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Ch5__

12 Pages
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Department
Psychology
Course Code
PSY100H1
Professor
Michael Inzlicht

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Chapter 5 Sensation, perception, and attention
Perception is our bridge with the world
In order to perceive, we rely on our sense organs-eyes, ear, skin, nose, tongue
We are only sensitive to limited stimuli
Ways we experience the world into 2 phases: sensation and perception
Sensation: how our sense organs respond to and detect external stimulus energy, and how
those responses are transmitted to the brain
detection
Perception: brains further processing of these signals that ultimately results in an internal
representation of stimuli and conscious experience of the world
Construction of useful and meaningful info about the environment
Eg. Green light emits photo sensed by eye and transmit signal to brain sensation
Brain processes neural signals and observer experiences a green light (perception)
Study of bodily systems that convert stimulus energy into useful info
How do we sense our worlds?
Evolved through time
Stimuli must be coded to be understood by the brain
Sensory coding
Different physical environment coded by diff patterns of neural impulses
Receptors are specialized neurons in the sense organ that pass impulses to connecting neurons
when they receive phy or chemical stimulation- TRANSDUCTION
Transmit info to brain in form of neural impulse
Sensory info must go through thalamus then send info to cortex interpreted as sight, smell,
sound, touch, taste
Sensory code divided into 2 categories: quantitative and qualitative
Intensity, brightness… determined by firing frequency
Colour, taste
Different receptors types for different stimulus
In most sensory systems, except smell, receptors provide coarse coding, coded by only a
few receptors responding to many stimuli
Psychophysics relates stimulus to response
Psych and physical stimuli
Developed by Gustav Fechner: how much physical energy needed for us to sense
Sensory thresholds:
Absolute threshold: min intensity of stimulation before we can experience a
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sensation
Eg. Faintest sound we can hear
Difference threshold: noticeable difference between two stimuli
Min amount of change required for us to detect a difference
Webers law: the size of a noticeable diff is based on a relative proportion of difference
rather than a fixed amount of difference
Eg. 96/100 and 6/10
Signal detection theory:
Flaw to absolute threshold, forgot to account for human judgment
Detecting stimulus requires making judgment about its presence or absence, based on a
subjective interpretation of ambiguous info
Trials to judge whether stimulus was present or not
Hit (y/y), miss(y/n), false alarm (n/y), correct rejection (n/n)
Response bias refers to participants tendency to report detecting the stimulus on
ambiguous trials
Eg. Doctor may tend to say abnormality because treatment doesnt harm patients
Compare hit vs. false alarm
Sensory Adaptation
Sensitivity to stimuli decreases over time
Tuned to detect changes in environment, less critical to keep responding to unchanging
stimuli
Eg. Construction noise while reading
What are the basic sensory processes?
Taste, smell, touch, hear, vision
In gustation, taste buds are chemical detectors
Taste receptor are taste buds of tongue and mouth
Microvilli at tip of tongue contact with saliva, stimulate signal to brainstem region called
medulla and to thalamus and cortex, produce experience of taste
Taste receptors: sweet, sour, salty, bitter
Diff taste buds are spread uniformly throughout tongue and mouth
Taste relies heavily on sense of smell, texture,
Taste experience occurs in brain
Integration of sensory signals that gives us the experience of taste
Intense taste sensation supertaster-6 times taste buds as normal taster
Theyre picky eaters, because some taste seem overwhelming
More sensation isnt always better
In smell, the nasal cavity gathers particles of odour
Sensing chemical from outside body
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Contact with olfactory epithelium embedded with olfactory receptor
Trigger chemical receptor and nerve impulses convey info to olfactory bulb
Brain center for smell, below frontal lobes
Smell bypass thalamus directly to brain areas
Prefrontal cortex process info about whether a smell is pleasant or aversive
Amygdala process intensity of smell
Thousands of diff receptors in olfactory epithelium, responsive to diff chem. Group
How receptor recognize odour not known: specific smell, or by amt of receptor activated
Animals have stronger olfactory capabilities because we rely on more vision and other senses
Smell evoke moods eg. Mouthwash
Pheromones recognized by specialized receptors in nasal cavity behavioural reaction in
animals, sexual signaling in animals and humans, menstrual cycle synchronization
In touch, sensor in the skin detect pressure, temp and pain
Haptic sense
Tactile stimulation with skin
Haptic receptors are sensory neurons that terminate in the outer layer of skin
