PERCEPTUAL STRATEGIES IN THE ESTIMATION OF PHYSICAL QUANTITIES BY ORANGUTANS (PONGO-PYGMAEUS)

The perceptual strategies used by 4 orangutans (2 subadults, 2 adults) when choosing the larger of 2 volumes in a Piagetian conservation tas k were investigated. Three possible perceptual strategies were investi gated: (a) direct perceptual estimation of the container's content ind ependent of its shape, (b) use of the spatial and temporal cues provid ed by the pouring of liquid from one container to another, and (c) abi lity to initially identify the larger volume and track it across trans formations disregarding misleading perceptual-cues. Results indicated that the direct perceptual estimation strategy was the best candidate to explain the orangutan's systematic choice of the larger of 2 quanti ties.