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Chapter 5-8

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Psychology 1000

Chapter 5 Reading Notes 10/26/2011 6:36:00 AM  Synesthesia: ‘mixing of the senses’  may experience sound as colors or tastes and touch sensations o Women more likely to be synaesthetes than men  Sensory receptors must translate stimuli information into nerve impulses for body to understand  process of transduction  Special neurons called feature detectors break down and analyze specific features of stimuli  Binding problem: how do we bind all of our perceptions into one complete whole while keeping its sensory elements separate?  Sensation: stimulus-detecting process by which our sense organs respond to and translate environmental stimuli into nerve impulses that are sent to brain  Perception: making ‘sense’ of what our senses tell us  active process od organizing stimulus input and giving it meaning  Transduction: process whereby characteristics of a stimulus are converted into nerve impulses  Psychophysics: studies relation between physical characteristics of stimuli and sensory capabilities o Absolute limit of sensitivity (ex: what’s the softest sound or weakest salt solution tat humans can detect?) o Differences between stimuli (ex: what is the smallest difference in brightness we can detect?)   Stimuli Detection: The Absolute Threshold  Absolute threshold: lowest intensity at which a stimulus can be detected correctly 50% of the time o The lower the absolute threshold, the greater the sensitivity o No fixed absolute threshold, instead there is a range o Decision criterion: a standard of how certain a person must be that a stimulus is present before they can say they detect it  Can change depending on fatigue, expectation and potential significance of stimulus o Signal Detection Theory: concerned with factors that influence sensory judgments  The Difference Threshold  Difference Threshold: the small difference between two stimuli that people can perceive 50% of the time  also called JND (just noticeable difference)  Weber’s Law: the difference threshold, or JND, directly proportional to the magnitude of the stimulus with which the comparison is being made o Can be expressed as a Weber fraction  the smaller the fraction, the greater the sensitivity  Sensory Adaptation: sensory neurons engineered to respond to a constant stimulus by decreasing their activity, this diminishing of sensitivity referred to as sensory adaptation/habituation Sensory Systems  Vision  Cornea: a transparent protective structure at front of the eye, light waves enter the eye through this  Pupil: adjustable opening that can dilate or constrict to control amount of light that enters the eye o Pupil’s size controlled by muscles in the iris which surrounds pupil  Lens: elastic structure that becomes thinner to focus on distant objects and thicker to focus on nearby objects  Retina: multi-layered tissue at rear of fluid-filled eyeball o Myopia (nearsightedness)  lens focuses on visual image in front of retina, resulting in blurred images for faraway objects  Can occur because eyeball is longer than normal o Hyperopia (farsightedness)  lens doesn’t thicken enough so image focused on point behind retina  Aging process causes eyes to become shorter, resulting in hyperopia and older people needing reading glasses  Retina is actually extension of brain, contains 2 types of light-sensitive receptors o Rods: primarily black and white brightness receptors (function best in dimlight)  500 times more sensitive to light than are cones o Cones: color receptors, function best in bright illumination o Fovea: small area in centre of retina that contains only cones  Bipolar Cells: have synaptic connections with roads and cones o Bipolar cells synapse with layer of ganglion cells, whose axons are collected into a bundle to form optic nerve  visual acuity: ability to see fine detail o greatest when visual image projects directly onto fovea  Photopigments: rods and cones translate light waves into nerve impulses through action of protein molecules  Dark Adaptation: progressive improvement in brightness sensitivity that occurs over time under conditions of low illumination o After absorbing light, photoreceptor is depleted of its pigment molecules for a period of time o During process of dark adaptation, photopigment molecules are regenerated and receptor’s sensitivity increases  Trichromatic Theory: three types of color receptors in retina o Though all cones can be stimulated by most wavelengths, individual cones most sensitive to wavelengths corresponding to red, green or blue o If all three cones equally activated, pure white color is perceived  Problems with trichromatic theory o Yellow isn’t produced from red and green  red-green colorblind people can still see yellow o Afterimage: image of different color appears after color stimulus has been viewed steadily and then withdrawn  Opponent-Process Theory: each of three wavelengths responds to two different wavelengths o Red or green, blue or yellow, black or white  Dual-Process Theory o Combines trichromatic and opponent-process theories for color transduction process o Certain ganglion cells in retina respond in opponent-process fashion by altering their rate of firing  Trichromat: person sensitive to all three color systems  Dichromat: person who is color blind in on of the systems (red-green or blue-yellow)  Monochromat: person only sensitive to black-white system Process of Combining Messages from Photoreceptors to Perception of Visual Scene  From retina, optic nerve sends impluses to visual relay