A project from Robert Hampton and Laboratory of Comparative Primate Cognition at Emory National Primate Research Center will investigate the cognitive capacity for visual mental imagery in nonhuman primates. Humans imagine alternate worlds and futures. Imagining that things can be different is a first step towards making them different. The word imagination refers to creativity and problem-solving and means the capacity to form images. This project aims to determine if this faculty, critical to human reasoning and problem-solving, is shared with nonhuman primates and what causal role it plays in cognition. 

A central challenge in studying imagery is that it is subjective. It is often thought to play an important role in nonhuman cognition, especially since nonhuman animals can't describe their mental imagery through language. Recent research, however, has identified a strong physical sign of imagery in humans: pupil size. Studies show that the vividness of a person’s reported imagery is linked to how much their pupils change when they imagine things of different brightness. For example, pupils constrict when imagining bright objects, such as the sun, and dilate when imagining dim objects, such as the moon. This mirrors what happens during actual perception. Critically, this effect is absent in aphantasic individuals, who self-report a lack of visual imagery, suggesting that pupillary response is a specific marker of imagery vividness.

The project team will use changes in pupil size to test whether rhesus monkeys form visual images.

 The experimental design involves:

1. Presenting monkeys with memoranda of varying luminance (bright vs. dim stimuli)

2. Requiring them to maintain these stimuli in working memory during a delay period.

3. Precisely measuring pupil diameter during this memory retention interval.

If successful, this project could provide evidence to support subjective visual experience in nonhumans which would advance our understanding of nonhuman primate minds and change our understanding of the role of imagery in cognition more generally.