Unit IV Sensation and Perception Modules: 16-21
Module 16 Basic Principles
Module 17 Influences on Perception
Module 18 Vision
Module 19 Visual Organization + interpretation
Module 20 Hearing
Module 21 Other Sensation
Introduction:
Prosopagnosia- face blindness
Right hemisphere facial recognition
Example: frogs have cells in their eyesà that respond to small, dark moving objects
Silk Worm sense pheromones of other silk worms.
Human ears are sensitive to human voices especially- baby crying
Module 16 Basic Principles of Sensation and Perception
Sensation
Detect information: “The process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment.”
Perception
Process by which the brain organizes and interprets sensory input.
Sensory/perception is a continuous process and blended.
(Gestalt concepts)
Pg. 152
Bottom -up Processing
Starts at the sensory receptors and works up to higher levels of processing.
Lines
Angles
Colors
We interpret these building blocks from the specific to the whole. The parts make up a picture.
Top Down Processing:
Constructs perceptions from sensory input by drawing on our experience and expectations.
Taking the whole, analyzing the whole into parts.
Pg. 153
Selective Attention:
Your focus on a small bit of sensory information at a time.
Selective Attention and Accidents:
Blinking-people who blink more are less focused
23xs more risk of accident when texting.
Pg. 154
Selective Inattention:
Inattentioinal Blindness:
Failing to see information or stimuli
When you are focused on other things.
Change Blindness- Failure to notice changes
Pop out-some things automatically bring more attention
Pg. 155
Transduction
The process of converting energy (stimuli) into nerve impulse
Receive sensory stimulation
Transform stimuli to normal impulse
Deliver neural info to our brain
Seeing, hearing, feeling pain, taste, and smell all use transduction.
Psycho-Physics (lots of energy is all around us)
Thresholds:
Fechner, Gustav- studied sensation of stimuli
Foundà Absolute Thresholds
The minimum stimulation necessary to detect a particular light, sound, pressure, taste, odor – 50% of the time.
Detecting a Weak Stimulus depends on:
Signal strength
Experience
Expectation
Motivation
Alertness
Signal Detection Theory:
Predicts when we will detect weak signals
Subliminal – below your absolute threshold
Priming- we can evaluate stimulus even when we are not aware of it. “the activation, often unconsciously, of certain associations, thus predisposing one’s perception, memory, or response.
Complex mental operation- Only when the stimulus triggers synchronized activity in several brain areas does it reach consciousness.
Difference Thresholds:
JND = Just Noticeable Difference
“Is the minimal difference a person can detect between any two stimuli.”
The difference threshold increases with the size of stimulus.
Weber’s Law:
States, for a person to perceive a difference in stimuli; the stimuli must differ by a constant minimum percentage.
Thinking Critically: Can Subliminal Messages control our behavior?
Answer: Priming does work by creating an expectancy
Pg. 159
Sensory Adaptation:
Exposure to unchanging stimuli we become accustomed to the stimuli
It has less effect
Reduces sensitivity
Sensory receptors are alert to novelty
They get bored with repetition
Free our attention
We are sensitive to changing stimuli
Module 17 Influences on Perception Pg. 163-170
Influences on Perception
Perceptual Set:
Expectations are created by experience
(stereotypes)
“A set of mental tendencies and assumptions that affect what we perceive.”
Context Effects
Also creates an expectation
And experience influences perception
Pg. 166
Emotion and Motivation
Top down processing impacts our emotions (the overall mood of a situation) sad music makes us sad…
Stimuli impacts emotions
Perceptions are influenced by our own emotion
When we are affected by emotions we can perceive things differently
Or
Motivation affects ambiguous images.
Emotions influence social perception of reality
Example “Love of a Spouse”
Critical Thinking Pg. 167-69
ESP-Para-psychology
Telepathy
Clairvoyance
Pre-cognition
Module 18 Vision Pg. 176-181
The Stimulus Input
Light Energy
Visual Stimuli Is Energy
Electromagnetic
Waves
Wavelength – “the distance from one wave peak to the next”
Determines Hue = color
Intensity = the amount of energy = amplitude or height= brightness
Figure 18.2 Page 172
See the list of light waves…
The Eye:
Cornea
Pupil
Iris
Lens
Retina
Accommodation:
Pupil- opening
Iris- is the color, dilates, constricts amorous
Lens- behind the pupil, focuses light rays on the retina
Accommodation- changing the curvature of the lens
Kepler
Inverted Image
The Retina: Pg. 172
Receptor cells
Convert particles of light energy into neural impulses
Rods- receptor cells
Bi-polar cells
Ganglion cells
Optic nerve- send neural impulse to brain
1 million messages
1 million ganglion fibers
Blind spot
Fovea= cones
Cones:
Fovea
Fine detail
Color
Transmit one single bi-polar cell dedicated to cones
Rods:
Share bi-polar cells
Black and white
Motion
Peripheral vision
Dark
More Rods than Cones
Eyeball Chart pg. 172
Pg. 174 Copy Chart on Table 18.1
Adaptation
Habituation
“Dark Theater”
Feature Detectors
Occipital lobe
Visual Cortex
Firm Retina
Feature Detectors
Cells respond to specific features
Edges
Lines
Angles
Movement
Pg. 176
How is the brain organized for specific visual tasks?
