psyc chapter 5 notes
psyc chapter 5 notes PSYC100010
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This 0 page Class Notes was uploaded by Nicole Lee on Friday March 11, 2016. The Class Notes belongs to PSYC100010 at University of Delaware taught by Ly,Agnes Ruan in Fall 2015. Since its upload, it has received 43 views.
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Date Created: 03/11/16
PSYC chapter 5 Sensation and Perception 51 How Does Perception Emerge from Sensation sensation is detection of physical stimuli and transmission of that info to the brain no interpretation of what we are expecting perception is the brain s further processing organization and interpretation of sensory info our conscious experience to make the sensation useful and meaningful Two ways to interpret sensory information experience will guide sensation and perception bottomup processing is based on the physical features of the stimulus grapefruit s strong scent cool moisture and sharp taste topdown processing is how knowledge expectations or past experiences shape the interpretation of sensory information What s expected influences what s perceived sensory information is translated into meaningful signals sensory systems translate physical properties of stimuli into patterns of neural impulses sensory coding different environments are coded by activity in different neurons transduction is translating the stimuli into signals so the brain can interpret it To do so you need sensory receptors which are specialized cells in the sense organs that receive physical or chemical stimulation and pass the resulting impulses to the brain in the form of neural impulses Thalamus middle of the brain cerebral cortex interpret 5 senses Brain received qualitative that as most basic qualities of a stimulus like difference between sweet and salty different sounds instruments make coded by different sensory receptors responding to different stimuli quantitative has degreemagnitude of those qualities like how loud or soft the sound is or how sweet or salty it is Coded by the rate of a particular neuron39s firing each sense organ has different types of receptors designed to detect different types of stimuli detection requires a certain amount of the stimulus psychophysics is a subfield that examines psychological experiences of physical stimuli like how things are required for our sense organs to responddetect a stimulus observing the limits of sensory systems sensory thresholds sensory organs constantly acquire info from the environment absolute threshold is the minimum intensity of stimulation that must occur before you experience a sensation detect more often than by chance difference threshold is just noticeable difference so the smallest difference bt two stimuli that s noticed minimum amount of change required for a person to detect a difference So when you re reading and your sister is watching the TV you look up when the volume increased by a little and that s bc you noticed a difference in volume detecting a difference So threshold will increase as stimulus becomes more intense signal detection theory signal detection theory SDT detecting a stimulus is not an objective process but a subjective decision with sensitivity to the stimulus in the presence of other distraction and criteria used to make the judgement from ambiguous information During an experiment participants must state if they experience the stimulus and each participant judges whether an event occurs if the signal is present and the participant detects it it s a hit if the participants fails to detect the signal it s a miss if the participant detects while it s not present it s a false alarm and if the signal is there but the participants doesn t detect it it s a correct rejection response bias is a participant s tendency to report detecting the signal in an ambiguous trial influencing the result of whether heshe detected the signal sensory adaptation sensory adaption decrease in sensitivity to a constant level of stimulation due to a change in the environment that requires new responses At first the interpretation of the stimulus might be uncomfortable or unusual but with time those stimulus become expected and it s not as noticeable the brain constructs stable representations experience is a construction of your brain and resides inside your skull neurons inside the brain do not directly experience the outside world but through other neurons inside and outside the brain all happening in milliseconds What s perceived is different from the pattern of stimulation the eyes take in sensory receptors transduce stimuli into electrical impulses where the nerves then transmit those impulses to the brain then the brain creates a rich variety of perceptual experiences all sensory info is relayed to cortical and other areas of the brain from the thalamus then info from each sense is projected separately to a specific region of the cerebral cortex 52 How Are We Able to See sensory receptors in the eye transmit visual information to the brain seeing requires transducing energy light first passes the cornea eye s thick transparent layer that s more focused on the incoming light than the lens that s adjustable whereas cornea is not where light is bent farther inward and focused to form an image on the retina thin inner surface of the back of the eyeball and is the one part of the central nervous system that we can see pupil is the dark circle that is the small opening in the front of the lens it contacts closes and dilates opens and determines how much light is let in iris is a circular muscle that determine the eye s color and controls the pupil s size also changing the shape of the lens for it s flatten to focus on distant and thicken to focus on closer objects this process is called accommodation rods and cones two receptors rods respond at extremely low levels of light and responsible for night vision cones are responsible primarily for vision under brighter conditions and seeing color and details lightsensitive chemicals initiate the transduction of light waves into electrical neural impulses 120 million rods and 6 million cones Cones