Transcript Module 5 - Doral Academy High School

Sensation and Perception
THREE DEFINITONS
• Adaptation:
– the decreasing response of the sense organs, the
more they are exposed to a continuous level of
stimulation
• Sensation versus perception:
– relatively meaningless bits of information that result
when the brain processes electrical signals that come
from the sense organs
– perceptions:
– meaningful sensory experiences that result after the
brain combines hundreds of sensations
THREE DEFINITONS (CONT.)
• eyes, ears, nose, skin, and tongue are complex,
miniaturized, living sense organs that automatically
gather information about your environment
• Transduction:
– process in which a sense organ changes, or
transforms, physical energy into electrical signals that
become neural impulses, which may be sent to the
brain for processing
PERCEPTUAL THRESHOLDS
• Threshold
– a point above which a stimulus is perceived and
below which it is not perceived
– threshold determines when we first become aware of
a stimulus
PERCEPTUAL THRESHOLDS (CONT.)
• Becoming aware of a stimulus
– Gustav Fechner
• defined the absolute threshold as the smallest
amount of stimulus energy (such as sound or light)
that can be observed or experienced
– Absolute threshold
• the intensity level of a stimulus such that a person
will have a 50% chance of detecting it
SUBLIMINAL PERCEPTION
• Subliminal Message
– brief auditory or visual message that is presented
below the absolute threshold
– means that there is less than a 50% chance that the
message will be perceived
• Self-fulfilling prophecies
– involve having strong beliefs about changing some
behavior and then acting, unknowingly, to change that
behavior
PERCEPTUAL THRESHOLDS (CONT.)
• Subliminal stimulus
– has an intensity that gives a person less than a 50%
chance of detecting the stimulus
– breast cancer
• accuracy problems
– looking for ways to lower the threshold for
detecting cancerous tumors and thus save
patients
– recently, use of digital mammograms (allows
for images to be enhanced or magnified) is
better in detecting cancerous tumors in women
PERCEPTUAL THRESHOLDS (CONT.)
• E. H. Weber
– worked on the problem of how we judge whether a
stimulus, such as loud music, has increased or
decreased in intensity
– concept of just noticeable difference (JND)
– refers to the smallest increase or decrease in the
intensity of a stimulus that a person is able to detect
• Weber’s law
– The increase in intensity of a stimulus needed to
produce a just noticeable difference grows in
proportion to the intensity of the initial stimulus.
SENSATION VERSUS PERCEPTION
• Basic Differences
– Sensations
• our first awareness of some outside stimulus
• outside stimulus activates sensory receptors,
which in turn produce electrical signals that are
transformed by the brain into meaningless bits of
information
– Perceptions
• the experience we have after our brain assembles
and combines thousands of individual sensations
into a meaningful pattern or image
SENSATION VERSUS PERCEPTION (CONT.)
• Changing sensation into perception
– Stimulus
• change of energy in the environment, such as light
waves, sound waves, mechanical pressure, or
chemicals
– Transduction
• change physical energy into electrical signals
• electrical signals are changed into impulses that
travel into the brain
– Brain
• impulses from senses first go to different primary
areas of the brain
SENSATION VERSUS PERCEPTION (CONT.)
• Changing sensation into perception
– brain: association areas
– sensation impulses are sent to the appropriate
association area in the brain
• Personalized perceptions
– each of us has a unique set of personal experiences,
emotions, and memories that are automatically added
to our perceptions by other areas of the brain
EYE: VISION
• Structure and function
– eyes perform two separate processes
– first: gather and focus light into precise area in the
back of eye
– second: area absorbs and transforms light waves into
electrical impulses
– process called transduction
EYE: VISION (CONT.)
• Stimulus: Light Waves
– Invisible—too short
• wave lengths too short
• gamma rays, x-rays, ultraviolet rays
– Visible—just right
• Visible spectrum
• Particular segment of electromagnetic energy that
we can see because these waves are the right
length to stimulate receptors in the eye
– Invisible—too long
• wave lengths longer
• Radar, FM, TV, shortwave, AM
EYE: VISION (CONT.)
