Researchers have discovered that macaques experience the uncanny valley effect — a phenomenon previously documented only in humans — using a new deep-learning tool called “MacAction” that creates realistic 3D monkey avatars.

The team showed eight male rhesus macaques videos of real monkeys alongside animated avatars performing identical movements. The monkeys’ viewing patterns were nearly identical between the real and animated versions, indicating a high perception of realism.

When the scientists systematically reduced avatar realism by stripping away fur, color, and texture, the macaques fixated less frequently on intermediate-realism avatars compared to both the highly realistic and the very unrealistic versions — the characteristic U-shaped response associated with the uncanny valley.

“Monkeys, just like humans, respond to realistic body avatars similarly as to real videos,” the research team explained, noting that the animals demonstrate an uncanny valley effect similar to that seen in people.

Journal: PLOS Biology
DOI: 10.1371/journal.pbio.3003880
Publication Date: July 14, 2026

Source: EurekAlert