Optical illusions which circle is bigger

The illusion rests on the fact that the visual-attention system uses context to determine the size of objects. The orange circle on the left is surrounded by larger circles, making it seem small by comparison. The one on the right is surrounded by smaller circles, making it seem big.

Interestingly, adults who fall for the illusion visually tend not to succumb if asked to reach for the two objects. Although their eyes are telling them that the circles are different sizes, their grip size is the same in both cases. This has been used as evidence that there are two separate pathways for vision in the brain, one used for identifying objects and the other used for action. The illusion feels fast and automatic yet is surprisingly susceptible to individual differences.

Although most people across cultures experience the illusion, it is stronger for those from Japan than those from the UK. This cultural difference interacts with other factors: the effect is stronger on average in women than men though there is massive overlap and in social scientists than in mathematicians. These differences are thought to rest on processing style.

Those who experience the illusion most strongly tend to have a more global, holistic processing style as compared to a more local, analytic style. Interestingly, children below the age of 7 do not seem to experience the illusion, regardless of where they come from. No-one is quite sure why but it may be because it relies on familiarity with depth cues in printed images. Contact the author here.

Republicans and Democrats have both made appearances in Glasgow for the giant climate conference. The quasar J is 13 billion light-years away from Earth.

But it still can reveal a lot about our own universe. Brighstoneus simmondsi has a big lump around the nostrils, like a chunky alligator. Sign up to receive Popular Science's emails and get the highlights. Head Trip. That exercise illustrates the difference between the monocular cues your brain uses when looking at 2D images as opposed to binocular cues it uses for 3D images.

Monocular cues only provide relative depth based on other objects in the environment, such as the size of the circles in the image above. The brain fills in ambiguous blanks based on context.

This is how your eyes confuse your brain with relative size optical illusions. Your eyes know your brain will rely on monocular cues! If you close one eye and look around, you can perceive depth, but size and distance are ambiguous.