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. 2015 Sep:142:236-46.
doi: 10.1016/j.cognition.2015.05.023. Epub 2015 Jun 6.

Go when you know: Chimpanzees' confidence movements reflect their responses in a computerized memory task

Michael J Beran  1 , Bonnie M Perdue  2 , Sara E Futch  3 , J David Smith  4 , Theodore A Evans  5 , Audrey E Parrish  6
Affiliations

Go when you know: Chimpanzees' confidence movements reflect their responses in a computerized memory task

Michael J Beran et al. Cognition. 2015 Sep.

Abstract

Three chimpanzees performed a computerized memory task in which auditory feedback about the accuracy of each response was delayed. The delivery of food rewards for correct responses also was delayed and occurred in a separate location from the response. Crucially, if the chimpanzees did not move to the reward-delivery site before food was dispensed, the reward was lost and could not be recovered. Chimpanzees were significantly more likely to move to the dispenser on trials they had completed correctly than on those they had completed incorrectly, and these movements occurred before any external feedback about the outcome of their responses. Thus, chimpanzees moved (or not) on the basis of their confidence in their responses, and these confidence movements aligned closely with objective task performance. These untrained, spontaneous confidence judgments demonstrated that chimpanzees monitored their own states of knowing and not knowing and adjusted their behavior accordingly.

Keywords: Chimpanzees; Confidence judgments; Matching-to-sample; Memory; Metacognition.

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Figures

Figure 1
Figure 1
A schematic of the testing area within the larger chimpanzee housing area. Sections shown in grey housed the chimpanzees, and three enclosures were used, each of which connected to the adjacent enclosure by a doorway through which the chimpanzees could move. TV shows the area in which the experimenters observed ongoing test sessions via a closed-circuit monitor, and this area was behind an opaque wall that kept chimpanzees from seeing them (the dark vertical line). J represents where the joystick and computer apparatus were setup, and D represents the two locations where the dispenser could be located depending on how far the chimpanzees had to move to retrieve food rewards. C represents the location of the camera that recorded the chimpanzees.
Figure 2
Figure 2
The performance of Lana and Sherman in Experiment 1 in terms of the percentage of trials in which they moved early to the food dispenser, shown for correctly completed trials and incorrectly completed trials.
Figure 3
Figure 3
The performance of Lana and Sherman in Experiment 2. The top panel shows the percentage of correct matching choices as a function of the retention interval between presentation of the sample and match choices. The bottom panel shows the percentage of trials in which they moved early to the food dispenser, shown for correctly completed trials and incorrectly completed trials.
Figure 4
Figure 4
The performance of Lana and Sherman in Experiment 3. The top panel shows the percentage of correct matching choices as a function of the retention interval between presentation of the sample and match choices, including for trials with no sample. The bottom panel shows the percentage of trials in which they moved early, shown for correctly completed trials and incorrectly completed trials with samples, and for trials without a sample.
Figure 5
Figure 5
The performance of Lana in Experiment 4. The top panel shows Lana’s percentage of correct matching choices as a function of the retention interval between presentation of the sample and match choices for sessions where she had to move only to an adjacent cage or two cages away. The bottom panel shows the percentage of trials in which she moved early, shown for correctly completed trials and incorrectly completed trials with samples, and for trials without a sample, and as a function of how far she had to move.
Figure 6
Figure 6
The performance of Mercury in Experiment 5. The top panel shows the percentage of correct matching choices as a function of the retention interval between presentation of the sample and match choices, including for trials with no sample. The bottom panel shows the percentage of trials in which Mercury moved early, shown for correctly completed trials and incorrectly completed trials with samples, and for trials without a sample.
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