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Chapter 3: Sensation, Perception and Conscious Experience
Sensation: theprocess...
o Afterimage –sensory experience that occurs after a
visual stimulus has been removed.
o Ganglion –neurons that connect th...
Glaucoma Build up ofpressure
within theeyethatcan
lead to blindness
Diet and/or medication
Macular degeneration Degenerati...
4. The organ of Corti, on top ofthe basilar membrane, moves too.
Inside the organ of Corti, thousands of tiny receptor cel...
o SKIN SENSES - the senses of touch, pressure,
temperature, and pain.
o Gate-controltheory ofpain: thetheory that particul...
3. Closure –we areinclined tooverlook incompleteness in sensory
information and to perceive a whole object even where none...
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  1. 1. SOSC 2 GENERAL PSYCHOLOGY Chapter 3: Sensation, Perception and Conscious Experience PART 1 SENSATION Sensation: theprocess of receiving sensorydata from the environment and translating it to the brain. Perception: The sorting out, interpretation, analysis, and integration of stimuli by the sense organs and brain. Stimuli: Energy that produces a response in a sense organ. Psychophysics:thestudy ofthe relationship between the physical aspects of stimuli and our psychological experience ofthem. Receptorcell:a specialized cell that responds to a particular type ofenergy. Absolute threshold:theleast amount ofenergy that can be detected as a stimulation50percentof the time; the smallest intensity ofa stimulus that must be present for the stimulus to be detected. Noise: background stimulation that interferes with the perception ofother stimuli. The approximate absolute thresholds under ideal circumstances are as follows: Hearing The tick of a watch from 6 meters (20 feet). Vision A candleflameseen from 50 km (30miles) on a clear,dark night. Taste 1 gram (.0356 ounce) oftable salt in 500 liters (529 quarts) of water. Smell One drop of perfume diffused throughout a three-room apartment. Touch The wing of a bee falling on thecheek from a height of1 cm (0.39 inch) Differencethresholdor just-noticeabledifference(jnd): thesmallest change in stimulation that can be detected 50percentofthe time; the smallest level of added or reduced stimulation required to sense that a change in stimulation has occurred. Weber’s law: the principle that the jnd for any given sense is a constant fraction or proportion of the stimulation being judged. Adaptation: anadjustmentofthe senses tothelevelofstimulation they are receiving. THESENSES:  VISION A cross section of the human eye. Light enters the eye through the cornea, passes through the pupil, and is focused by the lens onto the retina. o The retina. A view ofthe retina through an ophthalmoscope, an instrument used to inspect blood vessels in the eye. The small dark spot is the fovea. The yellow circle marks the blind spot, where the optic nerve leaves the eye. o Cornea –the transparentprotective coating over the front part ofthe eye o Pupil –a smallopening inthe iris through which light enters the eye. o Iris –the colored partofthe eyethat regulates thesize ofthe pupil. o Lens –the transparent partoftheeyebehind the pupil that focuses light onto the retina. o Retina –thelining ofthe eye containing receptor cells that are sensitive to light. o Fovea –the area oftheretina that is the center ofthe visual field. o Rods –receptor cells in theretina responsiblefor night vision and perception ofbrightness. o Cones – receptor cells in the retina responsible for color vision. Rods and Cones. As you can see, the rods and cones are named for their shape. The basic cells oftheeye. Light enteringthe eye travels through the ganglion and bipolarcells andstrikes the light-sensitive rods and cones located at the back ofthe eye. The rods andcones thentransmit nerve impulses to the brain via the bipolar and ganglion cells. o Bipolar cells –neurons that have only one axon and one dendrite; inthe eye, these neurons connect the receptors on the retina to the ganglion cells. o Visual acuity –the ability to distinguish fine details visually. o Dark adaptation –increased sensitivity ofrods and cones in darkness. o Light adaptation –decreased sensitivity ofrods and cones in bright light.
