Transcript Learning - Dimensions Family Therapy

Sensation
&
Perception
Sensation & Perception
• Sensation
– Recognition that something is there
– Something triggers the a dendrite of the first
neuron
• Perception
– Interpretation of a sensation
– What is it that I am hearing, seeing, etc.
3 Key Principles
• There is no 1-1 correspondence between physical and
psychological reality
– Alternative perceptions of any given sensation
– Yellow traffic light
• Sensation and perception are active processes
– We focus on stimuli that are relevant to ourselves
– Phenomenological world
• Joint product of external reality and one’s creative efforts to
understand reality
• Sensation and perception are adaptive
– We adapt to our environment
Sensing the Environment
• Sensory receptors
– Specialized cells that transform energy (stimuli)
into neural impulses that can then be interpreted
by the brain
• Transduction
– Converting a sensation into an internal
electrical signal to convey to the CNS
Absolute Thresholds
• Absolute Threshold
– Amount of energy needed for someone to
notice a stimulus
– Detect stimulus 50% of the time
– Varies from person to person
– Varies over one’s life span
Signal Detection Theory
• Sensitivity
– How well one picks up a given stimulus
• Response Bias
– One’s readiness to report detecting a stimulus
when uncertain
• False alarm- Report a signal when not there
• Hit- Accurately reporting a signal
• Correct False- Accurately reporting no signal
Difference Thresholds
• Just noticeable difference (jnd)
– The lowest level of stimulation needed for one
to detect a change in a stimulus’ signal or a
difference between two signals
• The level of the original signal is key to
detecting just noticeable differences
Weber’s Law
• The greater the original signal the greater the
difference necessary to achieve a difference
threshold
• A math equation used to calculate just noticeable
differences
• For weight Weber’s fraction is 1/50
– 50 pound bag= Add 1 pound to achieve jnd
– 100 pound bag= Add 2 pounds to achieve jnd
Fechner’s Law
• Relationship between intensity one reports a
sensation is related to the amount of the original
signal
• Suggests that all just noticeable differences are
created equal
– Each additional jnd feels like one incremental unit in
intensity
• Logarithmic relations between subjective and
objective stimulus
Steven’s Power Law
• As the perceived intensity of a stimulus
grows arithmetically, the actual magnitude
of the stimulus grows exponentially
Sensory Adaptation
• Our propensity to quickly adjust to a
stimulus level
– Walk into a dark theater
– Adapt to a high sound level in a sports stadium
• Prevents sensory overload
Vision
• Light is detected by the retina
– Cornea
– Pupil
– Lens
• Retina transduces light into electrical signal
– Photoreceptors
• Rods= black and white
• Cones= color
– Optic Nerve
– Receptive fields
Vision
• Optic Nerve sends information on two pathways
– Superior Colliculus in the midbrain
– Lateral geniculate nucleus in the thalamus and then
onto the visual cortex
• Visual Cortex
– Feature detectors
• Only discharge when a stimuli matches a given pattern
– What pathway
• Jut what is an object
– Where pathway
• Where is the object located in space
Color
• Trichromatic Theory
– The eye has three type of receptors for
• red
• green
• blue
• Opponent-process theory
– Three antagonistic color systems
• Blue-yellow
• Red-green
• Black-white
Audition
• Sound involves vibrations in the air from
the source (sound waves)
• Sounds travel much slower than light
– See lightning
– Hear thunder seconds later
• Sound can travel through objects
Sound Waves
• Frequency (pitch)
– Number of times particles oscillate per second
– Timber is the combination of oscillations for a
given sound source
• Amplitude (loudness)
– Height and depth of sound waves
The Ear
• Auditory Canal
– Sound waves enter the ear through the auditory canal to
the eardrum
• Eardrum
– The eardrum’s stirrup creates pressure in the fluid of the
cochlea
• Cochlea
– Hair cells attached to the basilar membrane trandsduce
sound & fire sensory neurons in the auditory nerve
Two theories on sound
• Place theory
– Different areas of the basilar membrane
respond to different frequencies
• Frequency theory
– Rate of vibration of the basilar membrane
transforms frequency into pitch
Sound Localization
• Involves the identification of the location of
a sound in space
• Binaural neurons that respond to relative
differences in the loudness and timing of
sensory signals transduced by the two ears
Olfaction (Smell)
• Enables us to detect both pleasant and
potentially dangerous odors
– Spoiled food
• Smell can take place through your nose and
your mouth
• We smell gas molecules in the air
Olfaction
• Olfactory Nerve
– Composed of axons from hundreds of different
olfactory receptors
• Olfactory Bulbs
– Receive signals from the olfactory nerve and
transmits to the olfactory cortex in the brains’
frontal lobes
Taste
• Taste buds transduce chemical input from
molecules and send them to the medulla and pons
in the hindbrain and then on two pathways
• Primary Gustatory cortex
– Identification of tastes
• Limbic system
– Generates gut level reactions and learned responses to
tastes
Gustatory Systems Four Tastes
•
•
•
•
Sweet
Sour
Salty
Bitter
Touch
• We have approximately 18 square feet of skin
• We have approximately 5,000,000 touch receptors
• Touch involves three senses:
– Pressure
– Temperature
– Pain
Pressure & Temperature
• Pressure involves the displacement of skin
– Varies widely across different parts of the body
– Very sensitive on fingertips
