Despite his mother beckoning him to come towards her, this infant hesitates to cross the "visual cliff" – an apparently steep drop that is actually covered by transparent glass. Psychologists in the 1960s found that most infants 6 to 14 months of age were reluctant to crawl over the cliff, suggesting they had the ability to perceive depth. Most psychologists believe that the ability to perceive depth is partly innate and partly a product of early visual experience.

Here's a test you can try to demonstrate how your perception of depth is still live and active. Below are two perfect circles, yet the smaller circle appears distorted. Our brain interprets the converging lines to be adding depth to the screen, as if the solid middle is further aw ...

At some point in your life, you've probably played this game of logic known as the missing square puzzle, or Curry's paradox - named after its inventor Paul Curry. This optical illusion is commonly used in mathematics classes to help students reason about geometrical figures, or rather to teach them to not reason using figures, but only using the textual description thereof and the axioms of geometry. It depicts two arrangements made of similar shapes in slightly different configurations. Each apparently forms a 13×5 right-angled triangle, but one has a 1×1 hole in it.

As depicted in the animation, the illusion works because the diagonal of the two internal triangles is not a continuous slope from corner to corner. The overall connected shap ...

This type of optical illusion plays with our brain’s sense of perspective: the dragon’s face looks like it’s sticking out toward us because, after all, we know from a life time of experience that faces stick out instead of cave in.

But the exact opposite is actually the case here. Regardless of what you perceive, the entire face of this dragon is inverted making everything backwards: For example, the right eye is actually farther away from us than the left eye, and it’s this inversion that confuses our brains and makes us think the dragon is staring at us.

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This video offers up one of the strongest natural hallucinatory illusions we've ever experienced.

"We don't live in a world of reality but a world of perception." Try to read every letter on the screen...

The Schiller Effect (aventurescence) is an optical illusion that makes stones such as labradorite appear to light up internally. The layering of different minerals at a scale near the wavelength of light causes the scattering and interference effect.

This double red rainbow was photographed over a Greek sunset by Manolis Thravalos. The optical phenomena is a result of Rayleigh scattering, which is the scattering of light by tiny particles in the atmosphere. This scattering is what causes the Sun to appear yellow and the sky to appear blue, and also results in red sunsets where the atmosphere is thicker around the horizon.

You see those embedded spirals of green, pink and blue? The green and blue spirals are actually the exact same colour.

When the green and pink colours are placed side-by-side, they enhance each other’s darker tones, making them look like completely new colours. How we perceive colours is dependant on the light and shadow surrounding them and on the placing of contrasting colours side by side.

Can you spot the snow leopard in this picture? If you were its prey, you'd already be dead.

Camouflage win.

Wait, still can't find it? Look here.