Parallel Processing
Doing many things at once
Motion, form, depth, color(all simultaneously)
30% of cortex
Color Vision Theories:
Color blindness- (lack of red or green cones)
1 person in 50
Mostly males
Genetic connection
Helmholtz + Young
Light waves of 3 primary colors
Red+Green+Blue
Trichromatic Theory:
Receptors
3 types in retina
Each sensitive to 1 of 3 colors
Red – Green – Blue
Yellow = red + green cones
Color Blind= dichromatic (dogs) or Monochromatic
Hering & After Image
- Red vs. Green
- Blue vs. yellow
- White and black
Pg. 179
Opponent Process Theory
After Image = opponent Process Theory
Opposing retinal processes
Some cells are stimulated by green and inhibited by red others à stimulated by red and inhibited by green
Module 19 Visual Organization and Interpretation
Visual Organization = Perceptual Organization
Gestalt:
Process of organizing visual information to form a whole picture.
Gestalt Tendency:
The brain has tendency to make sense of stimuli, automatically
“The whole is greater than the sum of its parts.”
Necker Cube:
Visual Stimuli
Lines
The brain automatically organizes stimuli in meaningful shapes.
àAmbiguous stimuli
Basically the brain interprets stimuli to find patterns.
Discrimination of stimuli- brain sorts it and determines meaning.
Pg. 183
Form Perception
Figure Ground, Proximity, Grouping, Continuity, Closure
Figure Ground
Perception of an object must be distinct from its surroundings
Really about distinguishing stimuli
Pg. 184
Depth Perception
3 dimensional vision
Uses depth perception to estimate/understand distance
Is partly innate ability
Is partly learned
Visual Cliff experiment proved innate depth perception
Binocular Cues
We see 3 dimensionally = depth because we have 2 eyes = Retinal Disparity
Retinal Disparity:
The fact each eye see’s slightly different images
Linear Perspective
Light and Shadow
3-D Movies
2 cameras
Simulate retinal disparity
Glasses allow only vision for the left camera and the right camera
Carnivores vs. Herbivores and Depth perception.
Carnivores have good convergence eyes in front of face and herbivores, eyes on side of head, have good peripheral vision
Monocular Cues:
Depth cues available to each eye separately
Each of the following can be interpreted with only eye:
Relative Height
Relative Motion
Relative Size
Interposition
Perceptual Constancy
“Comparisons govern our perceptions”
We naturally perceive objects as unchanging à even though the objects context may change.
It works both ways-
1. Objects appear to change based on context.
2. We know objects don’t change.
“The object as it is perceived and the object as it actually exists.”
Also perceptual constancy
Assumptions and expectancy matter
Light effects perception of color
Size perception is altered by context (pg. 188)
Shape and size constancy
Objects seen to change with angle of view
Pg. 189
Moon Illusion- the juxtaposition of the moon indicate a different size constancy
Ames Room- different angles and contexts of the room skew our perception of the room.
Pg.190
Visual Interpretation
1. Deals with learned perceptions
2. Perceptual Adaptation
Module 20 Hearing Pg. 194-201
Audition = hearing
Sound waves
Frequencies
Pg. 195
Stimulus Input
· Sound waves
· Air pressure is detected
· Feel vibrations
Frequency is the length which determines the pitch
Long waves = lower frequency and low pitch
Short waves = high frequency and high pitch
Amplitude of waves =loudness
Sound is measured in decibels
Zero decibels = Absolute Threshold
10 decibels = corresponds to 10 fold increase in intensity
Pg. 195
The Ear
Outer Ear
Ear Drum
Vibration
Middle Ear
Hammer, Anvil, Stirrup, Cochlea, Hair Cells, Auditory Nerve
Pg. 196 “Draw the Middle Ear”
Hair Cells- “quivering bundles that let us hear extremely sensitive and extreme speed.”