EYE: VISION (CONT.)
• Structure and function
– Vision: 7 steps
• Image reversed
• Light waves
• Cornea
• Pupil
• Iris
• Lens
• Retina
EYE: VISION (CONT.)
• Structure and function
– Image reversed
• In the back of the eye, objects appear upside
down.
• somehow the brain turns the objects right side up
– Light waves
• light waves are changed from broad beams to
narrow, focused ones
EYE: VISION (CONT.)
• Structure and function
– Cornea
• rounded, transparent covering over the front of
your eye
– Pupil
• round opening at the front of the eye that allows
light waves to pass into the eye’s interior
EYE: VISION (CONT.)
• Structure and function
– Iris
• circular muscle that surrounds the pupil and
controls the amount of light entering the eye
– Lens
• transparent, oval structure whose curved surface
bends and focuses light waves into an even
narrower beam
EYE: VISION (CONT.)
• Structure and function
– Retina
• located at the very back of the eyeball, is a thin film
that contains cells that are extremely sensitive to
light
• light sensitive cells, called photoreceptors, begin
the process of transduction by absorbing light
waves
EYE: VISION (CONT.)
EYE: VISION (CONT.)
• Retina:
– three layers of cells
• back layer contains two kinds of photoreceptors
that begin the process of transduction
• change light waves into electrical signals
• rod located primarily in the periphery
• cone located primarily in the center of the retina
called the fovea
EYE: VISION (CONT.)
• rods:
– photoreceptor that contain a single chemical, called
rhodopsin
– activated by small amounts of light
– very light sensitive
– allow us to see in dim light
– see only black, white and shades of gray
EYE: VISION (CONT.)
• cones:
– photoreceptors that contain three chemicals called
opsins
– activated in bright light
– allow us to see color
– cones are wired individually to neighboring cells
– allows us to see fine detail
EYE: VISION (CONT.)
EYE: VISION (CONT.)
• Visual pathways: Eye to brain
– Optic nerve
– Primary visual cortex
– Visual association areas
EYE: VISION (CONT.)
EYE: VISION (CONT.)
• Visual pathways: eye to brain
– Optic nerve
• nerve impulses flow through the optic nerve as it
exits from the back of the eye
• the exit point is the “blind spot”
• the optic nerves partially cross and pass through
the thalamus
• the thalamus relays impulses to the back of the
occipital lobe in the right and left hemisphere
EYE: VISION (CONT.)
• Visual pathways: eye to brain
– Primary visual cortex
• the back of the occipital lobes is where primary
visual cortex transforms nerve impulses into simple
visual sensations
– Visual association areas
• the primary visual cortex sends simple visual
sensations to neighboring association areas
EYE: VISION (CONT.)
• Color Vision
– Trichromatic theory
• three different kinds of cones in the retina
• each cone contains one of the three different lightsensitive chemicals, called opsins
• each of the three opsins is most responsive to
wavelengths that correspond to each of the three
primary colors
• blue, green, red
• all colors can be mixed from these primary colors
EYE: VISION (CONT.)
• Opponent-Process Theory
– Afterimage
• visual sensation that continues after the original
stimulus is removed
• ganglion cells in retina and cells in thalamus
respond to two pairs of colors—red-green and
blue-yellow
• when excited, respond to one color of the pair
• when inhibited, respond to complementary pair
EYE: VISION (CONT.)
• Color Blindness
– inability to distinguished two or more shades in the
color spectrum
– Monochromatic:
• total color blindness
• black and white
• result of only rods and one kind of functioning cone
– Dichromatic:
• trouble distinguishing red from green
• two kinds of cones
• inherited genetic defect
• mostly in males
• See mostly shades of green
RULES OF ORGANIZATION
• Structuralist versus Gestalt psychologists
– Structuralists
• believed that you add together hundreds of basic
elements to form complex perceptions
– Gestaltists
• believe our brains follow a set of rules that specify
how individual elements are to be organized into a
meaningful pattern, or perception
RULES OF ORGANIZATION (CONT.)
