Download Perceiving forms, patterns and objects

Overheads, Perception and Consciousness
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Unit 3: Perception and Consciousness
Sensation: the stimulation of sense organs.
Perception: the selection, organization, and interpretation of sensory input.
Signal detection theory: the detection of stimuli involves decision
processes as well as sensory processes, influenced by other factors besides
stimulus intensity.
Hits: detecting signals when they are present
Misses: failing to detect signals when they are there
False Alarms: detecting signals when they are not there
Correct Rejections: not detecting signals when they are in fact absent
Depends on expectations, the consequences for missing a signal or for
reporting a false alarm, and on how much “noise” there is in the system.
Noise: the irrelevant stimuli in the environment and the neural activity they
elicit.
Detectability: measured in terms of probability and depends on decisionmaking processes as well as sensory processes
Subliminal perception: the registration of sensory input without conscious
awareness.
1957: James Vicary’s hidden messages in films.
1992: Krosnick’s research using slides and subliminal photos
concluded that perception without awareness CAN take place.
Sensory Adaptation: a gradual decline in sensitivity to prolonged
stimulation

an automatic, built-in process that keeps people tuned into the
changes rather than the constants in their sensory inputs

changes may signal threats to safety, or provide new
information about the world
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Perceiving forms, patterns and objects

No one-to-one correspondence exists between sensory input
and what you perceive.

Our experiences of the world are ultimately subjective.

Expectations can be altered by information you receive,
which creates a perceptual set: a readiness to perceive a
stimulus in a particular way
Feature Analysis: detecting specific elements in visual inputs and
assembling them into a more complex form.

bottom-up processing: begin with components of a form and
build them into perceptions of shapes, objects

top-down processing: a progression from the whole to the
elements.
Gestalt psychology: a school of thought from Germany in the 1st half of the
20th century

