5 Optical Illusions, and Why Your Brain Falls for Them

Our brains can do some pretty weird things to us sometimes. These prove it. 


The world is awash in stimuli. What gave our Stone Age ancestors an edge was not only the opposable thumb and walking upright, but our mind and our consciousness. For instance, our brain’s ability to filter out unimportant things in order to single out opportunities and threats. Consider that at any given moment our visual cortex is processing color, motion, orientation, and so much more. It’s a highly advanced system—but it isn’t perfect. It has certain biases. Enter cognitive illusions.

According to Gestalt psychology, our brain will often conjure symmetry where none exists. Although we often believe our perception is crystal clear, optical illusions quickly tune us into the fact that what the brain picks up and what reality is aren’t necessarily always the same. That’s also what gives us that eerie feeling of surprise. Some of us, myself included, are dazzled by mind-blowing optical illusions. They hint at deeper possibilities beneath the mundane.

The actual definition of an optical illusion is the “dissociation between the physical reality and the objective perception of an object/event.” By and large, most optical illusions are tricks that arrive due to how our vision works or how our brain processes visual information. As a result, there are a multitude of illusions that can play tricks on our brain, to make it think something’s going on when it really isn’t.

1. The Spinning Dancer

By Nobuyuki Kayahara - Procreo Flash Design Laboratory, Wikipedia Commons.

This one caught popular imagination and has spread like wildfire on the internet since 2003. Nobuyuki Kayahara is a web designer from Japan who came up with her. An urban legend quickly sprung up that it is a brain test. If she spins clockwise, it’s said, you’re right-brained, and if counterclockwise then it speaks to your left brain. But it’s false. The Spinning Dancer wasn’t designed by researchers with any particular neuroscience in mind.

Some people see her turning to the right, others to the left. This is an example of an ambiguous or reversible image. Since we don’t have any visual cues that add depth, our brain makes it up itself. The Necker Cube is probably the most common example of this. So she can spin either way, and if you look at her long enough, you may see her switch directions. The movement we see, which is obviously not there, is thought to be the result of tiny movements or vibrations in the eye.  

2. Einstein or Marilyn?

An illusion using real-world figures, by Aude Olivia. MIT 2007.

You might look at this picture and automatically see Einstein. But if you’re really far away from it and your eyesight is poor, you’ll see Ms. Monroe. If you are farsighted and you lift up your glasses, you may suddenly see the movie star hiding underneath the physicist. The reason is, Marilyn’s photo has far less detail. It has less pixels and portions of her are hiding in Einstein’s wrinkles and mustache. So the farther you move away from it, the more likely you’ll see the bombshell over the brain. Is your mind blown yet?

3. Moving Dots


A certain peculiarity with our eyes make the dots look as if they’re moving. It’s really an after-image which remains for a moment on our retinas just after we’ve seen it. Though scientists don’t know for sure, they believe minuscule, unfelt eye movements can cause a sort of overlap in what we see, thus giving certain patterns the illusion of movement. The colors are in high contrast to one another as well, which only increases the effect. Here's another stunningly simple dot illusion, made up of black dots and orange circles, known as the Ebbinghaus illusion. Did it fool you?

If you’re an illusion master, you can actually enter your own in theBest Illusions of the Year Contest.

The winning illusion producer takes home $3,000 and a prestigious award. The next two are some of last year’s finalists.

4. Silhouette Zoetrope

Zoetropes were pre-cinema toys popular in the 19th century which gave the user the impression that the image was moving. These pictures, separated by vertical lines, take advantage of what’s known as the phi phenomenon, which allows our brain to bridge the gap between still images, creating the illusion of motion.

5. Ambiguous Cylinder Illusion.

Engineering professor Dr. Kokichi Sugihara at Meji University in Japan, is the creator of this incredible illusion. It came in second place last year in the best illusions contest, but much more recently grew into a sensation on Reddit, Facebook and Twitter. I could explain it to you, but this video does a better job:

There are many different types of Illusions, and they all fill us with a sense of wonder, that momentary buzz of coming face-to-face with the bizarre. They’re also humbling, in a way, reminding us of our subjectivity and the limitations of our perceptions, and ability to see the true image. It’s only through intellectual rigor and scientific understanding that we can fully transcend them and by doing so, get a better sense of how our vision and brain works.

To see one more illusion, click here: 

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Yale scientists restore brain function to 32 clinically dead pigs

Researchers hope the technology will further our understanding of the brain, but lawmakers may not be ready for the ethical challenges.

Still from John Stephenson's 1999 rendition of Animal Farm.
Surprising Science
  • Researchers at the Yale School of Medicine successfully restored some functions to pig brains that had been dead for hours.
  • They hope the technology will advance our understanding of the brain, potentially developing new treatments for debilitating diseases and disorders.
  • The research raises many ethical questions and puts to the test our current understanding of death.

