LIQUID CONSERVATION IN ORANGUTANS (PONGO-PYGMAEUS) AND HUMANS (HOMO-SAPIENS) - INDIVIDUAL-DIFFERENCES AND PERCEPTUAL STRATEGIES

Four orangutans (1 juvenile, 2 subadults, and 1 adult) and ten 6-8-yea r-old children were tested in 4 liquid conservation tasks of increasin g levels of difficulty. Task difficulty depended on the type of transf ormation (continuous vs. discontinuous quantities) and the relative co ntrast between the shapes of the containers. Results indicate that ora ngutans did not display conservation in the strict sense; instead they showed ''partial'' conservation (intermediate reactions according to J. Piaget & B. Inhelder, 1941). In contrast, some of the children prov ided evidence of conservation in all 4 tasks, showing ''true'' or logi cally necessary conservation in the original sense proposed by J. Piag et and B. Inhelder (1941). Although orangutans did not show conservati on in the strict sense, as J. Piaget (1955) and others have generally agreed it should be defined, orangutans behaved as individual and crea tive problem solvers, adopting different perceptual strategies dependi ng on the task.