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Chapter 5

PSY100 Chapter 5

7 Pages
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Department
Psychology
Course Code
PSY100H1
Professor
Dan Dolderman

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Chapter 5- Sensation and Perception
Sensation: the sense organs’ responses to external stimuli and the transmission of these
responses to the brain
Perception: the processing and interpretation of sensory signals, it results in an internal
representation of that stimulus
Sensory coding: sensory organs’ translations of stimuli’s physical properties into neural
impulses
1. Transduction: sensory receptors pass impulses to connecting neurons when they
receive physical/chemical stimulation
2. Connecting neurons transmit info to brain in the form of neural impulse pass by
thalamus cerebral cortex- incoming neural impulses interpret it as sight, smell, sound,
touch or taste (Perception)
Qualitative info: light change from green red, different receptors respond to
different stimuli
Quantitative info: light goes brighter same receptors fire more rapidly
* Coarse coding: sensory qualities coded by few receptors that respond to broad range of
stimuli
Psychophysics: Ernst Weber and Gustav Fechner- examines our psychological
experiences of physical stimuli
Examines how much physical energy is require for our organs to detect stimulus, how
much change is required before we notice change
Sensory thresholds
Absolute threshold: minimum intensity of stimulation that must occur before you
experience a sensation
Difference threshold: minimum amount of change required for a person to detect a
difference between 2 stimuli
Difference threshold ↑’s as stimulus becomes more intense= Weber’s law
(difference is based on proportion of original stimulus vs. actual difference)
Ex: picking up pen stapler vs. textbook and slightly heavier textbook
Signal Detection Theory
States that detecting a faint stimulus requires a subjective judgement- not just all-or-
none response
Ex: radiologist- detecting tumour- knowledge of patient’s history, age, consequence
of his prognosis, all affect his judgement
Any trial in which participants judge whether an event occurs has 1 of 4 outcomes:
1. Hit: signal present and observer detects it
2. Miss: signal present, observer misses it
3. False alarm: observer detects signal, no signal
4. Correct rejection: no signal, no detection
* compare hit rate with false alarm rate participant’s sensitivity to signal (validity)
Response bias: Amount of evidence needed for observer to say signal is present
Ex: radiologist needs a lot of evidence to make sure tumour is there vs. doctor looking
at broken bone (having a cast on not as big of a deal if mistake vs. cancer treatment)
Sensory adaptation
Decrease in sensitivity to a constant level of stimulation or noticing stimulus is gone
after constant presence
Ex: working in library construction outside, stop noticing it after awhile
Basic Sensory Processes
1. Gustation: sense of taste
Taste buds cranial nerve
Supertasters: people who experience intense taste sensations (genetics)
Cultural factors influence taste as well- mothers pass down eating preferences on to
offspring in womb
2. Olfaction: sense of smell
Most direct route to brain (NO RELAY IN THAMALUS)
Odorants pass into nasal cavity olfactory receptors in olfactory epithelium
transmit signal to olfactory bulb (brain centre for smell) olfactory nerve
Prefrontal cortex- process whether smell is good or bad
Amygdala- processes intensity of smell
3. Hepatic sense- touch
Conveys sensations of temperature, pressure, pain and sense of where limbs are in
space
Hepatic receptors- sensory neurons on skin’s outer layer transmit signal to
trigeminal nerve (above neck) or spinal nerve (below neck
2 types of nerve fibres associated with pain, depending on amount of myelination
1. fast fibres: fast, sharp pain (protective)
2. slow fibres: chronic, dull, steady pain (recuperation)
Gate control theory of pain
pain is perceptual experience rather than simply response to nerve stimulation
states that for us to experience pain, pain receptors must be activated and a neural
“gate” in the spinal cord must allow to signals through to the brain
pain can be blocked at spinal cord level before gets to brain by larger sensory
nerve fibres ex: distraction, numbing cream at dentist closes gate vs. worrying
focusing on painful stimulus opens gate

