A recent study indicates that certain primates possess geometric reasoning abilities previously believed to be unique to humans. Researchers at Carnegie Mellon University tested rhesus macaques and olive baboons alongside preschool-aged children and adults to compare their understanding of basic geometric concepts.
The study, published last week in the Proceedings of the National Academy of Sciences, involved a shape-matching task designed to be accessible across species and age groups. Participants were shown a geometric figure and asked to identify the same shape from a selection of others that varied in size or orientation. Positive feedback was given for correct matches—treats for monkeys, stickers for children, and verbal affirmation for adults—while incorrect responses received no reward.
Lead author Jialin Li, a cognitive neuroscientist at Carnegie Mellon, explained that the experiment aimed to explore whether geometric understanding is an exclusively human trait or shared more broadly across primates. By including preschoolers with limited formal education and monkeys, the researchers sought to distinguish innate cognitive abilities from those acquired through schooling.
The results demonstrated that both the monkeys and humans could recognize shapes as the same despite variations such as rotation or scaling, suggesting an abstract grasp of properties like symmetry, parallelism, and right angles. Analysis alongside data from a similar experiment by another research team reinforced the conclusion that monkeys, children, and adults can connect shapes by their internal geometric features.
Experts not involved in the study highlighted the significance of these findings. David Freedman, a neurobiologist at the University of Chicago, noted that such tasks engage widespread brain networks responsible for visual and cognitive processing, combining basic perception with higher-level shape recognition. Experimental psychologist Ed Wasserman of the University of Iowa pointed out that many animal species must interpret geometric information to navigate their environments, citing pigeons’ superior shape-matching abilities as an example.
The study challenges long-held assumptions about human uniqueness in geometric cognition. Earl Miller, a neuroscientist at the Massachusetts Institute of Technology, suggested that humans often overestimate their distinctiveness in this regard, observing that consistent recognition of shapes despite perspective changes is essential for navigating a complex world.
Andreas Nieder, an animal physiologist at the University of Tübingen in Germany, described the work as a valuable contribution to understanding the evolutionary roots of geometric intuition. The researchers plan to extend their investigations to determine which specific shapes pose greater difficulty for monkeys and humans alike. These insights could have practical implications for educational strategies in teaching geometry.
By revealing shared cognitive foundations between humans and nonhuman primates, the study offers a fresh perspective on how geometric reasoning evolved and highlights the broad biological basis of this cognitive skill.