Can Animals See Optical Illusions? The Surprising Answer
▼ Summary
– The Ebbinghaus illusion demonstrates context-dependent size perception, where a central circle appears to change size based on surrounding circles.
– Research shows mixed susceptibility to optical illusions in animals, with dolphins and chicks affected but pigeons and baboons not.
– Cats perceive subjective contours like humans, as shown by their susceptibility to the Kanizsa square illusion in studies from 1988 and 2021.
– Ring doves were tested for the Ebbinghaus illusion due to their terrestrial lifestyle and binocular vision, which aids in precise size and distance judgment.
– Guppies were chosen for testing because their aquatic environment requires rapid, global processing to assess relative size for survival.
Many people have seen the Ebbinghaus illusion, where a central circle looks smaller when large circles surround it, and bigger when small ones do. This trick of the eye depends on how our brain interprets surrounding visual information. But are humans the only ones fooled, or can animals fall for optical illusions too? A recent study in Frontiers in Psychology suggests the answer isn’t simple, it varies by species and depends heavily on each animal’s natural habitat and sensory needs.
Earlier studies have shown inconsistent results across the animal kingdom. Dolphins, chicks, and redtail splitfins appear to experience optical illusions, while pigeons, baboons, and gray bamboo snakes do not seem affected. This tells us that susceptibility isn’t universal, it’s tied to how different animals perceive their surroundings.
One of the most familiar examples involves cats and their well-known attraction to boxes and taped squares on the floor. While this “if it fits, I sits” habit is often chalked up to a sense of security in enclosed spaces, it also reveals something about how cats see. Both a 1988 study and a more recent 2021 experiment found that cats perceive the Kanizsa square illusion, meaning they can see imaginary contours just like humans do. This indicates their visual system fills in missing information to form a complete shape.
In the new research, scientists tested ring doves and guppies using the Ebbinghaus illusion. Ring doves live on land, pecking at tiny seeds scattered across the ground. Because of this, researchers predicted the birds would rely on precise, local visual processing, focusing on individual objects rather than analyzing the whole scene. Their binocular vision helps them judge size and distance accurately, but they may not use the surrounding context in the same way humans do.
Guppies, on the other hand, inhabit tropical streams where light flickers through dense plants and predators can appear without warning. Survival here depends on making split-second decisions. For these fish, quickly judging relative size using global processing, taking in the entire visual scene at once, would be a major advantage. This ability is exactly what makes the Ebbinghaus illusion work, suggesting guppies might be susceptible in a way that mirrors human perception.
(Source: Ars Technica)