Chapter 4 Sensation & Perception &
Chapter 5 States of Consciousness
“All knowledge has its origins in our
perceptions.” – Leonardo Da Vinci
Vision
Hearing
Smell
Taste
Touch
Introductory Questions
1. Why is it that a pencil appears to bend when it is into a glass of water?
2. Why does the world look rightside up when the lens of the stuck eye
makes the retinal image upside down?
3. Why does the moon look bigger when it is low in the sky, near the
horizon, than when it is high in the sky, near the zenith?
4. How far can you see?
5. Why are so few textbooks or newspapers printed with yellow ink on
white paper?
6. Given that our eyes sometimes play tricks on us, how can we be sure
that the ‘real world’ out there really exists?
Definitions
• Sensation
• process of detecting, converting, and
transmitting raw sensory information
from the external and internal
environments to the brain
Sense
organs:
eyes, ears,
nose, tongue,
skin, & internal
body organs
• Perception
• process of selecting, organizing and
interpreting sensory information
• enables us to recognize meaningful
objects and events
Happens in
the brain!
Sensation
• Bottom-Up Processing
Ex: you have
• Information processing beginning “at the bottom”
ingredients and
with raw sensory data that are sent “up” to the
must put them
brain for higher level analysis
together to make
• Data driven processing that moves from the parts to something edible
the whole
• Top-Down Processing
• Information processing starting “at the top” with
higher level cognitive processes (such as
expectations and knowledge) and then “working
down”
• Conceptually driven processing that moves from the
whole to the parts
Ex: you have
ingredients and
a recipe &
picture of a
completed cake
and you must
recreate the
cake
Sensation- Thresholds
• Absolute Threshold
– minimum stimulation needed to detect a particular
stimulus
– usually defined as the stimulus needed for
detection 50% of the time
• Difference Threshold
– minimum difference between two stimuli that a
subject can detect 50% of the time
– just noticeable difference (JND)
– increases with magnitude
Easier to tell the difference
between 4 & 5Hz than
1000 & 1001Hz
Ex: listen to
headphones
and indicate
the earliest
you hear a
tone
Ex: listen to
headphones
and indicate
when you hear
a change in
volume of
sound
Sensation- Thresholds
• Signal Detection Theory
Percentage
– predicts how and when we
of correct
detect the presence of a faint
detections
stimulus (signal) amid
background stimulation (noise)
– assumes that there is no single
When stimuli are
absolute threshold
detectable less
– detection depends partly on than 50% of the
person’s
time (below one’s
absolute threshold)
-experience
-motivation
they are
-expectations -level of fatigue “subliminal”.
100
75
50
Subliminal
stimuli
25
0
Low
Absolute
threshold
Intensity of stimulus
Medium
Sensation- Thresholds
• Weber’s Law- to perceive a difference between
two stimuli, they must differ by a constant
proportion
– light intensity- 8%
– weight- 2%
– tone frequency- 0.3%
• Sensory Adaptation: diminished sensitivity with
constant stimulation
- receptors higher up in sensory system get tired
and fire less frequently
Apply it!
Come up
with 3
examples
Perception…
Perception is important because:
It is the key mediator between stimulus and
response
It is the source of most knowledge that humans
acquire
Input (stimulus)
Output (response)
The Study of Perception is
Highly Interdisciplinary
•
•
•
•
•
•
•
•
•
•
Art
Music
Philosophy
Mathematics
Engineering
Biology
Medicine
Psychology
Human Factors
Law
Perception is…
• Largely an unconscious process, and thus it
complexity tends to be underestimated
• Transparent to the perceiver – we notice it
only when it misfires. Examples: the blind
spot; neglect.
Psychology vs. Biology
•
•
•
•
The Mind Body Problem
Neurons and Grandmother Cells
Psychophysics
Hermann Grid
Hermann Grid
The Scintillation Grid: Bernd Lingelbach
Ways to Study Color Vision
• Psychophysics: Do these two colors match?
