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Slide 2 HOW MANY FACES DO YOU SEE? Slide 3 13 Slide 4 CHAPTER 8 Perception Slide 5 Yvaral Slide 6 SENSATION VS. PERCEPTION Sensation involves receiving the stimulus Perception is the brains interpretation of the stimuli Slide 7 PERCEPTION: THRESHOLDS Absolute Threshold The smallest amount of stimulus we can detect (50% of the time) 1 gram table salt in 500 liters of water 1 drop of perfume diffused throughout a 3 bedroom apartment Subliminal Stimulus below our absolute threshold SOME COMPANIES CLAIM TO PRODUCE MESSAGE MEDIA THAT CAN CHANGE OUR UNWANTED BEHAVIORLOOSE WEIGHT PSYCHOLOGICAL RESARCH DISPUTES THESE CLAIMS Slide 8 SUBLIMINAL MESSAGES IF IT IS SUBLIMINAL, WE CANT PERCEIVE IT! RESEARCH SUGGESTS IF CLAIMS WORK IT IS SIMPLE DUE TO PLACEBO EFFECT http://www.youtube.com/watch?v=1QYYOuQGEp0 http://www.youtube.com/watch?v=1QYYOuQGEp0 IF IT IS TRULY SUBLIMINAL THEN WE WOULDNT HEAR IT Slide 9 THRESHOLDS Difference Thresholds - Smallest amount of change needed in a stimulus before we can detect the change Slide 10 JUST NOTICEABLE DIFFERENCE OR JND The just noticeable difference (JND), also known as the difference threshold, is the minimum level of stimulation that a person can detect 50-percent of the time. Slide 11 WEBER-FECHNER LAW WEBERS LAW or WEBERS-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 Girl is wearing a lot of perfume, it will take _________ to notice an increase. Your eating plain rice, it will take __________to notice an increase. Slide 12 WEBERS LAW CONTINUED Adding a dash of pepper to a plain dish youll notice But adding a dash to an already spicy dish you wont 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 Slide 13 TIME FOR JUST NOTICEABLE DOUGHNUTS Volunteer, anyone? Slide 14 PERCEPTUAL THEORIES These are NOT in competition with one another. 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 What makes this different from traditional threshold theories is that the subject makes a decision, a cognitive act, as to whether the signal is present or not and what signal to pay attention to or not Slide 15 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? Slide 16 PERCEPTUAL THEORIES: SIGNAL DETECTION CONTINUED False Positive We perceive a stimulus that isnt present Walking down the crowed hall and think you see a friend you wave, turns out you are waving to a stranger (real cool!) Slide 17 IS THAT A FALSE + OR FALSE ? False Negative Not perceiving a stimulus when it is present Slide 18 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 dont think a magic spell morphed it onto a different shape Slide 19 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 Slide 20 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.) Slide 21 Slide 22 WHAT CONSTANCY IS THIS? Slide 23 PERCEPTUAL TERMS Empirical Perception: A perception strongly influenced by prior experience Common explanation for false positives Visual Capture: Where we perceive a conflict among senses, vision usually dominates = McGurk Effect http://www.youtube.com/watch?v=G-lN8vWm3m0 Slide 24 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 Slide 25 FIG. 7.2 Slide 26 Slide 27 Slide 28 Slide 29 Slide 30 SO WHAT IS THIS? The first step in perceiving an image is determining the figure and ground. Slide 31 Slide 32 MAX WERTHEIMER & WOLFGANG KOHLER Gestalt Principles shape our day to day perceptions Slide 33 GESTALT PRINCIPLES OF ORGANIZATION MAX WERTHEIMER Summarize them in your notes as we view them, you need to know them for the test http://psychology.about.com/od/sensationandper ception/ss/gestaltlaws_2.htm http://psychology.about.com/od/sensationandper ception/ss/gestaltlaws_2.htm Slide 34 Monocular cues vs. Binocular cues Slide 35 MONOCULAR CUES- CLUES ABOUT DISTANT BASED ON USE IMAGE OF ONE EYE ACCOMODATION - THE BENDING OF THE LENS THAT OCCURS WHEN THE EYE FOCUASES ON A NEARBY OBJECTS PICTORAL DEPTH CUES CREATING DEPTH IN TWO-DIMENSIONAL SURFACES (PG 213) TEXTURE CHANGES OVERLAP LIGHT AND SHADOW LINEAR PERSPECTIVE RELATIVE SIZE HEIGHT IN THE PICTURE PLANE ARIELA PERSPECTIVE Slide 36 BINOCULAR CUES Depth Perception- THE ABILITY TO SEE 3 DIMENSIONAL SPACE AND JUDGE DISTANCE Visual Cliff Apparatus- (Gibson & Walk) SEE pg 209 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 Slide 37 AMES ROOM - LOPSIDED SPACE THAT APPEARS SQUARE WHEN VIEWED FROM CERTAIN POINT Slide 38 Slide 39 PONZO ILLUSION Slide 40 MLLER-LYER ILLUSION Slide 41 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 1 st, 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 http://www.youtube.com/watch?v=TLHlfPTRekA Slide 42 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. Slide 43 WHAT PROCESSING IS THIS A VISUAL REPRESENTATION OF? Slide 44 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 6 examples. Gestalt-Closure Gestalt-Proximity Gestalt-Continuity Gestalt-Similarity _______________ Size constancy Shape constancy