Our Amazing Perception

I am currently watching a wonderful lecture series from The Teaching Company called “Understanding the Secrets of Human Perception”.  In lecture 18 “Illusions and Magic” Professor Vishton walks through a number of interesting perceptual illusions.

The first is the Café Wall Illusion:

All of the horizontal lines in this image are perfectly straight, but we infer a tilted edge because our brains decide that this is the best explanation for the distributions of brightness in the image.

The next perceptual oddity is motion-induced blindness.  Stare at the green dot in the center of the video and watch the green dots disappear:

The yellow dots are always displayed above the grid and are therefore projecting on your retina for the entire length of the video.  However, deep in your visual perception system the motion signals override the yellow dots.  Motion can often blind us to very large and salient things in the world around us, something which magicians often use to their advantage.

Fancy tiring out your color receptive cells?  How about a color adaptation after-effect illusion?  Once again you must stare at the dot in the center of the screen and watch in full-screen mode for the most dramatic results:

What’s happening here is your individual color-receptive cells become adapted and fatigued by staring at the color negative image.  This fatiguing of specific colors in your visual perception system produces brilliant real-life color when the image switches over to black and white.  As your previously fatigued color receptors regain their strength the second castle is exposed as a simple black and white image.

The final perceptual trick is the paper dragon illusion.  Mute the sound to avoid the annoying commentary:

Our perceptual system assumes that the nose of the dragon is closer to us than the body, but the opposite is true.  The paper dragon display is inside out.  The closest part of the paper dragon is the part that seems the farthest away and vice versa.  When the camera moves, the motion perception conflicts with the perception of the standard form of the dragon.  We perceive the dragon as moving because that is our mind’s best guess at what is actually happening.

Under the vast majority of circumstances our visual system delivers extremely accurate and reliable information to us.  In order to process the massive amount of sensory information in the world quickly and accurately, our sensory systems need to make inferential leaps.  This accurate and efficient data processing, with the rare illusion here and there, is the impressive evolutionary legacy of our sensory systems.  The next time you are waiting in line at the supermarket just consider the millions upon millions of years it took for our perceptual systems to attain this level of accuracy and complexity.  The time will fly by.

A word to the wise.  If you are going to buy this Secrets of Human Perception course, do not plan on having it playing on your iPad while driving your car on the way to work like I did.  You will be constantly distracted by the visual aids and examples, the most I’ve ever seen in any Teaching Company lecture series.  By the way, I am a self-confessed Teaching Company addict and I recommend their courses highly.  Always be sure to buy them on-sale; all of the lectures go on sale at least once a year.

Café Wall Image courtesy of illusionism.org

About SciAwakening

Blogging about religion, science, psychology, and whatever else is currently on my mind. http://ScientificAwakening.com

Posted on February 23, 2012, in Evolution, Perception, Psychology, Science and tagged , , , , , , , . Bookmark the permalink. 2 Comments.

  1. These are quite fascinating! And also interesting that presumably everyone’s perceptive abilities interpret them in the same way.

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