Long axons enter cns by spinal or cranial nerves
Receptor at base of hair follicles, capsules in skin
Separate receptor for hot and cold
Why cant tickle yourself: brain areas involved in touch sensation respond less to self
produced tactile stimulation than to external tactile stimulation
Two types of pain
Warning system
Genetic disorder in children insensitive to pain usually die young
Actual experience of pain created by brain
Eg. Amputated limb feel phantom pain in nonexistent limb because of misinterpretation
of neural activity
Damage skin activate haptic receptor
Nerve fibers that convey pain are thinner than others, found in all body tissue that sense pain
Fast and slow fiber
Fast pain receptor activated by strong physical pressure and temp extremes
Slow acting receptor activated by chemical change in tissue when skin is damaged
Fast pain allows recoil, slow pain allows keep away from using affected part
Gate control theory
By Ronald melzack
In order for us to experience pain, pain receptors must be activated and a neural gate in spinal
cord must allow these signals through to the brain
Close gate by stimulating other haptic receptor eg. Scratching itch satisfying
Overwhelms signals from pain receptor and reduce itch
Cognitive state can close gate, distraction
One region of midbrain influences wheter gate is open or shut
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Description
Chapter 5 Sensation perception and attentionPerception is our bridge with the worldIn order to perceive we rely on our sense organseyes ear skin nose tongueWe are only sensitive to limited stimuliWays we experience the world into 2 phases sensation and perceptionSensation how our sense organs respond to and detect external stimulus energy and how those responses are transmitted to the braindetectionPerception brains further processing of these signals that ultimately results in an internal representation of stimuli and conscious experience of the worldConstruction of useful and meaningful info about the environmentEg Green light emits photo sensed by eye and transmit signal to brain sensationBrain processes neural signals and observer experiences a green light perceptionStudy of bodily systems that convert stimulus energy into useful infoHow do we sense our worldsEvolved through timeStimuli must be coded to be understood by the brainSensory codingDifferent physical environment coded by diff patterns of neural impulsesReceptors are specialized neurons in the sense organ that pass impulses to connecting neurons when they receive phy or chemical stimulation TRANSDUCTIONTransmit info to brain in form of neural impulseSensory info must go through thalamus then send info to cortex interpreted as sight smell sound touch tasteSensory code divided into 2 categories quantitative and qualitativeIntensity brightness determined by firing frequencyColour tasteDifferent receptors types for different stimulusIn most sensory systems except smell receptors provide coarse coding coded by only a few receptors responding to many stimuliPsychophysics relates stimulus to responsePsych and physical stimuliDeveloped by Gustav Fechner how much physical energy needed for us to senseSensory thresholdsmin intensity of stimulation before we can experience a Absolute threshold wwwnotesolutioncomsensationEg Faintest sound we can hear noticeable difference between two stimuliDifference thresholdMin amount of change required for us to detect a differenceWebers law the size of a noticeable diff is based on a relative proportion of difference rather than a fixed amount of differenceEg 96100 and 610Signal detection theoryFlaw to absolute threshold forgot to account for human judgmentDetecting stimulus requires making judgment about its presence or absence based on a subjective interpretation of ambiguous infoTrials to judge whether stimulus was present or notHit yy missyn false alarm ny correct rejection nnResponse bias refers to participants tendency to report detecting the stimulus on ambiguous trialsEg Doctor may tend to say abnormality because treatment doesnt harm patientsCompare hit vs false alarmSensory AdaptationSensitivity to stimuli decreases over timeTuned to detect changes in environment less critical to keep responding to unchanging stimuliEg Construction noise while readingWhat are the basic sensory processesTaste smell touch hear visionIn gustation taste buds are chemical detectorsTaste receptor are taste buds of tongue and mouthMicrovilli at tip of tongue contact with saliva stimulate signal to brainstem region called medulla and to thalamus and cortex produce experience of tasteTaste receptors sweet sour salty bitterDiff taste buds are spread uniformly throughout tongue and mouthTaste relies heavily on sense of smell textureTaste experience occurs in brainIntegration of sensory signals that gives us the experience of tasteIntense taste sensationsupertaster6 times taste buds as normal taster Theyre picky eaters because some taste seem overwhelmingMore sensation isnt always betterIn smell the nasal cavity gathers particles of odourSensing chemical from outside bodywwwnotesolutioncom
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