CHAPTER 6 SENSATION AND PERCEPTION LECTURE NOTES Chapter 6 Sensation and Perception Thresholds and Signal Detection o Absolute Sensory Threshold Intensity at which a given individual can detect a stimulus 50 of the time o Response Ways 2 ways to be correct Hit Correct Rejection 2 ways wrong False alarm misses o Signal Detection Theory The study of people s tendencies to make hits correct rejections misses and false alarms In signal detection experiments people s responses depend on their willingness to risk a miss or a false positive Experiment o Scenario 1 Light bulb dollar and penny o Scenario 2 Light bulb dollar penny and shock Subliminal Perception o The idea that a stimulus can influence our behavior even when it is presented so faintly or briefly or along with such distracters that we do not perceive it consciously o Myths Make you buy things Disney Movies The Little Mermaid The Rescuers Who Framed Roger Rabbit Aladdin The Lion King Myths Make you join a cult Rock Songs Barney Myths Subliminal audiotapes can help you improve your memory quit smoking and lose weight Truths Emotions and facial expressions Word Identification Recognition of Patterns Perceived Brightness o Depends on comparison to objects around it o Brightness Contrast The increase or decrease in an in an objects apparent brightness because of the effects of objects around it Feature Detection o Feature Detection Theory we begin recognition by breaking a complex stimulus into its component parts o Feature Detectors Neurons in the visual cortex that respond to the presence of certain simple features like lines and angles Gestalt Psychology o A field that focuses on our ability to perceive overall patterns German word that means Overall pattern or configuration Slogan was a whole is different from the sum of its parts o Visual perception is an active creation not just the adding of lines or dots Figure and Ground o In order to perceive things we must be able to separate figure and ground o We must be able to distinguish the from the o We usually take this process for granted except in situations when the task is difficult Reversible Figures o Stimuli that can be perceived in more than one way o In these cases we have to test hypotheses to make sense of what we see Gestalt Psychology o Proximity distance The tendency to perceive objects close to each other as forming a group o Similarity shapes Tendency to perceive objects that resemble ach other as forming a group o Continuation Occurs when the eye is compelled to move through one object an continue to other object o Closure Imagine the rest of the figure that is missing Closer and continuation can work best together when something has blocked the presumed object in the background Perception of Movement and Depth o Visual Constancy Tendency to perceive objects as keeping their shape size and color even though what actually strikes our retina changes from one moment to the next Perception of Movement o How do we distinguish between our own movements and that of other objects o We know the object remains stationary for 2 reasons We perceive motion through the object s background The vestibular system Perception of Motion o Induced or apparent movement When a background is moving and we incorrectly perceive as the object being in motion rather than the backgorund Stroboscopic movement o An illusion of movement created by rapid succession of stationary objects Phi Effect o Illusion of movement created when when two or more stationary light spearated by a short distance blink on and off at regular intevals Perception of Depth o Depth Perception Our perception of distances Retinal Disparity The discrepancy between the slightly different views the two eyes see becomes greater as the object comes closer We use the amount of discrepancy to gauge distance Convergence The degree to which the eyes turn in to focus on a close object o The closer the object the more your eyes turn in Binocular cues o Depend on both eyes Monocular cues o Enable a person to judge depth and distance with just one eye or when both eyes see the same image like a drawing o Depends on experience Monocular Cues o Object size a nearby produces a larger image than a distant one o Linear Perspective As parallel lines get further away they appear to get closer together o Detail we see closer objects in more detail o Interposition Closer objects tend to interrupt our view of more distant objects o Texture Gradient Distance btw evenly spaced items will appear to get shorter as distances increases Optical Illusions o Misinterpretation of a visual stimulus The relationship between size perception and depth perception helps us explain most optical illusions yet not all Relationship between size and depth o If we can identify an object s size we can also judge its distance Therefore if we misjudge distance we also tend to misjudge size o Ames Room