• Neuroanatomy: How many cones in the eye?
• Neurophysiology: What stimulus activates this cell in the
visual cortex?
• Clinical observation: What colors disappear in color
blindness?
• Computational engineering: How can we build a system
that sees colors the way we do?
• Visual art: Will these colors clash or please?
• Marketing: Do these colors capture attention?
Vision
Did you know major league batters can hit a 90 mile per hour fastball 4/10 of a
second after it leaves the pitcher’s hand?
• Transduction: conversion of one form of energy to another
• Wavelength: the distance from the peak of one wave to the peak of
the next
• Hue: dimension of color determined by wavelength of light
• Intensity: amount of energy in a wave determined by
amplitude
– brightness
– loudness
Vision:
Spectrum of
Electromagnetic
Energy
Vision: Physical Properties of Waves
Short wavelength=high frequency
(bluish colors, high-pitched sounds)
Great amplitude
(bright colors, loud sounds)
Long wavelength=low frequency
(reddish colors, low-pitched sounds)
Small amplitude
(dull colors, soft sounds)
Vision: Parts of the Eye
•
•
•
•
Cornea: transparent covering on the front of the eye
Fovea: central point of focus on the back of the eye
Pupil: adjustable opening in the center of the eye
Iris: a ring of muscle the forms the colored portion of the eye around the
pupil and controls the size of the pupil opening
• Lens: transparent structure behind pupil that changes shape to focus images
on the retina
Accommodation: change in shape of lens focus near objects
• Retina
– Layers of neurons on inner surface of eye
– light sensitive
– contains rods and cones
– beginning of visual information processing
Blind Spot: area of retina where optic nerve leaves back of eye
Vision: Parts of the Eye
Retina’s Reaction to Light Receptors
Rods
• Located in periphery of retina
• detect black, white and gray
• twilight or low light
Cones
– near center of retina (fovea)
– fine detail and color vision
– daylight or well-lit conditions
Receptors in the Human Eye
Cones
Rods
Number
6 million
120 million
Location in
retina
Center
Periphery
Sensitivity in
dim light
Low
High
Color sensitive?
Yes
No
Pathways from the Eyes to the Visual Cortex
A true “optical” illusion
R. C. James Photograph
Visual Perception:
Gestalt
• Gestalt Principles (gestalt = an
organized whole. We tend to
integrate pieces of info. into
meaningful wholes)
– Proximity
– Simplicity (law of good form)
– Connectedness
– Closure
– Continuity
– Similarity
– Phi Phenom
Pictorial depth cues
Drawing and Visual Cues
• https://www.youtube.com/watch?v=VKqKzgKUDEI
Necker Cube
Subjective Necker Cube
Audition (Hearing)
– Audition
• the sense of hearing
– Frequency
• the number of complete wavelengths that pass a point in a given time
– Pitch
• a tone’s highness or lowness
• depends on frequency
The Stimulus
Vibrations of sound waves
 Amplitude: loudness
 Wavelength: pitch
 Purity: timbre
The Intensity of Some Common Sounds
Audition: The Ear
• Outer Ear
– Auditory Canal
– Eardrum
• Middle Ear
– hammer
– anvil
– stirrup
• Inner Ear
–
–
–
–
oval window
cochlea
basilar membrane
hair cells
Touch
• Skin Sensations
– pressure
• only skin sensation
with identifiable
receptors
– warmth
– cold
– pain
Pain
• Gate-Control Theory
– Theory that the spinal cord contains a neurological
“gate” that blocks pain signals or allows them to
pass on to the brain
– “gate” opened by the activity of pain signals
traveling up small nerve fibers
– “gate” closed by activity in larger fibers or by
information coming from the brain
• Taste Sensations
Taste
– sweet
– sour
– salty
– bitter
• Sensory Interaction
– the principle that one sense
may influence another
– as when the smell of food
influences its taste
The Stimuli: chemical substances
that are soluble
The Anatomy: taste buds act as
the receptors for taste (about
every two weeks)
Perception of taste & flavor
 Numerous factors can impact
the flavor of food (Ex:
temperature of the food, texture,
prior condition of the mouth, health
state of the organism, smell)
The
Tongue
Smell (Olfaction)
The Stimuli: chemical substances
that are soluble
The Anatomy: receptors are
olfactory cilia which lie on the
roof of the nasal passage and
sinus
Sense DOES NOT get filtered by
