Language-trained chimpanzees (Pan troglodytes) name what they have seen but look first at what they have not seen

Abstract

Metacognition can be defined as knowing what one knows, and the question of whether nonhuman animals are metacognitive has driven an intense debate. We tested 3 language-trained chimpanzees in an information-seeking task in which the identity of a food item was the critical piece of information needed to obtain the food. The chimpanzees could either report the identity of the food immediately or first check a container in which the food had been hidden. In two experiments, the chimpanzees were significantly more likely to visit the container first on trials in which they could not know its contents but were more likely to just name the food item without looking into the container on trials in which they had seen its contents. Thus, chimpanzees showed efficient information-seeking behavior that suggested they knew what they had or had not already seen when it was time to name a hidden item.

Keywords: Pan troglodytes; chimpanzees; comparative psychology; decision making; information seeking; metacognition; problem solving.

Figure 1

A schematic of the test area. The areas show in light grey color are indoor housing areas for the chimpanzees. The dark grey areas are outdoor yards for the chimpanzees. P1 (Sherman and Panzee) and P2 (Lana) refer to the locations where the experimenter either showed or did not show the contents of the container initially before moving the container to location C1 (Sherman and Panzee) or C2 (Lana). K1 was the board used by Sherman and Panzee, and K 2 was the keyboard used by Lana to indicate the contents of the container. The dark circles show the starting locations for the chimpanzees, and the dark lines show the routes the chimpanzees had to take if they chose to first view the contents of the container after it was moved before they went to the keyboard to name the item in the container.

Figure 2

Number of responses (moving to the keyboard first or the container first) in each condition of Experiment 1 and Experiment 2 for each chimpanzee.