are located near the retina center called fovea becoming increasingly scarce near the outside edge transmission from the eye to the brain receptors that begins the generation of electrical signals are called photopigments which are protein molecules that become unstable and split apart when exposed to light this alters the membrane potential of the photoreceptors and triggers action potentials in downstream neurons light is transduced by the rods and cones other cells in the retina perform a series of sophisticated computations outputs from the cell converge on the retinal ganglion cells first neurons in the visual pathway with axons sending axons from inside the eye to the thalamus optic nerve axons in a bundle exiting in the eye area where the optic nerve leaves the retina is the blind spot optic chiasm is when half of the axons passes on info from the left side of the visual space is sent to the right hemisphere of the brain vice versa which then travels to the primary visual cortex impulses from the left visual field of each eye travel to the right side of the brain impulses from the right visual field from each eye travel to the left side of the brain what and Where pathways lower ventral stream is specialized for the perception and recognition of objects like determining their colors and shape upper dorsal stream is specialized for spatial perception determining where an object is and relating it to other objects in a scene Beyond the primary visual cortex these two parallel processing streams exist two separate streams of analysis of visual info bc it shows that damage to the ventral stream still allows spatial perception the color of light is determined by its wavelength visible light has electromagnetic waves that range from 400 to 700 nanometers and depending now the wavelengths that reach the eye it determines the color Trichromatic theory color vision results from activity in three different types of cones sensitive to the wavelengths short medium and long S M L bones respond maximally to it blindness doesn t mean you can t see all it s just missing certain cone receptors missing medium or long wavelengths would result in redgreen color blindness and missing a short would result in blueyellow color blindness happens about 8 of males and less than 1 for females opponentprocess theory alternative to the trichromatic theory red and green are opponent colors and blue and yellow are too occurs in the ganglion cells that make up the optic nerve carrying info to the brain L cones long wavelengths red M cones medium wavelengths green S cones short wavelengths blue hue saturation and brightness how color is categorized Hue distinctive characteristics that place a particular color in the spectrumcolor s greenness or oranageness depends on primarily on the light s dominant wavelengths when it reaches the eye saturation is purity of the colors varies according to the mixture of wavelengths in the stimulus like blue green red have only one wavelength whereas pastels has others mixture of many wavelengths so it s less pure brightness is based on color s perceived intensity determined chiefly by the total amount of light reaching the eye lightness is based on a visual stimulus by the brightness of the stimulus relative to its surroundings perceiving objects requires organization of visual information understanding how the brain uses such info from the senses to determine the sizes and distances of objects gestalt principles of perceptual organization gestalt shape form theorized that perception is more than the result of accumulating sensory data but more that the brain uses innate principles to organize sensory info into organized wholes helps to explain WHY we say or categorize things proximity closer to figures are to each other more likely we are to group and see them as part of the same object similarity group figures according to how closely they resemble each other in shape color orientation tend to cluster to consider a scene as a whole rather an individual parts continuity good continuation group together that have the same orientation completing an object hiding a portion of an object or in entire object from view closure complete figures that have gaps people see the figure as an oval rather than two separate curving lines illusory contours perceiving contours and cues to depth even when they do not exist figure and ground reversible figure illusion demonstrates what we perceive to be the object and what s the background cultural differences also play a part in determining which is which face perception better at recognizing members of their own race or ethnic group while others may claim that they all look alike depending on their exposure to people in the past not being able to recognize faces as well is called prosopagnosia but not objects what stream certain cortical regions and specific neurons specialize to perceive faces fusiform gyrus in the right hemisphere is specialized for perceiving faces depth perception is important for locating objects binocular depth cues from both eyes together and contribute to bottomup processing monocular depth cues are from each eye alone and provide organizational info for topdown processing binocular depth perception binocular disparity is caused by the distance bt humans eyes bc each eye has a different view of the world so when overlapped it compute distances to nearby objects ability to determine an object s depth based on that object s projections to each eye is stereoscopic vision binocular depth is convergence way the eye muscles turn the eyes inward when we view nearby objects being able to know how this info is used to perceive distance monocular depth perception can still tell the depth with one eye closed by of monocular depth cues pictorial depth cues occlusion near object occludes blocks an object that is far away relative size faroff objects project a smaller retinal image than close objects do if the far off and close objects are the same physical size familiar size knowing how large familiar objects are can tell how far away they are by the size of their retinal images linear perspective seemingly