station in thalamus  From thalamus, input routed to various parts of cortex, especially primary visual cortex (in occipital lobe)  Feature detectors: groups of neurons within primary visual cortex organized to receive and integrate nerve impulses from retina o Fire selectively in response to stimuli that have specific characteristics  From primary visual cortex, input goes to visual association cortex where we ‘recognize what it is’ Audition  Sound is actually pressure waves in air, water, or some other conducting medium  Frequency: number of sound waves, or cycles, per second o Hertz (Hz): technical measure of cycles per second  higher frequency = higher perceived pitch  Amplitude: vertical size of the soundwaves (amount of compression and expansion of molecules in conducting medium)  measures perceived loudness o Decibels (db): measure of psychical pressure that occurs at eardrum  Sound waves travel to auditory canal leading to eardrum (movable membrane that vibrates in response to soundwaves)  Beyond eardrum is middle ear (cavity housing 3 tiniest bones) o Hammer (malleus) o Anvil (incus) o Stirrup (stapes) o Vibrating activity of these bones amplifies soundwaves more than 30 times  Cochlea: in inner ear; coiled snail-shaped tube filled with fluid and contains basilar membrane  Basilar membrane: sheet of tissue that runs length of cochlea  Organ of Corti: on basilar membrane; contains 16000 tiny hair cells which are sound receptors o Hair cells synapse with neurons of auditory nerve, which then sends impulses in thalamus to auditory cortex (temporal lobe)  Soundwave strikes eardrum  pressure created by 3 bones sets fluid inside cochlea into motion o Fluid waves cause bending of hair cells in organ of corti o Bending of hair cells triggers release of neurotransmitter substance Coding of Pitch and Loudness  Loudness  high-amplitude sound waves cause hair cells to bend more o Higher rate of neuron firing within auditory nerve o Some neurons have higher thresholds so fire only when intense sound o Loudness coded in terms of…  rate of firing in axons of auditory nerve  which specific hair cells are sending messages  Pitch  one coding process for frequencies below 1000 Hz and another one for above  Frequency Theory: nerve impulses sent to brain match frequency of sound waves o 30 Hz sound wave = sends 30 volleys of nerve impulses per second to brain o Major flaw: neurons limited in their rate of firing so cannot produce high enough frequencies of firing to match wave frequencies above 1000 Hz  George von Bekesy  Place theory: specific point on cochlea where fluid waves peak and most strongly bend hair cells serves as frequency coding cue o Tonal frequency ‘map’ that corresponds to specific areas of cochlea o High frequency sounds  abrupt wave that peaked close to oval window o Low frequency sounds  slower fluid wave that peaks further down cochlear canal Sound Localization and Hearing Loss  Nervous system uses info concerning time and intensity differences of sounds arriving in both ears to locate source of sounds in space  Sounds arrives first & loudest in ear closest to the sound  Sound directly in front of us  sound waves reach both ears at same time  Conduction deafness: caused by problems in mechanical system that transmits sound waves to cochlea o Ex: punctures eardrum, loss of function in tiny bones of middle ear o Can use a hearing aid  Nerve Deafness: caused by damaged receptors within inner ear or damage to auditory nerve o Hearing aid won’t help o Caused by aging, disease, exposure to loud sounds Gustation (taste) and olfaction (smell) are chemical senses  respond to chemical molecules rather than energy  Sense of taste responds to 4 qualities  sweet, sour, salty and bitter  Taste buds: chemical receptors concentrated along edges and back surface of tongue  Receptors for smell are long cells that project through lining of upper part of nasal cavity and into mucous membrane  Olfactory bulb: forebrain structure above nasal cavity; olfactory receptors that fire send their input here  Pheromones: chemical signals found in natural body scents Tactile Senses  Touch  sensitivity to extreme temperatures and pain, allows us to have orgasms, etc  4 tactile sensations o pressure (touch) o pain o warmth o cold  primary receptors for pain and temperature are free nerve endings  simple nerve cells beneath skin’s surface  skin receptors send input to somatosensory cortex in brain  phantom limb  amputees experience vivid sensations coming from missing limbs o irritation of nerves that used to originate in limb fools brain into interpreting resulting nerve impulses as real sensations Pain  pain receptors in all body tissues except brain, bones, hair, nails and nonliving parts of teeth  cerebral processing of pain occurs faster than other kinds of tactile stimuli  some tracts in thalamus direct nerve impulses to limbic system, which is involved in motivation and emotion o control emotional component of pain  suffering  both painful sensations and negative emotional response  Gate Control Theory: experience of pain results from opening and closing of gating mechanisms in nervous system o Helps explain why pain is psychological and physical  Endorphins stop pain by inhibiting release of neurotransmitters involved in synaptic transmission of pain impulses Body Senses  Kinesthesis: provides us with feedback about muscles and joints’ positions and movements  Vestibular sense: sense of body orientation or equilibrium o Receptors located in vestibular apparatus of inner ear  canals filled with fluid with hairlike structures as receptors Perception: Creation