Rosati_&_Santos-MetacognitionData file for monkey searched in Rosati & Santos (2016) "Spontaneous metacognition in rhesus monkeys." Key for codes included as a separate tab in the file.Video_S1-Twotubes-VisibleVideo S1: Two tubes condition—Visible baiting. In the experimental demonstration, E1 lifts up the two tubes, taps them against each other to show they are empty, and then places them in the v-shaped configuration on the ground in front of the occluder. She then picks up a fake fruit with her right hand and appears to place this fruit on the right distal side opening of one of the tubes (baiting hand and side was counterbalanced across monkeys). She then picks up the occluder and walks away so that the monkey can approach; in the real study she moved behind the camera person (E2). In the example response clip, the monkey approaches and looks in the right side. Note that orientation of video switches: in the demonstration it shows the monkey’s perspective, whereas in the example test clip E2 is behind E1 while she does the demonstration.Video_S2-Twotubes-HiddenVideo S2: Two tubes condition—Hidden baiting. In the experimental demonstration, E1 lifts up the two tubes, taps them against each other to show they are empty, and then places them in the v-shaped configuration on the ground in front of the occluder. Before baiting the tubes, she moves the occluder in front of the tubes (from the monkey’s perspective). She then picks up a fake fruit with her left hand (hand counterbalanced across monkeys) and moved it down; the monkey’s view of the baiting event is then blocked by the occluder. She then picks up the occluder and walks away so that the monkey can approach; in the real study she moved behind the camera person (E2). In the example response clip, the monkey approaches and looks in the center opening of the tubes; in this example, the monkey visibly checks both tubes from this center position. Note that orientation of video switches: in the demonstration it shows the monkey’s perspective, whereas in the example test clip E2 is behind E1 while she does the demonstration.Video_S3-Onetube-VisibleVideo S3: One tube condition—Visible baiting. In the experimental demonstration, E1 lifts up the single tube and tapes it with her hand to show it is empty, and then places it on the ground with the openings perpendicular to the monkey’s perspective She then picks up a fake fruit with her left hand and appears to place this fruit on the side opening (baiting hand and side was counterbalanced across monkeys). She then picks up the occluder and walks away so that the monkey can approach; in the real study she moved behind the camera person (E2). In the example response clip, the monkey approaches and looks in the left side. Note that orientation of video switches: in the demonstration it shows the monkey’s perspective, whereas in the example test clip E2 is behind E1 while she does the demonstration.Video_S4-Onetube-HiddenVideo S4: One tube condition—Hidden baiting. In the experimental demonstration, E1 lifts up the single tube and tapes it with her hand to show it is empty, and then places it on the ground with the openings perpendicular to the monkey’s perspective. She then picks up a fake fruit with her right hand (hand counterbalanced across monkeys) and moved it down; the monkey’s view of the baiting event is then blocked by the occluder. She then picks up the occluder and walks away so that the monkey can approach; in the real study she moved behind the camera person (E2). In the example response clip, the monkey approaches the center location and looks under the tube. Note that orientation of video switches: in the demonstration it shows the monkey’s perspective, whereas in the example test clip E2 is behind E1 while she does the demonstration.Video_S5-Exclusion-InterferenceVideo S5: Example Exclusion—Interference. The target monkey is appropriately centered during the experimenter’s demonstration. E1 leaves so the subject can approach, but a larger male approached from the left side of the screen and displaces the target subject to the side before they can make a choice.Video_S6-Exclusion-LeftVideo S6: Example Exclusion—Left. The target monkey watches the experimenter’s demonstration. E1 leaves so the subject can approach, but the subject runs away before approaching to make a choice.Video_S7-Exclusion-NoApproachVideo S7: Example Exclusion—No Approach. The target monkey watches the experimenter’s demonstration. E1 leaves so the subject can approach, but the subject does not approach for more than 1 minute (timed with a stopwatch). Near the end of this time, the subject begins to groom another monkey who sat near them.

Metacognition is the ability to think about thinking. Although monitoring and controlling one's knowledge is a key feature of human cognition, its evolutionary origins are debated. In the current study, we examined whether rhesus monkeys (Macaca mulatta; N = 120) could make metacognitive inferences in a one-shot decision. Each monkey experienced one of four conditions, observing a human appearing to hide a food reward in an apparatus consisting of either one or two tubes. The monkeys tended to search the correct location when they observed this baiting event, but engaged in information seeking-by peering into a center location where they could check both potential hiding spots-if their view had been occluded and information seeking was possible. The monkeys only occasionally approached the center when information seeking was not possible. These results show that monkeys spontaneously use information about their own knowledge states to solve naturalistic foraging problems, and thus provide the first evidence that nonhumans exhibit information-seeking responses in situations with which they have no prior experience.