DISTINGUISHING INTENTIONAL FROM ACCIDENTAL ACTIONS IN ORANGUTANS (PONGO-PYGMAEUS), CHIMPANZEES (PAN-TROGLODYTES), AND HUMAN CHILDREN (HOMO-SAPIENS)

This study investigates the understanding of others' intentions in 2- and 3-year-old children, chimpanzees (Pan troglodytes), and orangutans (Pongo pygmaeus). During training, subjects learned to use a discrimi native cue to select a baited box. During testing, the experimenter pl aced a marker on top of the baited box to inform the subject of the re ward's location. However, the experimenter also accidentally dropped t he marker on top of an unbaited box, so that during any given trial th e experimenter marked 2 boxes, 1 intentionally and 1 accidentally. All 3 species preferentially selected the box the experimenter had marked intentionally (especially during the initial trials), with 3-year-old children presenting the most robust results. These findings suggest t hat subjects understood something about the experimenter's intentions. The authors speculate that understanding of others' intentions may pr ecede the understanding of others' beliefs both at the ontogenetic and phylogenetic levels.