of Experience  Bottom-up processing: system takes in individual elements of experience and combines them into unified perception o Ex: visual system as you read  Top-down processing: sensory information interpreted in light of existing knowledge, concepts, ideas, and expectations  Attention involves 2 processes of selection o 1. Focusing on certain stimuli o 2. Filtering out other incoming information  inattentional blindness: refers to failure of unattended stimuli to register in consciousness Gestalt Principles of Perpetual Organization  the wholes we perceive are more (and often different from) the sum of their parts  figure-ground relations o we tend to organize stimuli into central/foreground figure and a background  people group and interpret stimuli according to 4 Gestalt laws of perceptual organization  similarity, proximity, closure and continuity o law of similarity: when parts of a configuration are perceived as similar, they will be perceived as belonging together o law of proximity: elements that are near one another are likely to be perceived as part of the same configuration o law of closure: tend to close open edges of a figure or fill in gaps in incomplete figure so identification of form is more compete than what’s actually there) o law of continuity: people link individual elements together so that they form continuous line/pattern that makes sense  Perceptual schema: mental representation or image to compare a stimulus with (to ‘recognize it’)  Perceptual constancies: allow us to recognize familiar stimuli under varying conditions o Shape constancy: allows us to recognize people ad other objects from different angles o Brightness constancy: relative brightness of objects remains same under different conditions of illumination (ex: full sunlight or shade) o Size constancy: perception that size of objects remains relatively constant even though images on our retina change in size with distance Monocular Depth Cues  Light and shadow  Linear perspective: parallel lines converge (angle towards each other) as they recede into distance  Interposition: objects closer to us may cut off part of our view of more distant objects  Height in the horizontal plane  Texture  Clarity  Relative size  Motion parallax: if we are moving, objects nearby appear to move faster in opposite direction Binocular Disparity: each eye sees a slightly different image Convergence: produced by feedback form muscles that turn your eyes inward to view a near object Chapter 6 Reading Notes 10/26/2011 6:36:00 AM  Consciousness: moment-to-moment awareness of ourselves and our environment o Subjective and private  other people don’t know your reality o Dynamic (ever-changing) o Self-reflective and central to our sense of self o Intimately connected with process of selective attention  Freud said mind consists of three levels of awareness o Conscious mind: contains thoughts, perceptions and other mental events of which are currently aware of o Preconscious: outside current awareness, but can be easily recalled o unconscious: can’t be brought into conscious awareness under ordinary circumstances  controlled (effortful) processing: voluntary use of attention and conscious effort  automatic processing: can be performed with little or no conscious effort o happens with routine actions and well-learned tasks  divided attention: ability ot perform more than one activity at the same time  circadian rhythms: biological cycles within the body that occur on an approximately 24-hour cycle o regulated by suprachiasmatic nuclei (SCN)  located in thalamus o SCN reduces melatonin secretions during day and increases it during night  melatonin: hormone that has relaxing effect on body  seasonal affective disorder (SAD): cyclical tendency to become psychologically depressed during certain months of year  rotating shiftwork: forward rotating clock schedule that changes work shifts by extending a worker’s ‘waking day’ rather than compressing it Stages of Sleep  beta waves: a brain wave pattern of 15-30 cycles per second that is characteristic of humans who are in an alert waking stage  alpha waves: brain wave patters of 8-12 cycles per second that is characteristic of humans in a relaxed waking state  stage 1 o brain wave patterns become more irregular, theta waves at 3.5-7.5 cycles per second begin o can be easily awakened  stage 2 o sleep spindles (periodic one-to-two second burst of rapid brain activity) begin o muscles more relaxed, breathing and heart rate are slower o harder to wake up  stage 3 o delta waves: 0.5-2 cycles per second o keep occurring more often  stage 4 o body relaxed, activity in various brain parts has decreased  slow-wave sleep: stages 3 and 4  REM sleep Why do We Sleep?  Restoration model: sleep recharges our rundown bodies and allows us to recover from physical and mental fatigue  what gets restored in our bodies  adenosine o adenosine produced as cells consume fuel, more adenosine signals body to slow down and promotes sleep  evolutionary/circadian sleep models: sleep’s main purpose is to increase a species’ chances of survival in relation to its environmental demands  REM-rebound effect: tendency to increase amount of REM sleep after being deprived of it Sleep Disorders  Insomnia: chronic difficulty in falling asleep, staying asleep, or experiencing restful sleep o Most common sleep disorder; 10-40% of population o Pseudoinsomniacs: complain of insomnia but sleep normally when examined in lab  Narcolepsy: extreme daytime sleepiness, and sudden uncontrollable sleep attack lasting from 1 minute - 1 hour
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