Download Unit V - Sensation and Perception

Unit V - Sensation and Perception
Module 16: Basic Principles of Sensation and Perception
Sensation
● Sensation: sensory receptors and and the nervous system receive and recognizing the
world around us
● Perception: interpreting sensory information by making it memorable
● Processing
○ Bottom-up: not based on past experiences, interprets by taking sensory
information and works to higher levels of understanding
○ Top-down: makes assumptions on recent sensory input from past experiences
● Selective attention: choosing which stimulus to pay attention to, conscious
○ Cocktail party effect: a person’s ability to listen to one voice among a crowd
Selective Inattention
● Inattentional blindness: blind to all but one stimuli
○ Ex. Focusing so much on the number of times a ball is based you miss seeing the
bunny in the background
● Change Blindness: miss changes in front of your face
○ Ex. Not noticing the person at the front desk changes when they reach down for
a pen
● Choice Blindness: making your decision based on predispositions
○ Ex. More likely to think something tastes more sour if the label says so
● Transduction: transforming one form of energy to another
○ Receive sensory stimulation, transform stimulation, deliver neural info to brain
Thresholds
● Absolute threshold: the minimum stimulation in order to detect a particular stimulus
○ Ex. Vision: you can see a flame of a candle 30 miles away on a dark clear night
half the time
● Signal detection theory: predicts when and how and when we can detect stimuli
○ Subliminal: is below the absolute threshold which means we are not consciously
aware of certain stimuli
○ Prime: making certain associations based on memory, unconscious
■ Ex. Associating an image as negative or positive triggers emotion
● Difference threshold: the noticeable difference in order to detect a change in a stimuli
○ Weber’s Law: two stimuli must differ by a certain percentage to be detected
■ Ex. Vision: 2 lights must differ by 8%
Sensory Adaptation
● Sensory adaptation: decrease in noticing a certain stimuli over time
Module 17: Influences on Perception
● Perceptual set: the set of mental tendencies and assumptions that affect our perception
○ Top-down
● Context Effects: based on context or location can cause the same stimulus to be
perceived differently
○ Ex. “Eel is on a wagon” -eel=wheel “eel on an orange” -eel=peel
● Emotion and Motivation: different stimuli can bring up particular emotions altering your
perception through top-down processing
○ Ex. Sad music can make you perceive the word morning as mourning
Module 18: Vision
● Wavelength: Distance from one wave to the other
● Hue: Color we experience
● Intensity: Amount of energy in light waves
● Accommodation: Len focus’ on light rays by changing curvature
The Eye (In order)
● Cornea: Where light enters and bends it, also protects the eye
● Pupil: Small adjustable opening and light passes through
● Iris: Colored muscle that controls pupil. Dilates or constricts light intensity
● Lens: Behind pupil that focus’ the incoming light
● Retina: Multilayer tissue
The Retina
● Light triggers chemical changes or neural signals that then activate bipolar
cells which activates the ganglion cells which lead to the optic nerve
● Rods: Receptor cells for more of our peripheral vision that detects mainly
black and white
● Cones: Receptor cells that better detect vision and more precise vision.
Better with color.
● Optic Nerve: Ganglion cells axon intertwined. Sends nearly 1 million
messages at once.
● Blind Spot: No receptor cells where optic nerve leaves eye
● Fovea: Retina’s central focus
Visual Info Processing
● Begins in the retina and passes on electrical impulses and encode the
sensory info.
● Info then goes to bipolar cells then right to ganglion cells straight to the
optic nerve. Optic nerve goes to the occipital lobe.
*Same sensitivity can lead cells to misfire, also responsive to pressure that the
brain interprets as light
● Feature Detection: Specialized neurons that receive info from individual
ganglion cells in retina. If damaged, might not recognize familiar faces.
● Parallel Processing: Encoding many things simultaneously. Analyzing visual
scenes, brain divides the into subdimensions. Motion, Form, Depth, and
Color.
● Grandmother cells: Selective to 1 or 2 faces in 100. Facial recognition
requires 30% of cortex.
