Study shows monkeys have optical illusions

It’s also an example of an optical trick known as the “Delbouef illusion”, and until recently, there’s only ever been one study on whether non-human animals perceive it similarly.

A new study carried out by researchers from Georgia State University has revealed that monkeys perceive optical illusions in the same way as humans and great apes do.

Researchers stated the findings point out people and monkeys understand and misperceive the world equally, which displays resemblances in these species’ perceptual techniques and their interpretation of their bodily worlds.

The research experiment involved both humans and monkeys. These dots were sometimes surrounded by Delboeuf rings.

Visual illusions emerge when information is misperceived on the basis of surrounding context or presentation style.

This happens as a result of the ring creates a selected context during which the dots are perceived.

Researchers from Georgia State University performed their study using the Delbouef illusion, a test that involves two equal-sized dots surrounded by different sized rings- an optical illusion that causes the dots to appear different in size.

The research team conducted two computer experiments with human adults and monkeys. The monkeys used a combination of color monitors on PCs and joysticks. In this experiment, it was found that humans perceived the Delboeuf illusion, while no evidence of illusion was observed in case of monkeys. Humans were given a personal computer, computer mouse and digital monitor for the test. Monkeys received training for computerized testing.

Although monkeys may not see the world identically to the way we see it, Parrish said the study indicated “that monkeys are an appropriate model for studying human perception, and that contextual cues affect perception in ways that are shared across species”. The monkeys were rewarded with banana-flavored pellets when they answered correctly.

Humans perceived the Delboeuf illusion, overestimating central dots when small rings surrounded them and underestimating the size of central dots when large rings surrounded them.

For this test, monkeys and humans played a computer game where they were asked to classify the central dots as either “small” or “large”. To handle this concern, they ran a second experiment. Sometimes, a skinny ring of variable measurement surrounded the dot.

Capuchin monkeys and rhesus monkeys, like people, categorized dots introduced inside giant rings as small extra typically than the identical-sized dots introduced inside small rings. The researchers presented several dots encircled in different ring sizes to detect if Delboeuf illusion would still manifest in any of the dot-ring ratios shown.