Perception of complex geometric figures in chimpanzees (Pan troglodytes) and humans (Homo sapiens): Analyses of visual similarity on the basis of choice reaction time.
Masaki Tomonaga, Tetsuro Matsuzawa
In a conditional-discrimination task (matching-to-sample), assessed similarities among figures consisting of 2 elemental figures through the choice reaction time (RT), nonmetric multidimensional scaling, and hierarchical cluster analysis of data from chimpanzees ( Pan troglodytes) and humans ( Homo sapiens). Humans also rated similarities among figures. The results of the 3 experiments clearly indicated that the RT data obtained from chimpanzees' performances were useful measures of the similarities among figures. The results suggested that chimpanzees and humans perceived the complex figures similarly. The outer-contour elements were perceived most dominantly by both species, and the straight-line elements were perceived least dominantly. Both species showed the same perceptual hierarchy or dominance among perceptual categories, as determined by the similarity of simple elements, on the basis of transformational invariances.