• Organizational rules
– rules of organization: identified by Gestalt
psychologists
• specify how our brains combine and organize
individual pieces or elements into a meaningful
perception
– Figure-ground
• states: in organizing stimuli, we tend to
automatically distinguish between a figure and a
ground
– Similarity
• states: in organizing stimuli, we group together
elements that appear similar
RULES OF ORGANIZATION (CONT.)
– Closure
• states: in organizing stimuli, we tend to fill in any
missing parts of a figure and see the figure as
complete
– Proximity
• states: in organizing stimuli, we group together
objects that are physically close to one another
– Simplicity
• states: stimuli are organized in the simplest way
possible
– Continuity
• states: in organizing stimuli, we tend to favor the
smooth or continuous paths when interpreting a
series of points or lines
PERCEPTUAL CONSTANCY
• Size, shape, brightness & color constancy
– Size constancy
• refers to our tendency to perceive objects as
remaining the same size even when their images
on the retina are continually growing or shrinking
– Shape constancy
• refers to our tendency to perceive an object as
retaining its same shape even though when we
view it from different angles, its shape is
continually changing its image on the retina
PERCEPTUAL CONSTANCY (CONT.)
• Size, shape, brightness & color constancy
– Brightness constancy
• refers to the tendency to perceive brightness as
remaining the same in changing illumination
– Color constancy
• refers to the tendency to perceive colors as
remaining stable despite differences in lighting
DEPTH PERCEPTION
• Binocular (two eyes) depth cues
– Depth perception
• refers to the ability of your eye and brain to add a
third dimension, depth, to all visual perceptions,
even though images projected on the retina are in
only two dimensions, height, and width
– Binocular depth cues
• depends on the movement of both eyes
– Convergence
• refers to a binocular cue for depth perception
based on signals sent from muscles that turn the
eyes
DEPTH PERCEPTION (CONT.)
• Retinal disparity
– refers to a binocular depth cue that depends on the
distance between the eyes
DEPTH PERCEPTION (CONT.)
DEPTH PERCEPTION (CONT.)
• Monocular depth cues
– produced by signals from a single eye
– Linear perspective
• monocular depth cue that results as parallel lines
come together, converge, in the distance
– Relative size
• monocular depth cue that results when we expect
two objects to be the same size and they are not
– Interposition
• monocular depth cue that comes into play when
objects overlap
DEPTH PERCEPTION (CONT.)
• Monocular depth cues
– Light and shadow
• monocular depth cues where brightly lit objects
appear closer, while objects in shadows appear
farther away
– Texture gradient
• monocular depth cue in which areas with sharp,
detailed texture are interpreted as being closer and
those with less sharpness and poorer detail are
perceived as more distant
DEPTH PERCEPTION (CONT.)
• Monocular depth cues
– Atmospheric perspective
• monocular depth cue that is created by the
presence of dust, smog, clouds, or water vapor
– Motion parallax
• monocular depth cue based on the speed of
moving objects
ILLUSIONS
• Strange perceptions
– Illusion
• a perceptual experience in which you perceive an
image as being so strangely distorted that, in
reality, it cannot and does not exist
– Impossible figure
• perceptual experience in which a drawing seems
to defy basic geometric laws
ILLUSIONS (CONT.)
EAR: AUDITION
• Stimulus:
– Sound waves
• stimuli for hearing (audition)
• ripples of different sizes
• sound waves travel through space with varying
heights and frequency
– Height
• distance from the bottom to the top of a sound
wave
• called amplitude
– Frequency
• number of sound waves occurring within one
second
EAR: AUDITION (CONT.)
