Estimating and operating on discrete quantities in orangutans (Pongo pygmaeus).
This study investigated the ability of 3 male orangutans (Pongo pygmaeus; 1 subadult, 2 adults) to estimate, compare, and operate on 2 sets of small quantities (1-6 cereal bits). Experiment 1 investigated the orangutans' ability to choose the larger of 2 quantities when they were presented successively as opposed to simultaneously, thus being perceptually unavailable at the time of choice. Experiment 2 investigated the orangutans' ability to select the larger quantity after the original quantities were augmented or reduced. Orangutans were capable of selecting the larger of 2 quantities in Experiment 1. There was also some evidence from Experiment 2, albeit weaker, that orangutans may mentally combine quantities (but not dissociate) to obtain the larger of 2 quantities. This study suggests that orangutans use a representational mechanism (especially when comparing quantities) to select the larger of 2 sets of items.
Call
J
J
Max-Planck-Institute for Evolutionary Anthropology, Leipzig, Germany. call@eva.mpg.de
D000818:Animals; D002755:Choice Behavior; D006801:Humans; D008297:Male; D008570:Memory, Short-Term; D011148:Pongo pygmaeus / Q000523:psychology*; D012858:Size Perception