Is It A Rabbit Or A Duck? Here's Why Optical Illusions Trick Us

This animated video explains why your brain takes short cuts to construct a visual world on the fly.

by Zach Sokol

August 12, 2014, 5:20pm

Lead image via

Is it a duck, or is it a rabbit? From the ambiguous animal illustration, to countless other optical illusions, our brains are receptive to visual tricks, but it can be tough to articulate why. In a TED-Ed video by Nathan S. Jacobs titled "How Optical Illusions Trick Your Brain," the educator explains the biological aspects behind how humans perceive, say, convexities and concavities in a 2D drawing, depending on the picture's orientation.

In the entertaining five-minute animated short (below), Jacobs breaks down three classic optical illusions, explaining that they reveal the "brain's job as a busy director of 3D animation in a studio inside your skull, allocating cognitive energy and constructing a world on the fly with tried and mostly, but not always, true tricks of its own."

Without recapping the whole clip, one optical illusion explanation stands out in particular. Jacobs showcases two photos of Abraham Lincoln, one right-side up, the other upside down. Next to one another, both images look normal, but when the flipped one gets properly orientated, Lincoln's face suddenly looks askew.

The video explains that profiles trigger activity in the brain that are specifically evolved to help us recognize faces, such as the fusiform face area and occipital and temporal lobes. When humans encounter faces, we have to process them (and what they're expressing) very quickly, so we're developed to look straight at the eyes and mouth.

In this particular illusion, the flipped Lincoln's eyes and mouth are actually right-side up. So when it gets orientated, the most important parts of the face get turned 180 degrees and we realize that something isn't right. "Your brain had taken a short cut and missed something," explains Jacobs. "It wasn't being lazy, your brain is just very busy and spends cognitive energy as efficiently as possible, using assumptions about visual information to create a tailored, edited vision of the world."

Though these cerebral responses might sound obvious, the TED clip articulates these visual phenomena in a succinct and digestible manner. Now we know why we see both the duck and the rabbit—though we're no closer to figuring out what seeing one of these two creatures first says about our personalities. This is cognitive science, not cognitive therapy, after all.