Overview
- The paper published in PNAS on July 20, 2026 reports touchscreen shape-matching experiments with eight adult monkeys (four rhesus macaques and four olive baboons), 55 U.S. preschoolers, and 77 minimally schooled Tsimane' adults.
- Researchers found monkeys’ choices overlapped substantially with preschoolers’ and landed on a continuum with adults, while adults showed stronger use of symbolic geometric features consistent with effects of formal schooling.
- When sample shapes were rotated, a subset of monkeys and preschoolers shifted sharply toward rotation-invariant, symbolic-style representations, leading authors to say task demands—not species alone—can trigger categorical changes in how shapes are represented.
- The team compared behavior to three computational models (pixel-level similarity, holistic shape recognition, and a symbolic feature model) and concluded monkeys were sensitive to abstract features like symmetry and parallelism rather than relying only on simple visual matching.
- The authors released data, code, and videos but caution that the small nonhuman sample, high correlation between the symbolic and rotation-invariant models, and differences in prior touchscreen experience limit broad generalization even as the results point to deep, shared roots of geometric intuition in primates.