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Chapter 8

Chapter 8. Perception. Our Perception. http://www.youtube.com/watch?v= IogEiKhEJFo. Yvaral. Sensation vs. Perception . Sensation involves receiving the stimulus Perception is the brain’s interpretation of the stimuli. Perception: Thresholds. Absolute Threshold –

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Chapter 8

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  1. Chapter 8 Perception

  2. Our Perception • http://www.youtube.com/watch?v=IogEiKhEJFo

  3. Yvaral

  4. Sensation vs. Perception • Sensation involves receiving the stimulus • Perception is the brain’s interpretation of the stimuli

  5. Perception: Thresholds • Absolute Threshold– • The smallest amount of stimulus we can detect (50% of the time) • Subliminal – • Stimulus below our absolute threshold • SOME COMPANIES CLAIM TO PRODUCE MESSAGE MEDIA THAT CAN CHANGE OUR UNWANTED BEHAVIOR…”LOOSE WEIGHT” • PSYCHOLOGICAL RESARCH DISPUTES THESE CLAIMS

  6. SUBLIMINAL MESSAGES • IF IT IS SUBLIMINAL, WE CAN’T PERCEIVE IT! • RESEARCH SUGGESTS IF CLAIMS “WORK” IT IS SIMPLE DUE TO PLACEBO EFFECT • http://www.youtube.com/watch?v=1QYYOuQGEp0 • IF IT IS TRULY “SUBLIMINAL” THEN WE WOULDN’T HEAR IT

  7. THRESHOLDS • Difference Thresholds - • Smallest amount of change needed in a stimulus before we can detect the change • WEBER’S LAW or “WEBER’S-FECHNER LAW” • States the change needed is proportional to the original intensity • The more intense the original stimulus, the more needed for us to notice a difference

  8. Weber’s Law Continued • Adding a dash of pepper to a plain dish you’ll notice • But adding a dash to an already spicy dish you won’t • Each Sense varies according to a constant, but constant are different per sense… • hearing 5% & vision 8% • Example: 8 candles would need to be added to 100 candles before it looked brighter

  9. Perceptual THEOries • These are NOT in competition with one another. Each Theory describes different examples or parts of perception. At times, it takes all the theories to explain our interpretation of our sensations • Signal Detection Theory – • Investigates the effects of distractions and interference we experience while perceiving the world • Tries to predict what we will perceive among competing stimuli

  10. Perceptual Theories: Signal Detection • Response criteria - • Determines how motivated we are to detect certain stimuli • Ex. Will the quarterback see the one open receiver in the end zone?

  11. Perceptual Theories: Signal Detection continued • False Positive – • When we think we perceive a stimulus that is present • Walking down the crowed hall and think you see a friend you wave, turns out you are waving to a stranger (real cool!)

  12. False Negative – • Not perceiving a stimulus when it is present

  13. Perceptual Constancies • Size Constancy: • Perceived size of an object remains constant, DESPITE changes in its retinal image size • As a car drives away we know it is not really shrinking! • Shape Constancy: • The perceived shape of an object unaffected by changes in its retinal image • As a door opens, we don’t think a magic spell morphed it onto a different shape

  14. Perceptual Constancies • Brightness Constancy: • Apparent brightness of an object stays the same under changing lighting conditions • As the sun sets and the usual red brick on your house appears a brown. We know that it is still red

  15. Fig. 7.1 Shape constancy. (a) When a door is open its image actually forms a trapezoid. Shape constancy is indicated by the fact that it is still perceived as a rectangle. (b) With great effort you may be able to see this design as a collection of flat shapes. However, if you maintain shape constancy the distorted squares strongly suggest the surface of a sphere. (From Spherescapes-1 by Scott Walter and Kevin McMahon, 1983.)

  16. What Constancy is this?

  17. Perceptual Terms • Empirical Perception: • A perception strongly influenced by prior experience • Visual Capture: • Where we perceive a conflict among senses, vision usually dominates • http://www.youtube.com/watch?v=G-lN8vWm3m0

  18. Figure-Ground Organization: Part of a stimulus stands out as a figure (object) against a plainer background (ground) *only the figure is seen* Reversible Figure: Figure and ground that can be reversed

  19. Fig. 7.2

  20. SO what is this? The first step in perceiving an image is determining the figure and ground.

  21. Max wertheimer & Wolfgang Kohler • Gestalt Principles shape our day to day perceptions

  22. Gestalt Principles of Organization – Max Wertheimer • Nearness: • Stimuli that are near each other tend to be grouped together • Similarity: • Stimuli that are similar in size, shape, color, or form tend to be grouped together • Continuation, or Continuity: • Perceptions tend toward simplicity and continuity • BOOK PAGE 206

  23. Gestalt Principles of Organization – Max Wertheimer • Closure: • Tendency to complete a figure so that it has a consistent overall form • Contiguity: • Nearness in time and space; perception that one thing has caused another • Common Region: • Stimuli that are found within a common area tend to be seen as a group

  24. Monocular Cues:, clues about distant based on use image of one eyeACCOMODATION – THE BENDING OF THE LENS THAT OCCURS WHEN THE EYE FOCUASES ON A NEARBY OBJECTSPICTORAL DEPTH CUES –creating DepthIN TWO-DIMENSIONAL SURFACES (PG 213)texture Changes Overlap light and shadow linear perspective Relative size height in the picture plane ARIELA PERSPECTIVE

  25. Let’s Read: Use Textbook • Depth Perception- THE ABILITY TO SEE 3 DIMENSIONAL SPACE AND JUDGE DISTANCE • Visual Cliff- SEE pg209 • Binocular Cues – clues about distance requiring use of two eyes Convergence – your eyes converge to see objects less than 50 feet away (muscle turn your eyes in) Retinal Disparity – seeing depth perception from the discrepancy between the right and left eye

  26. ames room - lopsided space that appears square when viewed from certain point

  27. Ponzo Illusion

  28. Müller-Lyer illusion

  29. Processing Principles • Top Down Processing - we form our perceptions starting with a larger object, concept, or idea before working our way toward more detailed information • Overview 1st, then notice smaller pieces / “Big Picture Processing” • Bottom –up Processing – "small chunk” processing and suggests that we attend to or perceive elements by starting with the smaller, more fine details of that element and then building upward until we have a solid representation of it in our minds. • Stimuli to concept • http://www.youtube.com/watch?v=TLHlfPTRekA

  30. Got it…? • For example, imagine that you are driving down an unfamiliar street and you see a sign for a convenience store. The sign has several missing letters, but you are still able to read it. Why? • you use __________ processing and rely on your existing knowledge to make an educated guess about what the sign says.

  31. What processing is this a Visual representation of?

  32. Part of Your Homework! • You need to research the internet or your book to find one example of each of the perceptual principles below. You either need a printed picture for each example or you could draw and replicate the image. Be sure to label each of your four examples. • Gestalt-Closure • Gestalt-Proximity • Gestalt-Continuity • Gestalt-Similarity • Size constancy • Shape constancy

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