Cochlea
16000 hair cells trigger a neural response.
Pg. 197
Sensorineural Hearing Loss = Nerve Deafness
Over 1000 decibels = hearing loss
Conduction Hearing Loss:
Caused by damage to mechanical aspects of hearing = the bones in the ear
Ringing Ears= damage
Cochlea Implant:
Aids nerve deafness
“Translates sounds into electrical signals that, wired into the cochlea’s nerves,…”
188,000 people use them.
Perceiving Loudness:
The number of hair cells that are activated relates to how loud a sound is heard.
Perceiving Pitch:
Low or high frequencies
Theories of Audition:
Helmholtz Place Theory:
Different pitches are different waves of sound
Waves trigger different places in the cochlea.
Different places on the cochlea respond to different frequencies.
(low pitched sound doesn’t fit, not so accurate in low frequencies)
Frequency Theory:
Cells respond to specific frequencies
“Neural impulses to the brain at the same rate as the sound waves.”
Frequency of 100 waves per second = 100 pulses per second that travel up the auditory nerve.
(Addresses low frequencies)
Module 21 Other Senses Pg. 202-213
4 other senses:
Touch
Taste
Smell
Body Position
Touch:
Important for devleoment
Nurturing + biological development
Psychological development needs touch from mother is really important
Adults need human contact
Sense of Touch
Distinct skin senses
Pressure
Warmth
Cold
Pain
Lots of sensitivity in different parts of the body
Body responds more to unexpected stimulation
Pain:
Body’s way of telling you of injury
Forces you to change your behavior
Some people don’t feel pain
Hereditary Sensory and Autonomic Neuropathy
Chronic Pain is more prevalent
Understanding Pain
Women are more pain sensitive than men
Individual Pain Sensitivity Varies by
· Genes
· Physiology
· Experience
· Attention
· Culture
Biological Influences to Pain:
Nociceptors = sensory receptors that detect hurtful:
Temperature
Pressure
Pain
Gate Control Theory
Spinal Cord
1. Has small nerve fibers that conduct most pain signals
2. Large Fibers that conduct most sensory signals.
Spinal Cord has gates
When tissue is injured the small fibers activate = open a gate = pain
Large fibers close the gate & block the small fibers = Preventing pain sensations
Treating Chronic Pain
Stimulate “gate closing” activity in the large neural fibers
Message
Electrical stimulation
P 204
Factors to Pain Experience (Psychological)
1. Interpretation of Pain (cognitive)
- Distractions reduce intensity of pain
2. Endorphins (bio)
Phantom Limb Pain (Ramachandran @ 9 minutes)
Brain misinterprets the spontaneous CNS activity
7 of 10 amputees experience pain or movement in a non-existent limb…
Psychological Influence of Pain
Distraction
Memory processing
è Recall 2 things
è 1. Memory peak moment of pain
è 2. The pain they felt at the end
Perception of Pain:
Varies with situation
We experience more pain when others seem to experience pain
Empathy for another’s pain may create pain response in the brain.
Expectations create less pain response
Controlling Pain
Psychosomatic
“Believing becomes reality”
Placebos can reduce pain experience
Distraction
Pleasant Images
Changing attention away from painful stimulation
Reduces pain related activity in brain
“Diverting the brains attention may bring relief.”
Taste:
Sweet
Salty
Sour
Bitter
Umami= meaty taste/MSG
Evolutionary Explanation
Tastes enable survival
Protein = energy
Aversive conditioning = toxic tastes
Tastes can be learned
Taste is a chemical sense
Taste Buds:
200 or more
Each bud has 50-100 taste receptors (hair like)
Receptors are specific to tastes
Brain, temporal lobe
Older people lose taste, # of taste buds decrease
Taste sensitivity declines
Smoking accelerates the decline
Smell= Olfaction
Anosmia- people unable to smell.
Chemical Sense- molecules in air
20 million receptors
10,000 odors
Attractiveness of smells = learned
Connection Odor + Emotion
Connection Odor + Memory-à limbic system
Pg. 209
Body Position and Movement:
Kinesthesia- the sense of position and movement
Vestibular Sense:
Monitors head position and movement
Also you body
Sense of body movement
Semi-Circular Canals
Contain fluid that moves when your head rotates or tilts
Receptors send message to cerebellum = sensation of body movement and balance