Name: How Optical Illusions Work
Uploaded: 2025-06-17T14:35:12.000Z
Duration: 4 min 9 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

Where do you see the midpoint of this line?

Most people see the center of the line left of the actual midpoint.

While those who get tricked wonder how much they can trust their own eyes, it is those who don't see the optical illusion that is science's real mystery, but first things first.

The Müller-Lyer illusion and its most famous form features two lines, each flanked by a set of opposing arrows, which tricks you into thinking that one line looks shorter because the other appears further away, when in fact, they are exactly the same.

The effect is the result of our perception of three-dimensional space, where the inward-pointing arrows are perceived as further away, while outward pointing ones seem closer and shorter.

And because you probably grew up in three-dimensional spaces full of right angles, your brain, in an attempt to make sense of these cues, can get fooled by a two-dimensional illustration.

Like most social science, the research was mostly conducted with people who are weird, Western, educated, industrialized, rich, and from a democratic country, that is.

And so some scientists wondered whether it would work on people who are raised in environments with no rectangular architecture.

And so in the 1960s, two researchers and one of their students began investigating the illusion's effect on people from all over the world, 17 different cultures in total.

People who grew up in spaces with clear corners were fooled most of the time.

Whereas Bushmen from Southern Africa, tribes people from Angola, and Kalahari hunter gatherers almost always perceive the lines as identical.

The researchers concluded that our perception is not a reflection of reality, but a construction shaped by minds who experienced growing up in a particular culture.

This makes sense since it's during the early years of life that our brains are highly receptive to environmental stimuli and capable of forming new neural connections at a rapid pace.

This part of our life is known as the critical period because the most relevant cognitive functions develop right then.

If we look, for example, at a child's rate of synaptic formation over the first 11 months and the following years, we can see that the speed at which each new connection for vision and hearing is created peaks at around three to four months of age.

For language, that's around month eight, and higher cognitive functions like decision making at age two to three.

In other words, the experiences children have during the first years of life can significantly impact the construction of their brains, all up to the point that they literally see the world differently.

And what's behind the checker shadow trick, where two squares appear to be different shades of gray, but are exactly the same.

And if not, is that because you aren't weird?

Tell us your thoughts and experiences in the comments below.

We relentlessly researched education for the past decade, read plenty of peer-reviewed papers, visited all sorts of schools, created hundreds of videos on the topic, and even set up our very own kindergarten for project-based learning, and now, we also made a book.

The Unschooler's Educational Dictionary covers everything we know about learning, unveils the unintended consequences of compulsory education, and includes a complete guide to the alternative school movement.

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