Most likely, you are encountering some version of “Ebbinghaus illusion“, in which the central circle appears smaller when it is surrounded by larger circles, and appears larger when it is surrounded by smaller circles. This is an example of context-sensitive size perception. But is this unique to humans or are some animals susceptible too? According to new paper published in the journal Frontiers in Psychology, this may depend on the specific sensory environment, since the effectiveness of the illusion depends on contextual cues.
According to the authors, previous studies have yielded mixed results on the issue of animals and their susceptibility to optical illusions. For example, dolphins, chicks, and red-tailed splitfins appear susceptible, while pigeons, baboons, and gray bamboo snakes do not.
Perhaps the most famous example is cats' undoubted love for boxes and squares, an “if it fits, I’ll sit” phenomenon documented all over the internet. This behavior usually attributed to the fact that cats feel safer when they're confined to small spaces, but it also tells us something about a cat's visual perception. 1988 study And 2021 study concluded that cats are susceptible to The illusion of Kanizsa Squarewhich suggests that they perceive subjective contours in the same way as humans.