The image of an undead brain coming back to live again is the stuff of science fiction. Not just any science fiction, specifically B-grade sci fi. What instantly springs to mind is the black-and-white horrors of films like Fiend Without a Face. Bad acting. Plastic monstrosities. Visible strings. And a spinal cord that, for some reason, is also a tentacle?

But like any good science fiction, it's only a matter of time before some manner of it seeps into our reality. This week's Nature published the findings of researchers who managed to restore function to pigs' brains that were clinically dead. At least, what we once thought of as dead.

What's dead may never die, it seems

The researchers did not hail from House Greyjoy — "What is dead may never die" — but came largely from the Yale School of Medicine. They connected 32 pig brains to a system called BrainEx. BrainEx is an artificial perfusion system — that is, a system that takes over the functions normally regulated by the organ. The pigs had been killed four hours earlier at a U.S. Department of Agriculture slaughterhouse; their brains completely removed from the skulls.

BrainEx pumped an experiment solution into the brain that essentially mimic blood flow. It brought oxygen and nutrients to the tissues, giving brain cells the resources to begin many normal functions. The cells began consuming and metabolizing sugars. The brains' immune systems kicked in. Neuron samples could carry an electrical signal. Some brain cells even responded to drugs.

The researchers have managed to keep some brains alive for up to 36 hours, and currently do not know if BrainEx can have sustained the brains longer. "It is conceivable we are just preventing the inevitable, and the brain won't be able to recover," said Nenad Sestan, Yale neuroscientist and the lead researcher.

As a control, other brains received either a fake solution or no solution at all. None revived brain activity and deteriorated as normal.

The researchers hope the technology can enhance our ability to study the brain and its cellular functions. One of the main avenues of such studies would be brain disorders and diseases. This could point the way to developing new of treatments for the likes of brain injuries, Alzheimer's, Huntington's, and neurodegenerative conditions.

"This is an extraordinary and very promising breakthrough for neuroscience. It immediately offers a much better model for studying the human brain, which is extraordinarily important, given the vast amount of human suffering from diseases of the mind [and] brain," Nita Farahany, the bioethicists at the Duke University School of Law who wrote the study's commentary, told National Geographic.

An ethical gray matter

Before anyone gets an Island of Dr. Moreau vibe, it's worth noting that the brains did not approach neural activity anywhere near consciousness.

The BrainEx solution contained chemicals that prevented neurons from firing. To be extra cautious, the researchers also monitored the brains for any such activity and were prepared to administer an anesthetic should they have seen signs of consciousness.

Even so, the research signals a massive debate to come regarding medical ethics and our definition of death.

Most countries define death, clinically speaking, as the irreversible loss of brain or circulatory function. This definition was already at odds with some folk- and value-centric understandings, but where do we go if it becomes possible to reverse clinical death with artificial perfusion?

"This is wild," Jonathan Moreno, a bioethicist at the University of Pennsylvania, told the New York Times. "If ever there was an issue that merited big public deliberation on the ethics of science and medicine, this is one."

One possible consequence involves organ donations. Some European countries require emergency responders to use a process that preserves organs when they cannot resuscitate a person. They continue to pump blood throughout the body, but use a "thoracic aortic occlusion balloon" to prevent that blood from reaching the brain.

The system is already controversial because it raises concerns about what caused the patient's death. But what happens when brain death becomes readily reversible? Stuart Younger, a bioethicist at Case Western Reserve University, told Nature that if BrainEx were to become widely available, it could shrink the pool of eligible donors.

"There's a potential conflict here between the interests of potential donors — who might not even be donors — and people who are waiting for organs," he said.

It will be a while before such experiments go anywhere near human subjects. A more immediate ethical question relates to how such experiments harm animal subjects.

Ethical review boards evaluate research protocols and can reject any that causes undue pain, suffering, or distress. Since dead animals feel no pain, suffer no trauma, they are typically approved as subjects. But how do such boards make a judgement regarding the suffering of a "cellularly active" brain? The distress of a partially alive brain?

The dilemma is unprecedented.

Setting new boundaries

Another science fiction story that comes to mind when discussing this story is, of course, Frankenstein. As Farahany told National Geographic: "It is definitely has [sic] a good science-fiction element to it, and it is restoring cellular function where we previously thought impossible. But to have Frankenstein, you need some degree of consciousness, some 'there' there. [The researchers] did not recover any form of consciousness in this study, and it is still unclear if we ever could. But we are one step closer to that possibility."

She's right. The researchers undertook their research for the betterment of humanity, and we may one day reap some unimaginable medical benefits from it. The ethical questions, however, remain as unsettling as the stories they remind us of.

Scientists see 'rarest event ever recorded' in search for dark matter

The team caught a glimpse of a process that takes 18,000,000,000,000,000,000,000 years.

Image source: Pixabay
Surprising Science
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