thalamus
Taste and smell interact to
produce flavor
Touch
• Numerous types of
receptors lie in varying
depths in the skin
• Four Basic Skin Senses
– Hot
– Cold
– Pressure
– Pain
Body Position and Movement
• Kinesthesis
– the system for sensing the position and
movement of individual body parts
• Vestibular Sense
– the sense of body movement and
body’s position relative to gravity
– including the sense of balance
– Semicircular canals in ears
States of Consciousness
Chapter 5
-Understanding Consciousness
- Sleep and Dreams
Circadian Rhythms, Stages of Sleep,
Why Do We Sleep & Dream?
Sleep Disorders, Self-help for Sleep Problems
- Psychoactive Drugs
- Healthier Ways to Alter Consciousness
Consciousness
• Definition: An individual’s perceptions, thoughts, feelings, and
memories that are active at a given moment.
Or “an organism’s awareness of its own self and surroundings”
• Awareness of:
• Internal sensations
• External events
• Self as a unique being
• Thoughts and experiences
• Characteristics: Personal and subjective, occurring on a continuum,
and changing all the time.
Function of Consciousness
• Monitoring
• Monitoring the environment for what is and what isn’t
important
• Selective Attention: the ability to choose what to allow
into consciousness
• Cocktail Party Phenomenon
• Controlling
• Used to plan and change our actions
Conscious/Unconscious Continuum- Freud’s Theory
Subconscious
• ignore, select and reject incoming stimuli
• Ex: clock chiming the hour
Preconscious
• Available memories
Unconscious
• Freudian slips, repressed memories, dreams
Divided Consciousness
• Ability to do two things at once
• Controlled vs. Automatic processes
Rhythms in humans
• Yearly, 28 day, 90 minute
• 24 hour (Circadian) Rhythms: alertness, body temp, hormones
• What happens if no external cues?
• Jet lag
West to East Phase advance
•
East to West Phase delay
• Sleep Deprivation
Theories on Sleep
There is no physiological reason found for sleep
Adaptive: Species need a certain time awake to survive. Sleep protects
by keeping out of trouble.
Conserving Energy: Less calories burned.
Restorative: Restore body and nervous system
The Cycles of Sleep
• Repeats about every 90 minutes
• REM sleep increases at the night moves on
• About 25% of sleep is REM
Sleep as a change in consciousness
Sleep Stages
• Stage 1
• Stage 2
• Stage 3
• Stage 4
• REM
Collectively called NREM stages
EEG Cycles
Sleep Stages and Characteristics
Stage 1
Stage 3
Stage 2
• A purely transitional stage
Theta Waves,
• About 20
• marked by 20-50% delta waves
irregular,
minutes long
breathing slows,
• Characterized
light sleep, easily
Stage 4
by
sleep
awakened, lasts
• About 30 minutes long
spindles
and
K
about two
• Hard to awaken
Complexes
minutes, may
• Delta waves > than 50% of the time
have sensory
• easily awakened
• Walking or talking in sleep, wetting the
experience
but clearly
bed, and night terrors can occur during
without stimulus
this stage
asleep
• Still attend to external stimuli
Sleep Stages REM
REM
• Occurs the first time about an hour into the sleep
cycle
• Brain waves rapid
• Breathing and heart rate rapid
• Arousal of genitals
• Rapid eye movement
• Essentially paralyzed during this stage
• Cannot easily be awakened
Specific Sleep Disorders
Sleep Apnea
Nightmares
Narcolepsy
Sleep
paralysis
Insomnia
REM without Atonia
Restless leg
Sleep walking, talking
Night Terrors (NREM) children,
sudden terror
Function of Sleep
Deprivation studies for REM sleep result
in:
• hand tremors
• crankiness
• inability to pay attention, concentrate
• reports of being sleepy
• reported hallucinations
• REM rebound which occurs once normal
sleep cycle is allowed to return
Dreaming
• Dreams can occur at any stage
• Content and clarity of dream depends on which
stage it occurs in
• Dreams in sleep stage 1-4 generally lack detail
and are more associated with reports of
emotion (ex: “It felt like I was being chased”)
• REM dreams are detailed and are associated
with story lines (ex: I was walking down a
dimly lit street, wearing high heels…”)
The Function of Dreaming
• Function
• Wish Fulfillment (Freud):
Manifest (actual) and latent contents (symbolic)
• Information Processing (Cartwright):
The need to continue processing the day’s activities.
