Information seeking by rhesus monkeys (Macaca mulatta) and capuchin monkeys (Cebus apella)

Abstract

Animal metacognition is an active, growing research area, and one part of metacognition is flexible information-seeking behavior. In Roberts et al. (2009), pigeons failed an intuitive information-seeking task. They basically refused, despite multiple fostering experiments, to view a sample image before attempting to find its match. Roberts et al. concluded that pigeons' lack of an information-seeking capacity reflected their broader lack of metacognition. We report a striking species contrast to pigeons. Eight rhesus macaques and seven capuchin monkeys passed the Roberts et al. test of information seeking-often in their first testing session. Members of both primate species appreciated immediately the lack of information signaled by an occluded sample, and the need for an information-seeking response to manage the situation. In subsequent testing, macaques demonstrated flexible/varied forms of information management. Capuchins did not. The research findings bear on the phylogenetic distribution of metacognition across the vertebrates, and on the underlying psychological requirements for metacognitive and information-seeking performances.

Figure 1

The task from Experiment 1. Monkeys initially were presented with only a covered sample (gray square at top center) and the two information-revealing response options (rectangles at left and right in Panels A and B). The left rectangle (Panel A)—the Reveal Sample response option—disappeared when contacted by the cursor (the dot at center of screen) and revealed the sample image as shown at top right. The right rectangle (panel B)—the Reveal Comparisons response option—disappeared when contacted by the cursor, cleared the screen for 1 s as shown at bottom left, and then revealed the comparison stimuli as shown at bottom right. With the comparison stimuli revealed, the monkey chose one, with the goal to match the sample that had been shown.

Figure 2

Performance by eight macaques in Experiment 1. The diamonds show the percentage of trials on which each monkey chose to see the sample before choosing to see the match choices (independent of the outcome of their response to the matching component). The bars show the percentage of correct matching choices when the sample was either revealed (dark gray bars) or not revealed (light gray bars). The horizontal line indicates the chance level of performance for matching.

Figure 3

The four trial types from Experiment 2. A. The Occluded Sample trial. B. The Revealed Sample trial. C. The Revealed Sample-Revealed Comparisons trial. D. The Occluded Sample-Revealed Comparisons trial. The cursor is the dot at center of the screen that was controlled by the movement of a digital joystick.

Figure 4

The percentages of optimal responses for each trial type in the last session completed by each macaque in each phase of Experiment 2. Each bar indicates a different trial type with its own optimal first response - Reveal Sample responses made to Occluded Sample trials; Reveal Comparisons responses made to Revealed Sample trials; direct matching responses made to Revealed Sample-Revealed Comparisons trials; Reveal Sample responses made to Occluded Sample-Revealed Comparisons trials.

Figure 5

Percentage of trials on which four rhesus monkeys made the optimal information-seeking response. Each bar shows performance on the first 20 trials of that trial type in that phase. Asterisks indicate performance that exceeded chance levels (chance was 50% for the Occluded Sample and Revealed Sample conditions, and chance was set conservatively at 33% for the Revealed Sample – Revealed Comparisons and Occluded Sample – Revealed Comparisons conditions because the monkey could initially choose the Reveal Sample, Reveal Comparisons, or direct matching response).

Figure 6

The percentages of optimal response for each trial type in the last session completed by each capuchin in each phase of Experiment 3. Each bar indicates a different trial type with its own optimal first response - Reveal Sample responses made to Occluded Sample trials; Reveal Comparisons responses made to Revealed Sample trials; direct matching responses made to Revealed Sample-Revealed Comparisons trials; Reveal Sample responses made to Occluded Sample-Revealed Comparisons trials.