• Loudness
– subjective experience of a sound’s intensity
– brain calculates loudness from specific physical
energy (amplitude of sound waves)
• Pitch
– subjective experience of a sound being high or low
– brain calculates from specific physical stimuli
– speed or frequency of sound waves
– measured in cycles (how many sound waves in one
second)
EAR: AUDITION (CONT.)
• Measuring sound waves
– decibel: unit to measure loudness
– threshold for hearing:
• 0 decibels (no sound)
• 140 decibels (pain and permanent hearing loss)
EAR: AUDITION (CONT.)
EAR: AUDITION (CONT.)
• Outer, middle, and inner ear
– Outer ear
• consists of three structures
• external ear
• auditory canal
• tympanic membrane
EAR: AUDITION (CONT.)
• Outer, middle, and inner ear
– Outer ear
• external ear
– oval shaped structure that protrudes from the
side of the head
• function
– pick up sound waves and then send them down
the auditory canal
EAR: AUDITION (CONT.)
• Outer, middle, and inner ear
– Outer ear
• auditory canal
– long tube that funnels sound waves down its
length so that the waves strike the tympanic
membrane (ear drum)
EAR: AUDITION (CONT.)
• Outer, middle, and inner ear
– Outer ear
• tympanic membrane
– taut, thin structure commonly called the
eardrum
– Sound waves strike the tympanic membrane
and cause it to vibrate
EAR: AUDITION (CONT.)
EAR: AUDITION (CONT.)
• Outer, middle, and inner ear
– Middle ear
• bony cavity sealed at each end by membranes.
• the membranes are connected by three tiny bones
called ossicles
• hammer, anvil and stirrup
– hammer is attached to the back of the tympanic
membrane
– anvil receives vibrations from the hammer
– stirrup makes the connection to the oval
window (end membrane)
EAR: AUDITION (CONT.)
• Outer, middle, and inner ear
– Inner ear
• contains two structures sealed by bone
– cochlea: involved in hearing
– vestibular system: involved in balance
EAR: AUDITION (CONT.)
• Cochlea
– bony coiled exterior that resembles a snail’s shell
– contains receptors for hearing
– function is transduction
– transforms vibrations into nerve impulses that are
sent to the brain for processing into auditory
information
EAR: AUDITION (CONT.)
EAR: AUDITION (CONT.)
• Auditory brain areas
– sensations and perceptions
– two step process occurs after the nerve impulses
reach the brain
– primary auditory cortex
– top edge of temporal lobe
– transforms nerve impulses into basic auditory
sensations
– auditory association area
– combines meaningless auditory sensations into
perceptions, which are meaningful melodies, songs,
words, or sentences
VESTIBULAR SYSTEM: BALANCE
• Position and balance
– vestibular system is located above the cochlea in the
inner ear
– includes semicircular canals
– bony arches set at different angles
– each semicircular canal is filled with fluid that moves
in response to movements of your head
– canals have hair cells that respond to the fluid
movement
– function of vestibular system
– include sensing the position of the head, keeping the
head upright, and maintaining balance
CHEMICAL SENSES
• Taste
– chemical sense because the stimuli are various
chemicals
– tongue
– surface of the tongue
– taste buds
CHEMICAL SENSES (CONT.)
• Tongue
– Five basic tastes
• sweet
• salty
• sour
• bitter
• umami: meaty-cheesy taste
CHEMICAL SENSES (CONT.)
• Surface of the tongue
– chemicals, which are the stimuli for taste, break down
into molecules
– molecules mix with saliva and run into narrow
trenches on the surface of the tongue
– molecules then stimulate the taste buds
CHEMICAL SENSES (CONT.)
• Taste buds
– shaped like miniature onions
– receptors for taste
– chemicals dissolved in saliva activate taste buds
– produce nerve impulses that reach areas of the
brain’s parietal lobe
– brain transforms impulses into sensations of taste
• Flavor
– combination of taste and smell
CHEMICAL SENSES (CONT.)