Color Vision
● Difference threshold is very low, it can discriminate more than 1 million
color variations.
● Young - Helmholtz Trichromatic Theory: Color can be created by combining
light waves of 3 primary color (red, green, blue)
● Color Deficient Vision (colorblind): Lack of red/green sensitive cones
● Opponent Process Theory: Red/Green, Yellow/Blue, White/Black
Module 19: Visual Organization and Interpretation
Visual Organization
● Gestalt psychologists emphasized our tendency to integrate pieces of
information into meaningful wholes
● Figure-ground: in the eye-brain system, the first perceptual task is to
perceive any object as distinct from its surroundings
● Grouping: the perceptual tendency to organize stimuli into coherent groups
● Proximity: we group nearby figures together
● Continuity: we perceive smooth, continuous patterns rather than
discontinuous ones
● Closure; we fill in gaps to create a complete, whole, object
Depth Perception
● Depth perception: the ability to see objects in 3 dimensions although the
images that strike the retina are 2 dimensional. This allows us to judge
distance
● Visual cliff: a lab device for testing depth perception in infants and young
animals. This model was created by Gibson and Walk.
● Biology predisposes us to be wary of heights
Binocular Cues
● Binocular cues: depth cues, such as retinal disparity that depend on the use
of 2 eyes
● Our 2 eyes perceive slightly different images of the world because eyes are
2.5 inches apart
● Retinal disparity: a binocular cue for perceiving depth: by comparing images
from the retinas in the 2 eyes, the brain computes distance. The greater the
difference between the 2 images, the closer the object seems to appear
● Monocular cues: depth cues, such as interposition and linear perspective,
available to either eye alone
Motion Perception
● The brain computes motion based on its assumption that shrinking objects
are retreating (not getting smaller) and enlarging objects are approaching
● Stroboscopic movement: the brain perceives continuous movement in a
rapid series of slightly varying images
● Phi phenomenon: an illusion of movement created when 2 or more
adjacent lights blink on and off in quick succession.
Perceptual Constancy
● Perceptual constancy is when you perceive objects as unchanging (having
consistent shapes, size, brightness, and color) even as illumination and
retinal images change
Color and Brightness Constancy
● Our experience of color depends on the object’s context
● Color constancy: perceiving familiar objects as having consistent color, even
if changing illumination
● We can see color from the brain’s computation of the light reflected by an
object relative to the object surroundings it
● Brightness constancy: depends on the context; we perceive an object as
having a constant brightness even while its illumination varies
● Relative luminance: the amount of light an object reflects relative to its
surrounding
● Surroundings govern our perceptions
Shape and Size Constancies
● Shape constancy: we perceive the form of familiar objects as constant even
while our retinas receive changing images of them
● Visual cortex neurons rapidly learn to associate different views of an object
● Size constancy: we perceive objects as having a constant size even while
our distance from them varies
● Perception is not merely a projection of the world onto our brains. Rather,
our sensations are disambled into information bits that our brain, using
both bottom-up and top-down processing, then reassembles into its own
functional model of the external world
● Our brain constructs perceptions
Visual Interpretation
● Kant - knowledge comes from inborn ways of organizing sensory
experiences
● Locke - we learn to perceive through experience
● There is a critical period for normal sensory and perceptual development
Perceptual Adaptation
● In vision, the ability to adjust to an artificially displaced or even invented
visual field is known as perceptual adaptation.