  2. 2. o Afterimage –sensory experience that occurs after a visual stimulus has been removed. o Ganglion –neurons that connect the bipolar cells in the eyes to the brain. o Optic nerve –the bundle ofaxons ofganglion cells that carries neural messages from each eye to the brain. o Blind spot–the placeon theretina wheretheaxons of all the ganglioncells leavetheeye andwherethereare no receptors. o Optic chiasm – the point near the base ofthe brain where some fibers in the optic nerve from each eye cross to the other side ofthe brain. o Feature detectors –specialized brain cells that only respond toparticular elements in the visual field such as movement or lines ofspecific orientation. o Additive colormixing –the process ofmixing lights of different wavelengths to create new hues. o Trichromatic theory –the theory ofcolor vision that holds that all color perception derives from three different color receptors in the retina (usually red, green, and blue receptors). o Color blindness –partial ortotal inability to perceive hues. o Opponent-process theory–theory ofcolor vision that holds that three sets ofcolor receptors (yellow-blue, red-green, black-white) respond to determine the color you experience. Stare at the dot on this flag for about a minute and then look at a piece of plain white paper. What do you see? Most people see an afterimage that converts the colors in the figure into the traditional red, white, and blue U.S. flag. The electromagnetic spectrum. The eye is sensitive to only a very small segment ofthe spectrum, known as visible light. COMMON PROBLEMS OF VISION Condition Description Treatment Myopia (near- sightedness) Difficulty seeing objects ata distance Corrective lenses or corrective surgery Presbyopia (far- sightedness) Difficulty seeing close or highly detailed objects Corrective lenses or corrective surgery Astigmatism Blurred vision due to irregularities in the shape ofthelens or retina Corrective lenses or corrective surgery Cataract A thin cloudy covering develops on the surface oftheeye. Surgery to removethe cataract
  3. 3. Glaucoma Build up ofpressure within theeyethatcan lead to blindness Diet and/or medication Macular degeneration Degenerationofretinal cells, usually in and around thefovea; eventually causes blindness No treatmentat present Retinitis pigmentosa Hereditary disorder that involves deterioration ofcellsin the retina; eventually causes blindness No treatmentat present  HEARING o Sound: a psychologicalexperiencecreated by the brain in responseto changes in air pressure that arereceived by the auditory system. o Eardrum: thepart oftheearthat vibrates whensound waves hit it. o Sound waves: changes in pressure caused when molecules ofair or fluidcollide with one another and then move apart again. o Frequency: thenumber ofcycles per second ina wave; in sound, the primary determinant ofpitch. o Pitch: auditoryexperience corresponding primarily to frequency ofsound vibrations,resulting in a higher or lower tone. o Amplitude: the magnitude of a wave; in sound, the primary determinant ofloudness. Sound waves. As the tuning fork vibrates, it alternately compresses and expands the molecules of air, creating a sound wave. o Timbre: the quality or texture of sound; caused by overtones. o Oval window: membraneacross theopening between the middleearandinnerear thatconducts vibrations to the cochlea. o Cochlea: part ofthe inner earcontaining fluidthat can vibrate,whichin turn causes thebasilar membrane to vibrate. o Basilar membrane: membrane in the cochlea ofthe inner earthat responds tovibrations; itcontains sense receptors for sound. o Organ ofCorti: structureon thesurface ofthe basilar membrane that contains thereceptor cells for hearing. o Auditory nerve: the bundleofaxons thatcarries signals from each ear to the brain. Prolonged exposure to sounds above 85 decibels can cause permanent damage to ears, as can even brief exposure to sounds near the pain threshold. How we hear? 1. Sound waves enter the outer ear and travel to the eardrum, causing it to vibrate. 2. The vibrating eardrum causes the bones of the middle ear (the hammer, anvil, and stirrup) to strike each other, amplifying and carryingthe vibrations to the oval window and on to the fluid in the coiled cochlea ofthe inner ear. 3. Now, the moving fluid sets the basilar membrane, inside the cochlea, moving.
  4. 4. 4. The organ of Corti, on top ofthe basilar membrane, moves too. Inside the organ of Corti, thousands of tiny receptor cells are topped by a bundle ofhair-like fibers. As the basilar membrane vibrates, the fibers bend, stimulating the receptor cells to send a signal through the afferentnerve endings, which join to form the auditory nerve. 5. The auditory nerve carries impulses to the brain. 6. When the nerve impulses reach the temporal lobe, they are interpreted as sounds. At the top of each hair cell is a bundle offibers. Ifthe fibers bend as much as 100 trillionths of a meter, the receptor cells transmit a sensory message to the brain.  THEOTHER SENSES o SMELL (olfaction) The human olfactory system. The sense of smell is triggered when odor molecules inthe air reach the olfactory receptors located inside the top ofthe nose. Inhalingandexhalingodor molecules fromfood does muchto give food its flavorful “taste.” 1. As we breathe, molecules from theflowerreach thereceptor cells high in each nasal cavity. 2. The axons fromthese millions ofreceptors carry nerve impulses to the olfactory bulb. 3. The olfactory bulb transmits these impulses to thetemporallobes of the brain where they are experienced as smell. o Olfactory bulb: the small center in the brain. o Pheromones: chemicals thatcommunicateinformation to other organisms through smell. o TASTE (gustatory)  Taste buds: structures on the tongue that contain the receptor cells for taste. 1. Different areas on the tongue are slightly more sensitive to different tastes. 2. When we eat, chemicals in the food dissolve in saliva and come into contact withthe taste cells (receptors) within the taste buds. 3. Now, adjacent neurons fire,sending nerve impulses to the brain’s parietal lobe, where the messages are perceived as taste. There are 10,000taste buds on the tongue and other parts ofthe mouth. Taste buds wear out and are replaced every ten days.