CHEMICAL SENSES (CONT.)
• Smell, or olfaction
– Steps for olfaction
• Stimulus
• Olfactory cells
• Sensation and memories
• Functions of olfaction
CHEMICAL SENSES (CONT.)
CHEMICAL SENSES (CONT.)
• Smell, or olfaction
– Stimulus
• we smell volatile substances
• volatile substances are released molecules in the
air at room temperature
• example:
– skunk spray, perfumes, warm brownies; not
glass or steel
CHEMICAL SENSES (CONT.)
• Smell, or olfaction
– Olfactory cells
• receptors for smell are located in a I-inch-square
patch of tissue in the uppermost part of the nasal
passages.
• olfactory cells are covered in mucus
• which dissolve volatile molecules and stimulate the
cells
• the cells trigger nerve impulses that travel to the
brain
• which interprets the impulses as different smells
CHEMICAL SENSES (CONT.)
• Smell, or olfaction
– Sensations and memories
• nerve impulses travel to the olfactory bulb
• impulses are relayed to the primary olfactory
cortex
• cortex transforms nerve impulses into olfactory
sensations
• can identify as many as 10,000 different odors
• we stop smelling our deodorants or perfumes
because of decreased responding
• called adaptation
CHEMICAL SENSES (CONT.)
• Smell, or olfaction
– Functions of olfaction
• one function: to intensify the taste of food
• second function: to warn of potentially dangerous
foods
• third function: elicit strong memories; emotional
feelings
TOUCH
• Touch
– includes pressure, temperature, and pain
TOUCH (CONT.)
TOUCH (CONT.)
• Receptors in the skin
– skin
– hair receptors
– free nerve endings
– Pacinian corpuscle
TOUCH (CONT.)
• Skin
– outermost layer
– thin film of dead cells containing no receptors
– just below, are first receptors which look like groups
of threadlike extensions
– middle and fatty layer
– variety of receptors with different shapes and
functions
– some are hair receptors
TOUCH (CONT.)
• Hair receptors
– free nerve endings wrapped around the base of each
hair follicle
– hair follicles fire with a burst of activity when first bent
– if hair remains bent for a period of time, the receptors
will cease firing
– sensory adaptation
– example: wearing a watch
TOUCH (CONT.)
• Free nerve endings
– near bottom of the outer layer of skin
– have nothing protecting or surrounding them
• Pacinian corpuscle
– in fatty layer of skin
– largest touch sensor
– highly sensitive to touch
– responds to vibration and adapts very quickly
TOUCH (CONT.)
• Brain areas
– somatosensory cortex
– located in the parietal lobe
– transforms nerve impulses into sensations of touch
temperature, and pain
PAIN
• What causes pain?
– pain: unpleasant sensory and emotional experience
that may result from tissue damage, one’s thoughts or
beliefs, or environmental stressors
– pain results from many different stimuli
PAIN (CONT.)
PAIN (CONT.)
• How does the mind stop pain?
– gate control theory of pain
– nonpainful nerve impulses compete with pain
impulses in trying to reach the brain
– creates a bottleneck or neutral gate
– shifting attention or rubbing an injured area decreases
the passage of painful impulses
– result: pain is dulled
PAIN (CONT.)
• Endorphins
– chemicals produced by the brain and secreted in
response to injury or severe physical or psychological
stress
– pain reducing properties of endorphins are similar to
those of morphine
– brain produces endorphins in situations that evoke
great fear, anxiety, stress or bodily injury as well as
intense aerobic activity
PAIN (CONT.)
• Dread
– connected to pain centers in brain
– not the act itself that people fear
– time waiting before event causes dread
• Acupuncture
– trained practitioners insert thin needles into various
points on the body’s surface and then manually twirls
or electrically stimulates the needles
– after 10-20 minutes of stimulation, patients often
report a reduction in various kinds of pain