Chimpanzees (Pan troglodytes) show subtle signs of uncertainty when choices are more difficult

Abstract

Humans can tell when they find a task difficult. Subtle uncertainty behaviors like changes in motor speed and muscle tension precede and affect these experiences. Theories of animal metacognition likewise stress the importance of endogenous signals of uncertainty as cues that motivate metacognitive behaviors. However, while researchers have investigated second-order behaviors like information seeking and declining difficult trials in nonhuman animals, they have devoted little attention to the behaviors that express the cognitive conflict that gives rise to such behaviors in the first place. Here we explored whether three chimpanzees would, like humans, show hand wavering more when faced with more difficult choices in a touch screen transitive inference task. While accuracy was very high across all conditions, all chimpanzees wavered more frequently in trials that were objectively more difficult, demonstrating a signature behavior which accompanies experiences of difficulty in humans. This lends plausibility to the idea that feelings of uncertainty, like other emotions, can be studied in nonhuman animals. We propose to routinely assess uncertainty behaviors to inform models of procedural metacognition in nonhuman animals.

Keywords: Chimpanzees; Epistemic emotions; Feelings of uncertainty; Procedural metacognition; Transitive inference.

Fig. 1

Top: the five image stimuli used as list items. Bottom: example trial with required clearing order. For details, see text.

Fig. 2

Effects of (a) magnitude and (b) symbolic distance of subset pairs on chimpanzees' number of wavering movements throughout the trial. Error bars represent confidence intervals (nonparametric bootstrap).

Fig. 3

Effects of (a) magnitude and (b) symbolic distance of subset pairs on chimpanzees' latency to touch the first of the two list items. Error bars represent confidence intervals (nonparametric bootstrap).

Fig. 4

Relationship between (a) magnitude and (b) symbolic distance of subset pairs and chimpanzees' accuracy (proportion correct across trials). Error bars represent confidence intervals (nonparametric bootstrap).