1. ILLUSIONS Presented by: Ieva Zamaraitė

2. Menu: What is an illusion? What is an illusion? Illusion of length Illusion of length Illusion of shape Illusion of shape Illusion of size Illusion of size Illusion of touch Illusion of touch Illusion of temperature Illusion of temperature

3. What is an illusion? Illusion, a mistake in the perception of a sensory experience. An illusion occurs when what the brain perceives differs substantially from the actual qualities of an object or stimulus. Illusions may occur in any of the human senses, including vision, hearing, touch, smell, and taste. Illusion, a mistake in the perception of a sensory experience. An illusion occurs when what the brain perceives differs substantially from the actual qualities of an object or stimulus. Illusions may occur in any of the human senses, including vision, hearing, touch, smell, and taste.

4. However, errors in perception are only considered illusions if they are experienced by a large number of people. For example, if you are the only person who misreads a word, that is not an illusion. But if a large number of people misread the word in exactly the same way, then it may be considered an illusion. However, errors in perception are only considered illusions if they are experienced by a large number of people. For example, if you are the only person who misreads a word, that is not an illusion. But if a large number of people misread the word in exactly the same way, then it may be considered an illusion.

5. Illusion of length

6. The first illusion is probably the most famous and most studied illusion in psychology—the Müller-Lyer illusion, created by German psychiatrist Franz Müller-Lyer in 1889. The first illusion is probably the most famous and most studied illusion in psychology—the Müller-Lyer illusion, created by German psychiatrist Franz Müller-Lyer in 1889. The second illusion is called the Ponzo illusion, named after Italian psychologist Mario Ponzo. The second illusion is called the Ponzo illusion, named after Italian psychologist Mario Ponzo.

7. Explanation to Müller-Lyer illusion: Because we take distance into account when judging size, if two objects project the same image size on the retinas of our eyes, we interpret the object that seems farther away as larger. Explanation to Müller-Lyer illusion: Because we take distance into account when judging size, if two objects project the same image size on the retinas of our eyes, we interpret the object that seems farther away as larger.

8. The explanation for second illusion also involves depth perception. You interpret the oblique lines as indicating depth, which leads you to perceive the upper horizontal line as farther away than the bottom line. Although the images formed on your retinas by the two horizontal lines are actually equal in length, you perceive the upper line as longer because you think that it is farther away. The explanation for second illusion also involves depth perception. You interpret the oblique lines as indicating depth, which leads you to perceive the upper horizontal line as farther away than the bottom line. Although the images formed on your retinas by the two horizontal lines are actually equal in length, you perceive the upper line as longer because you think that it is farther away.

9. Illusion of shape

10. Look at the illustration entitled “Zöllner illusion.” In this example, a perfect square appears to be trapezoidal—that is, wider at the top than at the bottom—because of the background against which it is perceived. Why? Once again, the illusion arises because the oblique lines act as a cue to depth. Look at the illustration entitled “Zöllner illusion.” In this example, a perfect square appears to be trapezoidal—that is, wider at the top than at the bottom—because of the background against which it is perceived. Why? Once again, the illusion arises because the oblique lines act as a cue to depth.

11. Illusion of size

12. This unusual room is called the Ames room after American ophthalmologist Adelbert Ames, who first constructed such a room in the 1940s. This unusual room is called the Ames room after American ophthalmologist Adelbert Ames, who first constructed such a room in the 1940s.

13. The room itself is constructed in such a way that it provides misleading cues about distance. The left corner of the room is actually farther away from the viewer than the right corner of the room. In addition, the right side of the room is elevated so that the feet of both people appear at roughly the same relative height on the visual field. The room itself is constructed in such a way that it provides misleading cues about distance. The left corner of the room is actually farther away from the viewer than the right corner of the room. In addition, the right side of the room is elevated so that the feet of both people appear at roughly the same relative height on the visual field.

14. Illusion of touch Hold your right hand in front of you with all the fingers next to one another. With your eyes closed, run a pencil along the groove where the index and middle fingers meet. Note that you will perceive a single touch of the pencil. Now, cross your index finger over your middle finger. Once again, close your eyes and run the pencil between the two fingers. Now you should experience two separate touch perceptions. (by Aristotle) Hold your right hand in front of you with all the fingers next to one another. With your eyes closed, run a pencil along the groove where the index and middle fingers meet. Note that you will perceive a single touch of the pencil. Now, cross your index finger over your middle finger. Once again, close your eyes and run the pencil between the two fingers. Now you should experience two separate touch perceptions. (by Aristotle)

15. Presumably, this illusion arises because the touch receptors of the hand allow us to link the input from the right side of the index finger and the left side of the middle finger. However, when the fingers are crossed, we cannot link the input from the right side of the middle finger with the left side of the index finger. Thus, we perceive two separate touches. Presumably, this illusion arises because the touch receptors of the hand allow us to link the input from the right side of the index finger and the left side of the middle finger. However, when the fingers are crossed, we cannot link the input from the right side of the middle finger with the left side of the index finger. Thus, we perceive two separate touches.

16. Illusion of temperature A person puts one hand in a bowl of cold water and the other hand in a bowl of hot water, and allows both hands to adjust until the sensation of temperature disappears. A person puts one hand in a bowl of cold water and the other hand in a bowl of hot water, and allows both hands to adjust until the sensation of temperature disappears.

17. If the person then plunges both hands into lukewarm water, the hand that had adapted to the hot water feels cold in a lukewarm water, whereas the hand that had adapted to the cold water feels warm in the same water. This shows that the skin’s perception to temperature is relative, but not absolute. (by John Locke) If the person then plunges both hands into lukewarm water, the hand that had adapted to the hot water feels cold in a lukewarm water, whereas the hand that had adapted to the cold water feels warm in the same water. This shows that the skin’s perception to temperature is relative, but not absolute. (by John Locke)

18. Conclusion There still are disagreements on what exactly causes different illusions. There still are disagreements on what exactly causes different illusions. This field still needs researches. This field still needs researches. Explanation of illusions lead to understanding perception. Explanation of illusions lead to understanding perception.

19. References Contributed By: Hugh J. Foley Contributed By: Hugh J. Foley Microsoft ® Encarta ® Encyclopedia 2004. Microsoft ® Encarta ® Encyclopedia 2004.

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