Illusions

These are some tricks and illusions from around the web that reveal fascinating facets of our thought processes:

1. The Checker-Shadow Illusion — An interactive color perception demonstration that will have you shaking your head in disbelief (or you get your money back).
2. Sensory Homonculus Picture — A couple of pictures showing what a man’s body would look like if each body part was in proportion to the area of the cortex correlated with sensory perception of that body part.
3. A Blindspot Demonstration — This page will walk you through a couple of steps to show that you have a pretty big blindspot, but your brain fills in the information using your other eye and extrapolating the rest. Remember to close one eye!
4. A Ball in a Box — This movie shows how our brain forms 3D models of a scene. We assume that a moving shadow is the result of a moving object instead of a moving light source, both because it is more likely and evolutionary may have been more dangerous.
5. Iterated Choices — A Prisoner’s Dilemma game with repeated play between you and an artificial intelligence that reacts to your decision. Your goal is to achieve the maximum possible reward. Those who have read about altruism in evolutionary psychology will quickly realize the dominant strategy, but it is fun to test these results yourself.
6. The Max Plank Institute for Biological Cybernetics — There are 3 cool visual illusions here that reveal some facets about how we perceive the world, all of which are recommended.
7. The Motion Aftereffect Illusion — Your brain adjusts to the motion, and when it stops your perception cells are still firing to adjust against it, so you will see motion in the opposite direction. There is evidence that this effect takes place not in the retina, but further downstream (and thus due to central processing).
8. The Phi Phenomenon — The basis for motion pictures, this phenomenon also provides a window into our cognition. If we see a number of static images, our brains automatically combine them into one moving image. This phenomenon is especially effective if the moving images would make sense in the real world. So a baseball moving horizontally would make sense, while a piano with such motion might not.
9. The Common Fate Phenomenon — A stunning example of how we form 3-D images from 2-D ones. Instead of seeing a group of random dots, we see a shape in motion–although as you will see, the direction of that motion can be ambiguous.
10. A Double Face — This is a good picture of a “double face”, which looks very odd. But why is it so hard to look at? Perhaps because the features on the face are competing with one another for attention. Since recognizing human faces is so innate, this would be a difficult effect for our executive system to override.
11. The Troxler Effect — If you stare at the center dot for long enough (and I mean stare), then the outer ring will fade at least partially away in bursts. Woah.

And here are some links to other websites with online experiments that you can participate in:

The Cognition and Language Lab — Some online experiments involving language and visual memory, among other topics.

Psychological Research on the Net — A “meta” list, with a section for studies added in the last 30 days.

Web-based Experiments, Wikipedia — Wikipedia’s page for online experiments, which includes links to specific experiments.