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  • 1. Sensation and PerceptionChapter 3

2. Sensation Sensation - the activation of receptors inthe various sense organs. Sensory receptors - specialized forms ofneurons. Sense organs: Eyes Visual Sensation Ears Auditory Sensation Nose- Olfactory Sensation Skin Tactile Sensation Taste buds (tongue) Gustatory Sensation 3. So where do vision and hearing (& the other senses) The Brain!happen? The physical energy inthe environment isdetected by the eyes,ears, etc. but we cantsee, hear, etc. until thebrain interprets themi.e., makes sense ofthem. So in a way, wesee, hear, smell, etc. inour brains! 4. Transduction Transformingsignals into neuralimpulses. Information goesfrom the senses tothe thalamus , then Remember Ethan in Sky High. Heto the various areas changes his body to slime. Solid form to liquid form. Change fromin the form of energy to another.Transduction is transforming physical energy into neural impulses 5. Sensory Thresholds Just noticeable differenceor the differencethreshold) - the smallestdifference between twostimuli that is detectable50 percent of the time. 6. Sensory Thresholds Absolute threshold - the smallestamount of energy needed for aperson to consciously detect astimulus 50 percent of the time itis present. 7. Subliminal Sensation Subliminal stimuli - stimuli that are belowthe level of conscious awareness. Just strong enough to activate the sensoryreceptors but not strong enough for peopleto be consciously aware of them. Limin - threshold Sublimin - below the threshold. Subliminal perception process by whysubliminal stimuli act upon theunconscious mind, influencing behavior. 8. Perception of Minimal Stimuli Subliminal Perception The concept of subliminal perception iswell known to the general public. Subliminal perception is the idea that a stimuluscan influence behavior even when it is so weakor brief that we do not perceive it consciously. There is concern that subliminal perception canpowerfully manipulate human behavior. 9. Perception of Minimal Stimuli What does subliminal mean? When the term subliminal is used, itrefers to the quality of being below the(sensory) threshold. Scientists use it to indicate that thestimulus was not consciously detected in agiven presentation. Because the only way to know if a stimulushas been detected is to ask, it is verydifficult to interpret the results of researchon subliminal stimuli. 10. Perception of Minimal Stimuli What subliminal perception cannotdo Claims that subliminal stimuli inadvertisements can make people buythings are unsupportable. This claim has been tested repeatedlyand no evidence has been found. Advertisements in American culturehave little need of subliminal stimuli.They are overtly and effectivelymanipulative. 11. Perception of Minimal Stimuli What subliminal perception cannot do Messages in music (recorded backwardsor superimposed) cannot make people doanything, evil or otherwise. This claim has also been repeatedly testedunder controlled conditions. No one listening to the messages can discernthese messages. No ones behavior has been changed afterlistening to music containing messages. 12. Perception of Minimal Stimuli What subliminal perception cannot do Subliminal audiotapes just dont work Claims that addictions can be overcome, self-esteem can be improved, and general self-improvement can be achieved through the useof subliminal audiotapes are also unsupported. Any results achieved through the use of thesetapes can be attributed to the placebo effect orto the individual users motivation to improve. 13. Perception of Minimal Stimuli What subliminal perception can do Some subtle effects on subsequentperception and emotion have beensupported Priming individuals to see an object insubsequent presentations has been achievedthrough repeated presentations (Bar &Biederman, 1998) Emotional states can be influenced bysubliminal presentation of messages that maybe perceived as emotionally loaded (Masling etal., 1991) 14. Perception of Minimal Stimuli Subliminal perception The fact that subliminal perception caninfluence behavior at all is interesting. But the effects overall are much smallerthan people hope or fear. 15. Habituation and Sensory Adaptation Habituation - tendency of the brainto stop attending to constant,unchanging information. Sensory adaptation - tendency ofsensory receptor cells to becomeless responsive to a stimulus that isunchanging. 16. Somesthetic Senses Somesthetic senses - the body sensesconsisting of the skin senses, the kinestheticsense, and the vestibular senses. Soma body Esthetic - feeling1. Skin senses - the sensations of touch,pressure, temperature, and pain. Sensory receptors in the skin Gate-control theory - pain signals must pass through agate located in the spinal cord. 17. Somesthetic Senses2. Kinestheticsense - sense of the locationof body parts in relation to the groundand each other. Proprioceptive receptors (proprioceptors)3. Vestibular senses - the sensations ofmovement, balance, and body position.Tells us where our body is oriented inspace. 