  5. 5. o SKIN SENSES - the senses of touch, pressure, temperature, and pain. o Gate-controltheory ofpain: thetheory that particular nerve receptors inthespinal cord lead tospecific areas of the brain related to pain. Biopsychosocial theory: thetheory that the interaction of biological, psychological, and culturalfactors influences the intensity and durationofpain. PERCEPTION Perception: thebrain’s interpretationofsensory information so as to give it meaning. Gestalt laws of organization: a series ofprinciples that describe how we organize bits and pieces ofinformation into meaningful wholes. An illusory triangle.Whensensory informationis incomplete, we tend tocreate a complete perceptionby supplying the missingdetails. In this figure we will fillinthe lines thatlet us perceive a white triangle in the center ofthe pattern. Perceiving a pattern. Knowing beforehand that the block blotches in this figure represent a person riding a horse changes our perception ofit. An optical illusion. In the case of the trident we go beyondwhat is sensed (black lines on flat white paper) to perceive a three-dimensional object that isn’t really there. Figure-ground relationship. Doyou see a vase or the silhouettes ofa man and a woman? Both interpretations are possible, but not at the same time. Reversible figures like this work because it is unclearwhichpart ofthe stimulus is the figure and which is the neutral ground against which the figure is perceived. Although at first it is difficult to distinguish anything in this drawing, keep looking, and eventually you’ll probably be able to see the figure ofa dog. The dogrepresents a gestalt, or perceptual whole, which is something greater than the sum of the individual elements. Gestalt principles ofperceptual organizations 1. Proximity –Whenobjects are close to one another, we tend to perceive them together rather than separately. 2. Similarity–Objects that areofa similar color, size, or shape are usually perceived as part ofa pattern.
  6. 6. 3. Closure –we areinclined tooverlook incompleteness in sensory information and to perceive a whole object even where none really exists. 4. Continuity –items thatcontinuea pattern ordirection tend to be grouped together as part ofthe pattern.  PERCEPTUAL CONSTANCY: a tendency to perceive objects as stableand unchanging despite changes in sensory stimulation. o Shape constancy: the tendency to see an object the same shape no matter what angle it is viewed from. Shape constancy. Even though the image of the door on the retina changes greatly as the door opens, we stillperceive the door as being rectangular. o Size constancy: the perception of an object as the same size regardless ofthe distance from which it is viewed.  DEPTH PERCEPTION: The ability to view the world in three dimensions and to perceive distance. o Monocularcues: visual cues requiring the use ofone eye. o Binocular cues: visual cues requiring the use ofboth eyes. o Interposition: monocular distance cuein which oneobject, by partly blocking a second object, is perceived as being closer. Because the king of clubs appears to have been interposed on the king of spades, we perceive it to be closer to us. Because of the higher elevation and the suggestion of depth provided by the road, the tree on the right is perceived as being more distant and about the same size as the tree at lower left. Actually, it is appreciably smaller, as you cansee ifyou measure the heights of the two drawings. Railroad tracks that seem to join together in the distance are an example of linear perspective. o Perspective: monoculardistanceand depth cues that involve the convergence of lines, the haziness of images, and the relative elevation objects. o Texture gradient: monocular cueto distanceanddepth based on the fact that objects seen at greater distances appear to be smoother and less textured. o Shadowing: monocular cue to distance and depth based on the fact that shadows often appear ontheparts ofobjects that are more distant.  VISUAL ILLUSIONS: physical stimuli that consistently produce errors in perception. REFLECTION: 1. Do you think it is possibleto havesensationwithout perception? Is it possibleto haveperception withoutsensation? Explain why. 2. Describe the basic mechanisms involved in vision, hearing, and the other major senses. Reference: Feldman, R. S. (2010). Understanding Psychology. 9th Edition. McGraw Hill Companies, Inc. Morris, C.G.,et al. (2007). Psychology Concepts and Applications. Pearson Education, Inc. New Jersey. Prepared by: Mrs. Maria Angela L. Diopol Instructor