By Miguel Cortinas and Ryan Longo

Optical Illusions

Main Objective

• Explain the idea of optical illusions and their cause.

Introduction to Optical Illusions• Optical Illusion- (visual illusion) caused by visually

perceived images that differ from reality.

• The information gathered by the eye is processed in the brain to give a perception that does not match up with the physical measurement of the stimulus source.

• Three main types: Literal, Physiological, and Cognitive.

Literal Illusions• Literal optical illusions are

images that differ from the objects that create them.

• Artists may use objects such as fruit or foliage to create a portraiture or scenery.

Physiological Illusions• Physiological illusions are

the effects on the eyes and brain of excessive stimulation of a specific type.

• Artists may use color or movement to confuse the viewers' eyes and brains.

Cognitive Illusions• Cognitive illusions are

where the eye and brain make unconscious inferences.

• They can also be known as "mind games".

• Perspective and color heavily influence this genre.

Idea of Optical Illusions• When we witness an illusion, we perceive something that

does not correspond to what is actually out there—what exists in the real world.

• Illusions fool us! They convince us of things that are not true.

• Dictionary definitions of illusion usually state that an illusion is a sensory perception that causes a false or distorted impression, or a misrepresentation of a "real" sensory stimulus.

Don’t Believe Your Eyes• Illusions are misperceptions that are perceived by most

people, and are based on a specific stimulus received under certain conditions.

• Some experiments with animals indicate that several species of mammals and birds are "fooled" by illusions in much the same way we are.

• Illusions are different from both hallucinations and delusions.

Illusions

• Illusion is a kind of wrong perception.

• In illusion, an external stimulus is always present. In other words, illusions are caused by external stimulations.

• Illusion is almost universal.

• The same situation arouses the same type of illusion in most people.

Hallucinations• Hallucination is a false perception.

• In hallucinations, no external stimulus is present. Hallucinations are caused by internal stimulations.

• A hallucination is seeing, hearing, tasting, smelling or feeling things that do not really exist.

• Certain drugs can cause hallucinations. Certain mental illnesses can also cause hallucinations. People who have hallucinations are not necessarily ill, lack of sleep can also cause hallucinations.

• People who have hallucinations are not necessarily ill, lack of sleep can also cause hallucinations. Hallucinations just before going to sleep or just after waking up are considered normal.

ExamplesThis just looks like a normal triangle right? But where does it end?

At first look this cube looks fine, but look at the center stem.

Is It A Rabbit or A Duck??

Evaluation Questions1. What is an optical illusion?

2. What are the causes of optical illusions?

3. What are the 3 types of illusions?

4. How do optical illusions differ from hallucinations and delusions?

Any Questions??

Bibliography• Block, J. (n.d.). What is an Illusion?.sandlotscience.com

. Retrieved October 29, 2013, from http://www.sandlotscience.com/EyeonIllusions/whatisanillusion.htm

• Nierenberg, C. (n.d.). Optical Illusions: When Your Brain Can't Believe Your Eyes. ABC News. Retrieved October 29, 2013, from http://abcnews.go.com/Health/EyeHealth/optical-illusions-eye-brain-agree/story?id=8455573

• Nin, A. (n.d.). Causes of Optical Illusions.buzzle.com. Retrieved October 29, 2013, from http://www.buzzle.com/articles/causes-of-optical-illusions.html