18. Vestibular Sense Tells us where ourbody is oriented inspace. Our sense ofbalance. Located in oursemicircular canalsin our ears. 19. Kinesthetic Sense Tells us where ourbody parts are. Receptors locatedin our muscles andjoints. 20. Perception and Constancies Perception - the method by whichthe sensations experienced at anygiven moment are interpreted andorganized in some meaningfulfashion. Mental interpretation of sensationresults in perception 21. Perception and ConstanciesPERCEPTION = SENSATION +MEANINGFULINTERPRETATIONEx: Smell we experience due to theburning of an object is sensation andunderstanding that the burning object isrubber is PERCEPTION 22. Sensation and PerceptionSensation: your window to the worldPerception: interpreting what comesin your window. 23. Perception and Constancies Size constancy - the tendency to interpret anobject as always being the same actual size,regardless of its distance. Shape constancy - the tendency to interpretthe shape of an object as being constant,even when its shape changes on the retina. Brightness constancy the tendency toperceive the apparent brightness of an objectas the same even when the light conditionschange. 24. Shape constancy 25. Gestalt Principles Figureground - the tendency toperceive objects, or figures, asexisting on a background. Reversible figures - visual illusionsin which the figure and ground canbe reversed. 26. Do you seean old ladyor a younglady? 27. Do you see arabbit or aduck? 28. The white and black stripes onthese zebras can be reversed both can serve as either figure orground. 29. Some Laws of Perceptual OrganizationGestalt Principles Closure - the tendency tocomplete figures that areincomplete. Ex : While proof reading missing letters escape from our attention & our minds fill up the gap ! 30. Laws of Perceptual OrganizationGestalt Principles Continuity - the tendency toperceive things as simply aspossible with a continuous patternrather than with a complex, broken-up pattern.(Organizationofperception appears to be goinginfinitely in the same direction) Ex : Cinema scenes though not individually, when they run in a sequence at the rate of 15 frames per second, they appear to be one and continuous 31. Laws of Perceptual OrganizationGestalt Principles Pragnanz Pragnanz means compact butsignificant. In perceiving we do not add thedifferent sensations received and edit themso as to get at the meaningful interpretationof the object perceived. We always perceiveanything as a whole configuration or patternso that it is simple, meaningful and stable.Ex: On seeing a man riding a cycle, we do notperceive the cycle and the rider separately, it appearsas a whole unit to us. The mental act of organizingtakes place during perceptionMenu 32. Laws of Perceptual Organization Similarity - the tendency to perceivethings that look similar to eachother as being part of the samegroup. Proximity - the tendency toperceive objects that are close toeach other as part of the samegrouping.Menu 33. Menu 34. Depth Perception Depth perception - the ability toperceive the world in three dimensions. Studies of depth perception Visual cliff experimentMenu 35. Perceptual Illusions Illusions are wrong / mistakenperceptions Our perceptions are not alwaystrue and accurate. Sometimeserrors do creep in ourperception when our mindwrongly interpret the sensoryinput, which is otherwise knownas ILLUSION 36. Perceptual Illusions Illusion of movement : Ex: A spot oflight in dark appears to be movingaround Illusion of perceptive : Ex: Twoparallel lines appears to meet atalong distance 37. Perceptual Illusions Mller-Lyer illusion - illusion of line length thatis distorted by inward-turning or outward-turning corners on the ends of the lines,causing lines of equal length to appear to bedifferent. Moon illusion the moon on the horizonappears to be larger than the moon in thesky. Apparent distance hypothesis 38. Factors that Influence Perception Perceptual set (perceptual expectancy) - thetendency to perceive things a certain waybecause previous experiences orexpectations influence those perceptions. Top-down processing - the use of preexistingknowledge to organize individual features intoa unified whole. Bottom-up processing - the analysis of thesmaller features to build up to a completeperception. 39. Applying Psychology Extrasensory Perception (ESP) - claim ofperception that occurs without the use ofnormal sensory channels such as sight,hearing, touch, taste, or smell. Telepathy - claimed ability to read another persons thoughts, ormind reading. Clairvoyance - supposed ability to see things that are not actuallypresent. Precognition - supposed ability to know something in advance of itsoccurrence or to predict a future event. Parapsychology - the study of ESP, ghosts,and other subjects that do not normal