parallel lines appear to converge in the distance texture gradient as a uniformly textured surface recedes its texture continuously becomes denser position relative to horizon all else being equal objects below the horizon that appear higher in the visual field are perceived as being farther away objects above the horizon that appear lower in the visual field are perceived as being farther away size perception depends on distance farther away the object is smaller its retina image vice versa optical illusion arises when normal perceptual processes incorrectly represent the distance bt the viewer and the stimuli depth cues can fool us into seeing depth when it s not htere ames boxes ames boxes powerful depthsize illusions where one corner seems the same distance as the other but the object appears farther bc it projects a larger retinal image the ponzo illusion two lines look parallel so it seems that they are at different distances and have different sizes but they re actually the same size motion perception has internal and external cues we have neurons specialized for detecting movement fire when movement occurs has sensation but not perception detect external energy courses but not interpret them motion aftereffects when gazing at a moving image for a long time and then look at a stationary scene have a momentary impression that the new scene is moving in the opposite direction than the moving image you ve been staring at waterfall effect strong evidence that motionsensitive neurons exist in the brain bc directionspecific neurons begin to adapt to the motion becoming fatigued and therefore less sensitive stroboscopic motion perception made up of stillgrams images presented one after another to create the illusion of motion pictures object constancies help when perspective changes illusions occur when the brain creates inaccurate representations of stimuli in opposite situation object constancy the brain correctly perceives objects as constant despite sensory data that could lead it to think otherwise changing the angle distance or illumination does not change our perception of that object s size shape color or lightness but to keep these constancies need to understand the relationship bt the object and one other factor size constancy know how far away the object is from us shape constancy what angleangles we are seeing the object from color constancy compare the wavelengths of light reflected from the object with those reflected in the background lightness constancy how much light is being reflected from the object and its background 56 How Are We Able to Feel Touch and Pain touch haptic sense sensations of temp pressure and pain where our limbs are in space kinesthetic sense from receptors in muscles tendons and joints enabling us to pinpoint the positions in space and movements coordinate voluntary movements and invaluable in avoiding injury the skin contains sensory receptors for touch anything that touches the skin provides tactile stimulation that give rise to the experience of touch long axons enter the central nervous system by way of spinal or cranial nerves for temperature receptors for warmth and cold for pressure receptors are capsules in the skin that respond to vibration highslow pressure stretching and steady pressure touch info travels from thalamus to primary somatosensory cortex evoke the sensation of touch in different regions of the body in the parietal lobe there are two types of pain pain receptors exist throughout the body actual experience of pain is created by the brain just like other sensory experiences most pain result when damage to the skin activates haptic receptors where near fibers that convey pain info are thinner than those for temp and pressure fast fibers for sharp immediate pain slow fibers for chronic dull steady pain difference between the two fibers is the myelination or nonmyelination of their axons that travel up the spinal cord myelination speeds up neural communication so myelinated axons will send info quickly gate control theory pain experience depends on biological psychological and cultural factors and can be produced or suppressed gate control theory we experience pain when pain receptors are activated an a neural gate in the spinal cord allows the signals transmitted by smalldiameter nerve fibers that can be blocked at the spinal cord through to the brain controlling pain cognitive states like distraction worrying or focusing can close the gate for instance soldiers and athletes are concentrated on the gamebattle field that sometimes the injury that should have caused pain is inactive Hope positive moods and drugs slowing down the firing or neurons throughout the nervous system can also help lessen the dramatic sense of the painsituation CLASS NOTES Sensation what the body feels and absorbs Perception is the interpretation of those things feelings and absorptions one minute paper phantom limb is replacing a body part that is no longer there It acts as a substitution but lacks the sensation that a biological limb had Therefore the perception is also changed in that it does not have sensory nerves to send signals to the gate spinal cord to the brain for the brain to interpret what is happening to the body Sensation v Perception taste smell touch hearing vision how mental state influences the experience of pain Gate Control Theory allowing signals to go past or blocked from reaching the brain to have perception of the sensation Placebo Effect believing that it s real but it s actually not affecting the results or response from the participants bottomup processing taking the information from sensory putting bits and pieces together into a whole picture making it a higher level of meaning topdown processing thoughts cognition breaking it down to understand the meaning of the small bits of pieces How the small sensory are experienced both processing are happening ALL THE TIME but l3 looks like a B looks like the number 13 maybe the number 8 may be A B C may be 12 13 14 piecing together small parts to general what it is so it s more of bottomup processing Michael Shermer
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