Module 20: Hearing
● Highly adaptive
Sound Waves
● Their amplitude determines their loudness
● Length of frequency determines the pitch experienced (ex: long waves
have low frequency, low pitch and short waves have high frequency, high
pitch)
● Measured in decibels ( 0 decibels is the absolute threshold for hearing)
The Ear
● Chain reaction begins at outer ear channeling waves through auditory canal
to eardrum, a tight membrane where it begins to vibrate
● Middle Ear picks up on vibrations- transmit them to cochlea- cochlea
membrane vibrate- jostling fluid that fills the tube- causing ripples in basilar
membrane bending hair cells
● Hair cell movements triggers impulses in nerve cells - causes axon of cells
converge to form auditory nerve which sends neural messages to auditory
cortex in temporal lobe
● Damage to hair cells can rebound fast unless there's long exposure - 85+
decibels can cause damage
Perceiving Loudness
● Brain interrupts loudness from number of active hair cells
● Hair cells lose sensitivity to soft sounds
● Hearing loss people like sound compressed- harder to hear sounds are
amplified more than loud sounds
● Great Amplitude- bright colors, loud sounds
● Small Amplitude- dull colors, small sound
Perceiving Pitch: Two Theories
● Helmholtz's Place Theory- Believed different sound waves trigger activity at
different places along basilar membrane. Believed brain determines sounds
pitch by recognizing specific places that generate neural signals
➔ Explains how we hear high pitch but not low
➔ Proven to be false
● Frequency Theory- Believed brain reads pitch by monitoring frequency of
neural impulses traveling up auditory nerve. Believed membrane vibrates
with incoming sound waves triggering neural impulses to brain same route
as sound wave
➔ Proven false, an individual neuron cannot fire faster than 1000 times per
sec so there's no way we sense sounds with frequency above 1,000 waves
per sec
● The Valley Principle is most likely true- neural cells can alternate firing in
rapid succession achieving a combined frequency above 1000 waves per
sec
Locating Sounds
● Intensity difference and time lag between ears is small (0.000027 sec)
Module 21: The Other Senses
Touch
● Sense of touch is a mix of skin senses for pressure, warmth/cold, and pain
● Tickle: Stroking adjacent pressure spots
● Itch: Repeated gentle stroking of a pain spot
● Wetness: Touching adjacent cold and pressure spots. Ex. touching dry, cold
metal
Pain
● Body’s way of telling you something has gone wrong
● Chronic pain is an alarm that won’t shut off
● Understanding it:Pain differs from individual. Reflects both Bottom up and
Top-down processing
● Biology influence have different nocicepters which are sensory receptors
that detect temperature, pressure, and chemicals.
● Gate Control Theory: Spinal cord contains neurological “gate” which tissue
is injured, small fibers activate and open gate. When you feel pain, large
fibers closes gate and blocks pain signals from brain
● When distracted from pain and endorphins are flowing, the experience of
pain diminishes
● People that have a gene that provide more endorphins are less bothered by
pain and the brain is less responsive
● Other people have a mutated gene that disrupts pain circuit
neurotransmission and experience little pain
● Phantom Limb Sensations: Brain can create pain that misinterprets central
nervous system actively in an absence of normal sensory input
● Non Threatening Hallucinations: People with eyesight loss
● Psychological Influences: Focusing on winning game, so you may through
pain
● Social-Cultural Influences: Tend to perceive pain when others experience
pain
● Controlling pain: Drugs, surgery, acupuncture, electrical stimulation
messages, exercise, hypnosis, relaxation training, thought distraction, and
placebo may help.
Taste
● Purpose: Encourage us to provide energy and detect harmful substances.
● Salty, sweet, sour, bitter, and umami
● Spicy is pain on the tongue
● Taste is a chemical sense
● 200 plus taste buds for each bump: Pores catch food chemicals and each
pore has about 50-100 receptor cells that have hair to sense food
molecules
● Tastes buds reproduce every week or two, diminishes as you get older
Smell
● One of the oldest senses
● Molecules of the substance reach a cluster of about 20 million receptor
cells in the nasal cavity
● Olfactory Receptor cells: Wave like sea anemones that respond selectively
● When smelling something it instantly alerts the brain through axon fibers
because the olfactory neurons bypass the thalamus
● Odor molecules come in different shapes and sizes
● 350 receptor proteins are embedded in the nasal cavity neurons
● 10,000 odors we can detect as humans
Body Position and Movement
● Kinesthesia: sense of a position and movement of body parts
● Vestibular sense: monitors head’s position and movement. In the inner ear
there are vestibular sacs filled with fluid
Sensory Interaction
● This means that one sense may influence another
● Embodied Cognition: Brain processing bodily sensations.