Solves problems
• Activation Synthesis Hypothesis (Hobson & McCarley):
Triggered by neural activity from the brainstem
Dreaming: pic
Most Common Dreams
Falling
Being attacked
Trying repeatedly to do something
School, teachers, exams
Sex
Arriving too late
Frozen with fright
Death of a loved one
Nudity/Inappropriate dress
Killing or seeing themselves dead
Fire/ Snakes
Hypnosis
Heightened state of suggestibility
Posthypnotic suggestions and amnesia
Theories: Disassociation, role, state
Best subjects: fantasize, imaginations, good concentration, think favorably
Facts and fallacies
Fun Example
https://www.youtube.com/watch?v=QqdywcGsOp4
Alternate form of Consciousness
Psychoactive Drugs
Factors influencing drugs effects
• Tolerance
• Weight
• Physiology
• Amount and strength
• Mood
• Personality
• Age
• Gender
Drugs and Consciousness
Stages in drug use
• Tolerance: The need to use more and more of a drug to continue to get
the same effects
• Dependence
• Physiological: Showing a withdrawal syndrome once
removed from the drug regimen
• Psychological: An emotional need for the drug
• Co-dependence
• Withdrawal: A distinct set of physiological symptoms associated with the
removal of the drug from the system
Use of Drugs - Percentage
“This picture demonstrates the debilitating
effects of drug use. You can clearly see the
physical breakdown that occurs with the abuse
of drugs. What you don't see but can imagine
is the loss of jobs, relationships and family.”
http://www.houstoncriminallawjournal.com/art
icles/drug-possession/
Classifications of Drugs
• Stimulants: Drugs that stimulate CNS activity
• Examples - amphetamines, caffeine,
nicotine
• Depressants: Drugs which decrease CNS
activity
• Examples - Alcohol, Barbiturates, Minor
tranquilizers
• Hallucinogens: Drugs that change perception
and self-awareness
• Examples - LSD, PCP, marijuana
Depressants
• Barbiturates:
• Anti-Anxiety: calms nervous
system
• Alcohol: Reduces
inhibitions. Males more
likely to coerce sex, tip and
spend big.
Stimulants
• Amphetamines: Speeds
up nervous system.
Often an initial euphoria
or gain in energy
followed by a crash
Examples: Meth,
cocaine, nicotine, Ritalin,
“speed”
Opiates
Narcotics
Pain killers:
Heroin, oxycotin,
codeine,
morpheme
Kills pain,
restricts pupils,
sedates
Hallucinogens
• Behavioral Changes
observed?
• Mimic psychosis
• Examples – LSD,
Peyote
Marijuana
Does not fit neatly into any category,
although usually classified as hallucinogen,
it can act like a depressant and a
stimulant, and a pain killer.
Active drug THC
Much stronger than in previous
generations.