Five optical illusions: How our eyes deceive us

Discrimination, Illusions, Neurons, Optics

Tuesday, July 26th, 2016

We often rely on what we saw as a means to what we understand as being true.

Optical illusions prove us wrong. They give zero…well, you know what.

We take stories of our friends and what happened to them or someone they know as fact without actually looking into it. Eyewitness testimony is still running rampant with juries of our peers relying on stories to aid them to a conclusion as to what happened somewhere they weren’t.

But how often are our memories wrong? How many times do you look at something and know you saw it, only to find out later it wasn’t ever there at all?

Well, you aren’t the only one to wonder about this, and there’s been some really smart people out there who’ve given us some better answers to our otherworldly questions. Some remarkably smart humans have actually looked at these seemingly magical optical illusions and figured out some explanations for them through science.

Here’s a quick list of five common optical illusions, and proof of why we shouldn’t always hold our memories as truth.

1. Hermann Grid Optical Illusion

So what do you see? If you’re like me, you see a bunch of black squares with white lines in between them…but there’s something else there. In between the squares it looks like there are dots of black sleekly moving around the whitespace just out of my focus.

When I try and focus all my attention on one point, the dots shift around the pattern to everywhere but my focal point. Damn optical illusions.

One explanation for this is what’s known as lateral inhibition, and it shows us just how easily our perception can be deceived.

Lateral inhibition happens because of the setup of the ganglion cells in your eye. As it turns out, when we look at something, the neurons in our eyes have the ability to affect their neighboring neurons by inhibiting their action potential. They take on the extra energy and get supercharged in a sense. This allows them to sharpen their focus, at the cost of neighboring cells of course.

In the Hermann grid, the interacting bands of white cause the most inhibition, leading to the illusion of there being ghostly dots moving around the image.

Here’s a great video explaining the lateral inhibition process if you’d like a pro’s take.

2. The Ponzo Illusion

Ponzo Illusion

The Ponzo optical illusion is a deceptive, yet somewhat easy to understand trick on your mind. The overall takeaway is that the brain takes the background into account when it’s assessing objects in the foreground.

Psychologist Mario Ponzo first demonstrated the idea in 1911 when he drew two equal lines on top railroad tracks, showing us how our environment affects our perception of objects. This whole picture view helps us in our day-to-day as we determine the distance and size of things farther or closer away.

We can see easy demonstrations of optical illusions throughout our lives because we have to constantly judge things according to their environment. You’ve probably just never realized it, because, well, you rely on your vision and memory. But, think of how many times you’ve misjudged how big or small something is.

In the picture above, both yellow lines are equal in length, but the railroad tracks in the background distort the immediate perception to make the top line look larger.

Here’s another example with some cigarettes. Ponzo is everywhere! Sorry, I got excited.

Anyway, this is a great precursor to wrapping your head around some of the next topics like Gestalt psychology and the Moon illusion.

3. Gestalt Psychology

Gestalt Psychology

Credit: Wikipedia

Gestalt psychology takes a parsimonious look at how we perceive things. It explores the idea of how we process images by looking at whole scenes instead of individual parts.

So the Ponzo illusion showed us how we perceive things based off their environment? Gestalt takes optical illusions to a new level. We don’t just judge things according to the space around them, we actually interpret things according to it. Ever see a face in an inanimate object? Don’t worry, we all do.

When things are grouped together, or are similar to one another, they tend to be perceived as a group. We have an inclination to finish unfinished images, like the ones you see above.

We all know there’s no triangle in example A, but all perceive the triangle. The same goes for the spike ball in example C. All of these images are just black objects laid on top of white backgrounds, but what we perceive is so much more.

4. Muller-Lyer Optical Illusion

Muller-Lyer Optical illusion

Credit: Wikipedia

The Muller-Lyer illusion uses our depth perception and size constancy to give us a distorted idea of the world around us. Take the example above. Look at the top three arrows in all black. Disregarding the faux arrow tips, would you say the shafts are all the same length? Would you say they’re all centered?

Well, it turns out all three arrow shafts are the same length and start and end at the same point. Don’t believe it? Take a look at the bottom three arrows and start to embrace this idea of not always seeing things right.

We have an uncanny ability to perceive scenes over objects like we just saw in the Gestalt examples above and in some of our everyday scenarios. It’s even a big part of how we move and get around.

When someone is walking toward you, you know they aren’t growing taller. When they leave, you know they don’t just shrink into nothing. However, this natural system you’re equipped with doesn’t always prove to be the best. This image shows us why our built heuristics can’t always be relied on.

5. The Moon Illusion

The Moon Illusion

Credit: Wikipedia

The moon illusion is one that we can see every clear night, and shows us just how much the background of our focus changes our perception of the scene. This optical illusion causes the moon to look larger when it’s near the horizon compared to up in the sky with nothing around it but the black void of empty space and distant stars.

The explanation of this optical illusion seems to be the most debated, as it continues to perplex minds across the globe. Is it just that the size of the object depends on these background objects to portray its size, or does our brain take things up in the sky and associate them with being farther away and in-turn cause us to perceive the moon at different sizes throughout the night?

Books have been written on the topic and intellectual wars have been waged. Maybe one day it’ll all be put to rest, but until then, look up at the skyline and watch the moon as it dances around the planet throughout the night.

You’ll never be able to look at it the same.

About Eric

I am the founder, designer, coder, writer, and jack-of-all-trades here at PsychMob. Living in beautiful Colorado, I spend most of my spare time hiking, meditating, and altering my consciousness. I'm relentlessly in love with psychology and pull no punches when I write about it. I hope you enjoy the site as much as I do! Thanks for coming.

Categories:  Discrimination / Illusions / Neurons / Optics

1 Comment

One response to “Five optical illusions: How our eyes deceive us”

  1. Jenna Wilson says:

    Yes! Your memories can be so wrong… It’s strange that something we think is 100% true, can be 100% wrong. You see this in the criminal justice system all the time. So interesting!