Perception and Reality Things Are Not Always As They Seem

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Perception and Reality Things Are Not Always As They Seem...

What is the World Like for Other People? Overview

  • Vantage Point
  • Line of Sight and Refraction Experiments
  • Color Blindness Tests
  • Rose-colored Glasses
  • Thought Experiment
  • Real-world Experiments
  • Blindsight and Neglect Patients
  • Homework Essay:
  • Thought Experiments

Vantage Point

  • This is probably very obvious but it is a very important limit upon our ability to perceive reality correctly:
  • Where you are relative to something else makes a difference.
  • For example, if you are looking down on a soft drink can it looks different than if we view it from the side.

Line of Sight

  • We can only see things that are not obstructed by something else.
  • We can determine if something is obstructed by drawing a straight line from our eyes to the object.
  • Whatever we can draw a straight line to without it hitting anything else is in our line of sight
  • This means that two people can have different perceptions of reality depending upon where they are seeing it from.


  • Fill out the handout as you conduct the refraction experiment.
  • Light Refraction Experiment
  • (1) Make experimental observations (e.g. drawings) of light refraction of a pencil in water from different angles.
  • (2) Think about additional methods of testing whether pencil is really bent.

Refraction Discussion

  • Did the pencil look the same or different when looking at it from different angles?
  • Which of these angles is correct (the way the pencil is really shaped)?
  • How can we test to see if the water really bends the pencil or if we are mistaken?

Dot Numbers: Do You See Any Numbers?

Dot Figures: Are any of these objects in the bigger picture? Which one(s)?

Perceptual Range

  • Normal humans can only see light that is in the visible light spectrum
  • This is very similar to only being able to hear sounds in the audible frequency range
  • (20 to 20,000Hz); some animals (like dogs) can hear high pitched sounds that we cannot
  • Some people have a disorder of their eyes called red-green color blindness so that red and green look the same to them. Their perceptual range is smaller than other people.

Rose-colored Glasses

  • What would it be like if we always had rose (red) colored glasses on?
  • What would Red look like to us? How about Blue? Think about it…
  • Now pick up the transparency in front of you and look at different colored objects through it.
  • Can you still tell a difference between the colors (red and blue, for example)?
  • How about the difference between red and grey?

Color Chart

Patients with Brain Injury

  • What is the difference between the pictures on the left
  • and the copies of them made on the right?

More Drawings by Spatial Neglect Patients

  • What is the difference between the drawings on the left and the copies of them made on the right?

Patient Asked to Cross Out All Lines

  • What is the pattern of lines being crossed out?

Neglect Discussion

  • How would you describe what is happening to these patients with brain injuries?
  • It is not that they can’t see things on the left at all:
  • If their eyes did not work all they would have to do is move the paper to the right and look at the side they could not see.
  • These patients are unaware that these pictures or objects have left sides (even though they have all seen these objects (clocks or flowers) normally before their accidents).


  • Conscious – The things that you are actively aware of in your mind (it is not the same thing as your conscience; which is your moral sense)
  • Subconscious – The things that are going on in your mind that you are not actively aware of (may or may not become aware of them later)
  • Unconscious – When you are in a condition when you are not aware of anything going on in the world or your mind


  • Is everything that is going on in a person’s mind conscious or are some things subconscious?
  • Is your perception of the world the same as everyone else’s even when observing the same thing or situation? Elaborate.
  • Does information coming to your sense organs (like your eyes) mean that the information becomes conscious to you?
  • What evidence do you have to support these conclusions?

Mysterious Case of Blindsight

  • A person has an injury to the parts of the brain that processes most (but not all) of the visual information from the eyes (but his eyes are fine).
  • When asked whether he can see anything, the person reports they are totally blind (cannot see anything).
  • When the person is told to guess what they were shown he/she does much better than pure chance.
  • How is this similar to Neglect patients?
  • Essay HW question:
  • What do these patients (Blindsight and Neglect) tell us about the role the brain plays in perception?

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