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Description
Chapter 5- Sensation and Perception Sensation: the sense organs’ responses to external stimuli and the transmission of these responses to the brain Perception: the processing and interpretation of sensory signals, it results in an internal representation of that stimulus Sensory coding: sensory organs’ translations of stimuli’s physical properties into neural impulses 1. Transduction: sensory receptors pass impulses to connecting neurons when they receive physical/chemical stimulation 2. Connecting neurons transmit info to brain in the form of neural impulse pass by thalamus cerebral cortex- incoming neural impulses interpret it as sight, smell, sound, touch or taste (Perception) • Qualitative info: light change from green red, different receptors respond to different stimuli • Quantitative info: light goes brighter same receptors fire more rapidly * Coarse coding: sensory qualities coded by few receptors that respond to broad range of stimuli Psychophysics: Ernst Weber and Gustav Fechner- examines our psychological experiences of physical stimuli • Examines how much physical energy is require for our organs to detect stimulus, how much change is required before we notice change Sensory thresholds • Absolute threshold: minimum intensity of stimulation that must occur before you experience a sensation • Difference threshold: minimum amount of change required for a person to detect a difference between 2 stimuli • Difference threshold ↑’s as stimulus becomes more intense= Weber’s law (difference is based on proportion of original stimulus vs. actual difference) Ex: picking up pen stapler vs. textbook and slightly heavier textbook Signal Detection Theory • States that detecting a faint stimulus requires a subjective judgement- not just all-or- none response • Ex: radiologist- detecting tumour- knowledge of patient’s history, age, consequence of his prognosis, all affect his judgement • Any trial in which participants judge whether an event occurs has 1 of 4 outcomes: 1. Hit: signal present and observer detects it 2. Miss: signal present, observer misses it 3. False alarm: observer detects signal, no signal 4. Correct rejection: no signal, no detection * compare hit rate with false alarm rate participant’s sensitivity to signal (validity) Response bias: Amount of evidence needed for observer to say signal is present Ex: radiologist needs a lot of evidence to make sure tumour is there vs. doctor looking at broken bone (having a cast on not as big of a deal if mistake vs. cancer treatment) Sensory adaptation • Decrease in sensitivity to a constant level of stimulation or noticing stimulus is gone after constant presence • Ex: working in library construction outside, stop noticing it after awhile Basic Sensory Processes 1. Gustation: sense of taste • Taste buds cranial nerve • Supertasters: people who experience intense taste sensations (genetics) • Cultural factors influence taste as well- mothers pass down eating preferences on to offspring in womb 2. Olfaction: sense of smell • Most direct route to brain (NO RELAY IN THAMALUS) • Odorants pass into nasal cavity olfactory receptors in olfactory epithelium transmit signal to olfactory bulb (brain centre for smell) olfactory nerve • Prefrontal cortex- process whether smell is good or bad • Amygdala- processes intensity of smell 3. Hepatic sense- touch • Conveys sensations of temperature, pressure, pain and sense of where limbs are in space • Hepatic receptors- sensory neurons on skin’s outer layer  transmit signal to trigeminal nerve (above neck) or spinal nerve (below neck 2 types of nerve fibres associated with pain, depending on amount of myelination 1. fast fibres: fast, sharp pain (protective) 2. slow fibres: chronic, dull, steady pain (recuperation) Gate control theory of pain • pain is perceptual experience rather than simply response to nerve stimulation • states that for us to experience pain, pain receptors must be activated and a neural “gate” in the spinal cord must allow to signals through to the brain • pain can be blocked at spinal cord level before gets to brain by larger sensory nerve fibres ex: distraction, numbing cream at dentist closes gate vs. worrying focusing on painful stimulus opens gate • pain is both a sensory experience and an emotional response (processed by 2 different regions in brain) nd 3. audition- sense of sound perception (2 to vision) • change in vibrations in air pressure produce sound waves • amplitude- determines its loudness • frequency-determines its pitch • sound waves outer ear- make eardrum vibrate middle ear- cause ossicles and oval window to vibrate creates pressure waves in inner’s ear’s fluid, bends hair cells cause neurons to fire auditory nerve • auditory localization: we use both intensity and timing of sounds to locate where they are coming from (if sound reaches right ear first, know it’s coming from right) 4. Vision Cornea: first structure light interacts with, where most refraction occurs (change in direction of light) Pupil: dark circle in back of eye Iris: coloured muscle, contract/relax control amount of light lets in Retina: where all photoreceptive cells are, coverts light into AP’s “projection screen” • Cones: colour vision • Rods: sensitive to hard dark/bright area is Fovea: within retina, where most colour-sensitive photoreceptive cells are Optic nerve: where all cell axons leave the eye • Blind spot: no photoreceptive cells Optic chiasm: ½ info crosses over to other side of brain o Optic nerve optic chiasm thalamus 1 visual cortex Cornea flips world • R side of visual world projects onto L side of eye/retina • L side of L eye stays on same side • L side of R eye crosses over • R side of world left cerebral hemisphere • receptive field: region of visual space to which neurons in the primary visual cortex and sensitive • consists of centre and a surrounding region- light is shined at centre, neural firing increases, when light is directed to surrounding region, neural firing decreases, no light cells fire at baseline rate • lateral inhibition: visual process in which adjacent photoreceptors tend to inhibit one another (emphasizes changes in visual stimuli- sensitive to edges, where objects end) • Hermann grid • Colour of light is determined by its wavelength
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