Optical Illusions “An optical illusion is characterized by visually perceived images that, at least in common sense terms, are deceptive or misleading.” –Wikipedia.org Most people have seen an optical illusion at some point in their lives. Maybe it was a geometric shape that would be impossible to replicate in reality… maybe you’ve seen shapes appear to move as you stare at them on a sheet of paper... or maybe you’ve seen colors changing as you look around an image. There are tons of optical illusions out there; but have you ever wondered what makes them optical illusions? How do they work? How can you see something you know doesn’t exist?

Two Types Physiological Cognitive Physiological optical illusions are the kind that occur after staring at a bright light for a few seconds. The theory is that they result from an over-stimulation of certain neurological pathways in the brain. In other words, if you over-stimulate your vision by staring at a bright light and then close your eyes, you’ll “see” an afterimage of that light. Cognitive Cognitive optical illusions can be broken down into a few categories: Ambiguous: Cause a change in perception due to multiple interpretations. Distorting: Appear to distort an object’s size, length, curvature, color, etc. Paradox: Images/shapes that could not exist in reality (impossible objects). Fictional: Illusions that literally don’t exist (aka Hallucinations).

This is an example of a physiological optical illusion. The American Flag? Stare at the flag for thirty seconds, then quickly look at a blank wall or white piece of paper. What do you see? This is an example of a physiological optical illusion.

The Necker Cube Can you tell which orientation the wire frame cube is? This is an example of an ambiguous cognitive optical illusion.

What is this a picture of? Rubin Vase What is this a picture of? Faces or vases? This is an example of an ambiguous cognitive optical illusion.

Café Wall Illusion Are the horizontal lines straight and parallel, or curved? This is an example of a distorting cognitive optical illusion.

Mueller-Lyer Illusion Which line is the longest? Shortest? Hint: Get a ruler… check them out. This is an example of a distorting cognitive optical illusion.

Penrose Triangle Hey architecture majors, let’s see you make this: This is an example of a paradox cognitive optical illusion.

Penrose Stairs I’d love to see someone try to get to the top. This is an example of a paradox cognitive optical illusion.

This is an example of a physiological optical illusion. Who's That? Focus on the four dots for 45 seconds, then quickly look at a wall and blink. This is an example of a physiological optical illusion.

Checker Shadow Illusion Which square is darker? A or B? This one blows me away… they’re the same shade! This is an example of a distorting cognitive optical illusion.

Scintillating Grid Illusion Can you find the black circles? Hint: There are no black circles  This is an example of a distorting cognitive optical illusion.

Simultaneous Contrast Illusion In the middle bar, is the left or right side lighter? Yet again… blows me away. Try covering up the outer gradient and focus on the middle line. This is an example of a distorting cognitive optical illusion.

Look at the black dot as you move your head backward and foreward. Rotating Circles Look at the black dot as you move your head backward and foreward. Do you notice anything rotating? This is an example of a distorting cognitive optical illusion.

Want More? “Reality is merely an illusion, albeit a very persistent one.” –Albert Einstein

Research Time 40% of your project grade that is due Describing what type of illusion you made and why is it that Describing why your brain is seeing the illusion in a certain way – be sure to discuss light waves and reflection or refraction

Project 60% create your OWN ORIGINAL optical illusion 40% Lab Report Title Page Research Questions Describing what type of illusion you made and why is it that Describing why your brain is seeing the illusion in a certain way – be sure to discuss light waves and reflection or refraction