Blindsight: A Strange Neurological Condition That Could Help Us Explain Consciousness

Blindsight: A Strange Neurological Condition That Could Help Us Explain Consciousness Brain scan of a boy with fever and alteration of consciousness. Suttha Burawonk

Imagine being completely blind but still being able to see. Does that sound impossible? Well, it happens. A few years ago, a man (let’s call him Barry) suffered two strokes in quick succession. As a result, Barry was completely blind, and he walked with a stick.

One day, some psychologists placed Barry in a corridor full of obstacles like boxes and chairs. They took away his walking stick and told him to walk down the corridor. The result of this simple experiment would prove dramatic for our understanding of consciousness. Barry was able to navigate around the obstacles without tripping over a single one.

Barry has blindsight, an extremely rare condition that is as paradoxical as it sounds. People with blindsight consistently deny awareness of items in front of them, but they are capable of amazing feats, which demonstrate that, in some sense, they must be able to see them.

In another case, a man with blindsight (let’s call him Rick) was put in front of a screen and told to guess (from several options) what object was on the screen. Rick insisted that he didn’t know what was there and that he was just guessing, yet he was guessing with over 90% accuracy.

Into the brain

Blindsight results from damage to an area of the brain called the primary visual cortex. This is one of the areas, as you might have guessed, responsible for vision. Damage to primary visual cortex can result in blindness – sometimes total, sometimes partial.

So how does blindsight work? The eyes receive light and convert it into information that is then passed into the brain. This information then travels through a series of pathways through the brain to eventually end up at the primary visual cortex. For people with blindsight, this area is damaged and cannot properly process the information, so the information never makes it to conscious awareness. But the information is still processed by other areas of the visual system that are intact, enabling people with blindsight to carry out the kind of tasks that we see in the case of Barry and Rick.

Blindsight: A Strange Neurological Condition That Could Help Us Explain Consciousness Some blind people appear to be able to ‘see’. Akemaster/Shutterstock

 Get The Latest From InnerSelf

Blindsight serves as a particularly striking example of a general phenomenon, which is just how much goes on in the brain below the surface of consciousness. This applies just as much to people without blindsight as people with it. Studies have shown that naked pictures of attractive people can draw our attention, even when we are completely unaware of them. Other studies have demonstrated that we can correctly judge the colour of an object without any conscious awareness of it.

Blindsight debunked?

Blindsight has generated a lot of controversy. Some philosophers and psychologists have argued that people with blindsight might be conscious of what is in front of them after all, albeit in a vague and hard-to-describe way.

This suggestion presents a difficulty, because ascertaining whether someone is conscious of a particular thing is a complicated and highly delicate task. There is no “test” for consciousness. You can’t put a probe or a monitor next to someone’s head to test whether they are conscious of something – it’s a totally private experience.

We can, of course, ask them. But interpreting what people say about their own experiences can be a thorny task. Their reports sometimes seem to indicate that they have no consciousness at all of the objects in front of them (Rick once insisted that he did not believe that there really were any objects there). Other individuals with blindsight report feeling “visual pin-pricks” or “dark shadows” indicating the tantalising possibility that they did have some conscious awareness left over.

The boundaries of consciousness

So, what does blindsight tell us about consciousness? Exactly how you answer this question will heavily depend on which interpretation you accept. Do you think that those who have blindsight are in some sense conscious of what is out there or not?

Blindsight: A Strange Neurological Condition That Could Help Us Explain Consciousness The visual cortex. Geyer S, Weiss M, Reimann K, Lohmann G and Turner R/wikipedia, CC BY-SA

If they’re not, then blindsight provides an exciting tool that we can use to work out exactly what consciousness is for. By looking at what the brain can do without consciousness, we can try to work out which tasks ultimately require consciousness. From that, we may be able to work out what the evolutionary function of consciousness is, which is something that we are still relatively in the dark about.

On the other hand, if we could prove that people with blindsight are conscious of what is in front of them, this raises no less interesting and exciting questions about the limits of consciousness. What is their consciousness actually like? How does it differ from more familiar kinds of consciousness? And precisely where in the brain does consciousness begin and end? If they are conscious, despite damage to their visual cortex, what does that tell us about the role of this brain area in generating consciousness?

In my research, I am interested in the way that blindsight reveals the fuzzy boundaries at the edges of vision and consciousness. In cases like blindsight, it becomes increasingly unclear whether our normal concepts such as “perception”, “consciousness” and “seeing” are up to the task of adequately describing and explaining what is really going on. My goal is to develop more nuanced views of perception and consciousness that can help us understand their distinctly fuzzy edges.

To ultimately understand these cases, we will need to employ careful philosophical reflection on the concepts we use and the assumptions we make, just as much as we will need a thorough scientific investigation of the mechanics of the mind.The Conversation

About  The Author

Henry Taylor, Birmingham Fellow in Philosophy, University of Birmingham

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Recommended Books: Health

Fresh Fruit CleanseFresh Fruit Cleanse: Detox, Lose Weight and Restore Your Health with Nature's Most Delicious Foods [Paperback] by Leanne Hall.
Lose weight and feel vibrantly healthy while clearing your body of toxins. Fresh Fruit Cleanse offers everything you need for an easy and powerful detox, including day-by-day programs, mouth-watering recipes, and advice for transitioning off the cleanse.
Click here for more info and/or to order this book on Amazon.

Thrive FoodsThrive Foods: 200 Plant-Based Recipes for Peak Health [Paperback] by Brendan Brazier.
Building upon the stress-reducing, health-boosting nutritional philosophy introduced in his acclaimed vegan nutrition guide Thrive, professional Ironman triathlete Brendan Brazier now turns his attention to your dinner plate (breakfast bowl and lunch tray too).
Click here for more info and/or to order this book on Amazon.

Death by Medicine by Gary NullDeath by Medicine by Gary Null, Martin Feldman, Debora Rasio and Carolyn Dean
The medical environment has become a labyrinth of interlocking corporate, hospital, and governmental boards of directors, infiltrated by the drug companies. The most toxic substances are often approved first, while milder and more natural alternatives are ignored for financial reasons. It's death by medicine.
Click here for more info and/or to order this book on Amazon.


follow InnerSelf on


 Get The Latest By Email



The Day Of Reckoning Has Come For The GOP
by Robert Jennings,
The Republican party is no longer a pro-America political party. It is an illegitimate pseudo-political party full of radicals and reactionaries whose stated goal is to disrupt, destabilize, and…
Why Donald Trump Could Be History's Biggest Loser
by Robert Jennings,
Updated July 2, 20020 - This whole coronavirus pandemic is costing a fortune, maybe 2 or 3 or 4 fortunes, all of unknown size. Oh yeah, and, hundreds of thousands, maybe a million, of people will die…
Blue-Eyes vs Brown Eyes: How Racism is Taught
by Marie T. Russell, InnerSelf
In this 1992 Oprah Show episode, award-winning anti-racism activist and educator Jane Elliott taught the audience a tough lesson about racism by demonstrating just how easy it is to learn prejudice.
A Change Is Gonna Come...
by Marie T. Russell, InnerSelf
(May 30, 2020) As I watch the news on the events in Philadephia and other cities in the country, my heart aches for what is transpiring. I know that this is part of the greater change that is taking…
A Song Can Uplift the Heart and Soul
by Marie T. Russell, InnerSelf
I have several ways that I use to clear the darkness from my mind when I find it has crept in. One is gardening, or spending time in nature. The other is silence. Another way is reading. And one that…