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Chapter 5

ch. 5 textbook notes - only important things you should know for test


Department
Psychology
Course Code
PSY100H1
Professor
Michael Inzlicht
Chapter
5

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Psych Notes: Chapter 5
Sensation, Perception and Attention
- The way we experience our world is often divided into two parts: Perception, Sensation
o Sensation: how our sense organs respond to and detect external stimulus energy and
how those responses get transmitted to brain
o W]}vW]v[(µZ}]vP}(Z]PvoZµo]uoÇµo]v
an internal rep of stimuli and a conscious experience of a world
- How do we sense our worlds?
o Sensory organs convert forms of physical energy into signals brain understands
o Stimuli must be coded to be understood by the brain
^v}Ç}]vPWZÁÇ}µv}Ç}Pvvo]uµ[ZÇ]o
prop. Into neural impulses
Transduction: the process where receptors are specialized neurons in the sense
organs that pass impulses to connecting neurons when they receive some sort
of physical or chemical stimulation
x Most sensory info passes to thalamus Æ sends info to cortex, where
incoming neural impulses are interpreted as sight, smell, sound, touch,
or taste
Sensory coding can be divided into 2 categories:
x Quantitative t intensity, brightness, loudness, Æ }]vP[µµooÇ
indexed by neural firing frequency (sensation)
x Qualitative t (color or taste) diff sensory receptors respond to diff
qualities of a stimulus // a dedicated receptor type for every possible
stimulus (maybe), or most cases receptors provide coarse coding:
sensory qualities are coded by only a few receptors, each of which
respond to a broad range of stimuli
x SEE TABLE 5.1 PG 163
Psychophysics Relates Stimulus to Response
x Psychophysics: examines our psychological experiences of physical
stimuli
x Sensory Thresholds
o Absolute threshold: minimum intensity of stimulation that must
occur before we can experience a sensation
o Difference Threshold: the just noticeable diff between two
stimuli (min. amt of change required for us to detect a diff)
t[>ÁWZ}(iµv}]o]((]
on a relative proportion of difference rather than a
fixed amt of diff (i.e., 6/10 vs 96/100)
x Signal Detection Theory
o Concept of absolute threshold was flawed
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Signal detection theory: ppl believed they saw a weak
stimulus when there was none and sometimes failed to
detect stimulus presented Æ detecting stiumulus
requires making judgment about its presence or
absence based on subjective interpretation of
ambiguous info
Z}v]W]]v[s tendency to report
detecting the stimulus on ambiguous trials
x Expectations influence extent of bias
x ^v}Ç]}vWÁZv}À[nsitivity to stimuli decreases
over time Æ cuz sensory is tuned to detect changes in environment
- What are the Basic Sensory Processes?
o In Gustation, Taste Buds are Chemical Detectors
Chemical substances from food that dissolve in saliva Æ microvilli from each
taste bud sends electrical signals to medulla in the brainstem region when
stimulated and from there to the thalamus and cortex Æ produce taste
Diff taste buds are spread relatively uniformly thruout tongue & mouth
Entire taste experience occurs in your brain
o In Smell, the nasal cavity gathers particles of odour
Olfaction: most direct route to the brain of all senses
Odours come in contact with olfactory epithelium (a thin layer of tissue
embedded w olfactory receptors)
x Particles dissolve in the solution around the epithelium and causes
reaction that triggers chemical receptorsÆ convey info to olfactory
bulb (brain center for smell just below frontal lobes)
x Bypasses thalamus. Prefrontal cortex = pleasant or not// Amygdala =
intensity of smell // These regions are also involved in xperience of
emotion and memory formation so SMELL can evoke powerful memory
and feelings
How they encode diff smells?? Possibility 1: every smell has a
receptor//possibility 2: pattern of activation determine percept of smell
Pheromones: chemicals released by animals that trigger physiological or
behavioral reactions in other animals
o In Touch, sensors in skin detect pressure, temperature, and Pain
Haptic sense: touch.
Tactile stimulation: anything that makes contact w our skin
x Capsules in skin, nerve fibres at bases of hair follicles,
Separate receptors for hot and cold
Two types of pain
x Damages to skin Æ haptic receptors
x 2 kinds of nerve fibers
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o Fast fibres: sharp, immediate pain, (myelinated)
o Slow fibres: chronic, dull, steady pain (not myelinated)
Gate-Control Theory: in order for us to experience pain, pain receptors must be
]Àvvµo^P_]vZ]vo}uµoo}ÁZ]PvoZ}µPZ
to the brain
x One way to close the gate is to stimulate other haptic receptors, which
overwhelms the signals from pain receptors
x One region of midbrain influences whether gate is open or shut
o Block pain signals from reaching cortex (ex. Endorphins)
o In hearing the ear is a sound wave detector
Sound wave: the pattern of changes in air pressure through time
x Amplitude: loudness // frequency: pitch
x Sound waves Æ outer ear Æ auditory canal Æ eardrum [beginning of
the middle ear] Æ vibration transferred to ossicles (3 tiny bones) Æ
oval window (membrane of the cochlea) (read pg.170)
Time and place coding for pitch
x Temporal coding: used for relatively low frequencies (ex. Sound of tuba)
Æ firing rate of hair cells match frequency of auditory stimulation (can
only occur for relatively low Hz [up to 4000], at higher Hz, they fire in
volleys
x Place coding: mechanism for encoding high-frequency auditory stiumuli
in which frequency of the sound wave is encoded by location of the hair
cells along the basilar membrane
Concurrent processing to locate sounds
x Timing cue and intensity cue tell about location
x Kind of unknown for humans
o In Vision, the Eye Detects Light Waves
Seeing: intelligent process that occurs in brain to produce useful info about
environment
Retina, pupil, iris, cornea, lens, accommodation
Rods and Cones: 2 types of receptor cells in retina
x Rods :respond at extremely low levels of illumination/primarily
}v]o(}v]PZÀ]]}vl}v[µ}}o}À]]}vl}}}oÀ]vP
fine detail // all located at edge of retina [none in fovea]
o Look at dimly lit star (appears to disappear)
x Cones: less sensitive to low levels of light Æ primarily responsible for
vision under high illumination and for color and detail // densely packed
in center of retina (called fovea) & [spread thru-out retina]
x Photopigments: w/in rods and cones// light sensitive chemicals initiate
the transduction of light waves into electrical neural impulses
Transmission from Eye to Brain
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