I'm going to show you some images and you're going to have to make some quick decisions.
Is line a or line b longer? Is the horizontal or vertical line longer? Is the top or bottom line longer?
Keep looking...
In all of these images they're actually the same length. You may have seen these before—
but you're more susceptible to be tricked by these illusions — or not —
depending on where you live.
Two studies 50 years apart showed that non-Western people were less likely to be tricked by the
Müller-Lyer or Parallelogram illusion than Europeans and Americans.
And they were more susceptible to the horizontal-vertical illusion.
The researchers suggest that the physical environment you live in shapes your
susceptibility to certain illusions.
illusion because you're not as familiar with seeing vertical and horizontal objects at
Urban dwellers are moderately susceptible
and people who live in restricted environments, like a dense forest,
or a big city, aren't as easily tricked. There's plenty of straight line things around for
us to develop a frame of reference, like tall buildings or trees.
It's mind blowing to think that the visual experiences you've had in life affects your
perception of objects.
Our basic biological process of seeing something like these lines is the same,
but we've all developed different habits of how we perceive them.
And experiments have manipulated the process of how we see objects.
In cats. In cats wearing an eyepatch.
In one study, a kitten reared with an eyepatch over one eye for 6 months had
impaired depth perception.
The cat still had two normal eyes, but a greater area of the visual cortex was devoted to analysing
information from the unpatched eye than the patched eye.
Another study went a whisker further. Researchers raised two groups of kittens in the dark,
and when they were exposed to light they wore goggles that restricted them to see
in either horizontal lines or vertical lines.
When the goggles were removed, the cats were blind to lines running the other way.
The horizontal cats could sit on a chair, but would bump into the chair’s legs. The
vertical cats could avoid the chair legs, but missed
when they tried to jump on the chair.
The researchers discovered the visual cortex contains nerve cells called “feature detectors”
– they respond only when we’re shown a line with a certain orientation,
like horizontal or vertical.
The cat’s brains dedicated these nerve cells to one orientation and neglected the other.
Just like the influence of where we live, the early visual experiences of the cats
shaped how they perceived the physical world.
So, were you tricked by these illusions?
Let me know down if the comments if you were and what kind of environment you're from.
And remember that in those studies I mentioned they're observed as an effect over lots of
people. So it doesn't necessarily mean that if you're from a city you're going to be
more or less tricked by an illusion.
But, if enough people comment maybe we observe an effect from the people that
watch this video. So let me know.