary reasoning activity of animals indicates that by this criterion dogs range in the philogenetic series by far lower than the previously studied marmoset monkeys and dolphins.