• Pin prick hurts
– Little sensitivity on the buttocks
• Large needle hurts less than pin prick on the finger
• Temperature
– Difference between skin temperature and the
corresponding temperature on an object is the key
Pain
• Pain
–
–
–
–
–
Purpose of pain is to limit tissue damage
Varies by individual
No specific physical stimulus
Skin does not transduce pain waves
Free nerve endings transmit signals to the brain when a cell is damaged
• Experiencing Pain
– Impacted by beliefs, expectations and emotional state
– Anxiety can increase pain
– Intense fear, stress, or concentrating on other things can inhibit pain
• Controlling pain
– Organic source
– Mental attitude
Proprioceptive Senses
• Regulate body position and movement
• Vestibular Sense
– Provides information on the position of the
body by sensing gravity and movement
• Kinesthesia
– Provides information about the movement and
position of the limbs and other body parts
relative to one another
Perception
• Involves the organization and interpretation
of sensations
• Organizes sensations into meaningful units
• Interpretation of the organized sensations
– What does it mean
Perceptual Organization
• Integrate sensations into percepts
– Meaningful perceptual units
– Locates percepts in space
– Preserves percepts meaning while analyzing
them
• Form Perception
– Organizing sensations into meaningful shapes
and patterns
Phantom Limbs
• Damage to sensory systems leads to
reorganization of those systems
• Phantom limbs involve people who have
lost an arm or a leg sensing its presence
• Amputees experience phantom limbs for
some time after surgery
Gestalt Principles of
Perceptual Organization
• The German term Gestalt means “whole” or
“form”
• Key is that the whole is greater than its parts
Figure- Ground
• Figure= Object they
are viewing
• Ground= Background
the object is embedded
within
• Insert commercial
example here
Similarity
• We tend to group
similar elements
together
Proximity
• We tend to group
together objects that
are close to one
another
Good Continuation
• We organize stimuli
into continuous lines
or patters
Simplicity
• We tend to perceive
the simplest pattern
possible
Closure
• We tend to perceive
incomplete figures as
complete
Perceptual Illusions
• The brain’s efforts to
organize sensations
into coherent percepts
fails
• Organization lead to
perceptual
misinterpretations
Depth Perception
• Binocular Cues
– Visual input integrated from both eyes
• Monocular Cues
– Visual input from one eye
Binocular Cues
• Retinal disparity
– Results from our eyes being in slightly different locations on our
face
• Retinal disparity enables depth perception
• Binocular cells
– Located in the primary visual cortex, some of these cells respond
more vigorously when the same input arrives from each eye
– Other binocular cells respond to the disparity between the eyes
Binocular Cues
• Convergence
– When you observe an object close to you your
eyes come together (converge)
– When you observe more distant objects your
eyes diverge
Monocular Cues
• Interposition
– When one object obstructs
another the blocked object
is perceived as more distant
• Elevation
– Objects farther away are
higher on one’s plane of
view and thus appear higher
up toward the horizon
Monocular Cues
• Texture Gradient
– Textured surfaces
appear coarser at close
range and finer/more
densely packed at
greater distance
• Linear Perspective
– Parallel lines appear to
converge in the
distance
Monocular Cues
• Shading
– The brain assumes light comes from above. Thus, we
interpret shading differently toward the top versus the
bottom of an object
• Aerial Perspective
– Distant objects appear fuzzier than closer ones
• Familiar Size
– We assume an object is its usual size even though it
appears smaller as distance increases
Monocular Cues
• Relative Size
– When we look at two objects known to be of
similar size, we perceive the smaller object as
farther away
• Movement
– When we move images of closer objects sweep
across our field of vision faster than objects
more distant
Motion Perception
• Involves multiple sensory modes
– Vision
– Sound
• Two systems for processing movement
– Motion of the object being observed
• Football wide receiver
– Motion of the person doing the observing
• Quarterback
Perceptual Constancy
• Color constancy
– We perceive objects (apple) as the same color
regardless on changes in illumination
• Shape Constancy
– We perceive objects as the same shape regardless of
sensory input (position or angel)
• Size Constancy
– Objects remain the same size regardless of distance
from the object such as a bridge on the highway
Perceptual Interpretation
• Involves generating meaning from sensory
experience
• Influenced by experience
• Gibson’s Theory of Direct Perception
– Meaning is immediate and obvious
– Adaptive in nature
Perceptual Interpretation
• Bottom-up
– Perception begins with multiple sensations and then
integrate the data in higher regions of the brain
– Inductive process
• Top-down
– Perception begins at higher regions of the brain based
on past experience as soon as sensations begin coming
in
– Deductive process
Perceptual Expectations
• Perceptual Set
– We anticipate what we will perceive before any sensory data
received
• Context
– We anticipate what we expect to perceive in a given situation
• People make passes in bars
– Was a comment a pass or just being polite?
• Schemas
– Schemas are patterns of thinking about something that enables us
to have a sense of predictability
• Dogs bark, cats don’t bark
Motivated Perception
• We tend to perceive what we want to
perceive