when it comes to perception, the whole can be greater than
the sum of the parts.
Phi phenomenon: the illusion of movement created by presenting visual
stimuli in rapid succession
Figure and Ground: we divide visual displays into figure and ground. The
figure is the thing being looked at; the ground is the background against
which it stands.
Proximity: things that are near to each other seem to belong together.
Similarity: we group together stimuli that are similar.
Continuity: we connect points that result in straight or gently curved lines
that create “smooth” paths
Simplicity (pragnanz): we group elements that combine to form a “good
figure” (i.e. a simple figure)
Closure: we group elements to create a sense of closure, or completeness
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2 kinds of stimuli
Distal stimuli: lie in the distance, i.e. the world outside the body
Proximal stimuli: the energies that impinge directly on sense receptors
How do we “know” about distal stimuli when the proximal stimuli can be so
distorted?
 we test hypotheses about what’s out there in the real world
 perceptual hypothesis: an inference about which distal stimuli could be
responsible for the proximal stimuli sensed
 ambiguous stimuli: perceptual set influences what people see
Depth and Distance
Binocular cues:
- each eye gets a slightly different view of the world. These give us
cues as to how far away things are, based on how much the 2
views from the 2 eyes are different.
- Retinal disparity: objects within 25 feet project images to slightly
different locations on the right and left retinas; the closer an object
gets, the greater the disparity.
- Convergence: sensing the eyes converging toward each other as
they focus on closer objects
Monocular cues:
- cues based on the image in either eye alone
- as objects come closer, we sense the eye’s lens changes in
curvature to focus it
- motion parallax: images of objects at different distances move
across the retina at different rates
Pictorial depth cues:
1. linear perspective: lines converge in the distance
2. texture gradients: texture is coarser close up than far away
3. interposition: if an object comes between you and another object you
know it’s closer
4. relative size: closer objects appear larger
5. height in plane: distant objects appear higher in a picture
6. light and shadow can help us judge distance
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 use of these cues differs from culture to culture
 people from tribes where there is little exposure to pictures
and photos misinterpret depth cues in pictures
Perceptual constancies in vision: we see things as having a stable size,
shape, brightness, hue, and location in space.
 Ponzo illusion
 Upside-down T
 The Moon Illusion
Consciousness
William James: a “stream of consciousness” that constantly shifts and
changes.
Freud: people’s feelings and behavior are influenced by unconscious needs,
wishes, conflicts that lie below the surface of conscious awareness.
circadian rhythm: the 24-hour biological cycle that regulates sleep, daily
variations in blood pressure, urine production, hormonal secretions, body
temperature, etc.
- when exposed to light, some receptors in the retina send messages
to the suprachiasmic nucleus (SCN) (found in the hypothalamus)
- SCN sends signals to the pineal gland, which alters its manufacture
of melatonin (light  less melatonin; dark  more melatonin)
 jet lag
 going to bed late
 night shifts, rotating shifts
Melatonin:
 melatonin may reduce the effects of jet lag
 may also be effective as a mild sedative to treat insomnia.
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What is Sleep?
Sleep research happens in sleep labs
 Electroencephalogram (EEG)  brain activity
 Electromyograph (EMG)  muscle movements and tension
 Electrooculograoh (EOG)  eye movements
 heart rate, breathing, pulse, temperature
The stages of sleep
Stages 1-4: non-REM sleep
 stage 1: a brief transitional stage of light sleep, lasting 1-7
minutes
- breathing and heart rate slow
- muscle tension and temperature decline
- the alpha waves of drowsiness give way to theta
waves
- hypnic jerks occur in this stage
 stage 2 lasts 10-25 minutes, and is characterized by sleep
spindles and mixed EEG activity. Waves gradually get
higher and slower and the body moves toward deep sleep.
 Stages 3 & 4 are slow wave sleep, or deep sleep: high
amplitude low frequency delta waves are prominent. It takes
about 30 minutes to get to deep sleep, and once there, we
stay in it for 30 minutes.
 Then the cycle reverses itself and the sleeper gradually
moves back upward through the lighter stages.
 Once the sleeper reaches what would be stage 1 again they
go into a 5th stage, REM sleep.
- A deep sleep stage
- irregular breathing, pulse, muscle paralysis
- beta waves that look like the awake brain
- associated with reports of vivid dreaming
 Sleep is regulated by subcortical structures deep within the brain
 Reticular formation contains the ascending reticular
activating system (ARAS)
 Pons  REM sleep
 medulla, thalamus, hypothalamus and limbic system
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 Neurotransmitters implicated in sleep and waking:
 ACTH and 5-HT
 Also NE, DA, and GABA
Sleep Deprivation
 Complete deprivation: modest negative effects on mood,
cognitive tasks, perceptual-motor tasks
 Partial deprivation (a.k.a. sleep restriction): effects depend
on the amount of sleep lost and the nature of the task. Worst
effects for long-lasting, difficult, or monotonous tasks, or
when people restrict sleep to 5 hours or less for several
nights.
Research with college students:
- sleep deprived students score significantly lower on cognitive tasks
- however, they rate their effort, concentration, and performance
higher than they rate the performance of nondeprived students!
Other research:
- partial sleep deprivation impairs attention, reaction time, motor
coordination, decision making
- contributes to transportation accidents and workplace mishaps
- 23% of people in 1 survey reported that they had fallen asleep
while driving
- especially susceptible groups: truck drivers, young drivers, people
on rotating shifts
- night-time workers frequently fall asleep on the job – e.g. 59% of
train engineers admit to having dozed off while on duty at night
- accidents like 3 Mile Island, Chernobyl, the Exxon Valdez, have
been linked to sleep deprivation among other things
Selective deprivation: studies have looked at what happens when you give
people all the sleep they want but you restrict certain stages of sleep
 REM deprivation:
- little impact on daytime functioning, task performance
- start entering REM more frequently throughout the night
- rebound effect - enter REM earlier and stay in it longer
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 slow-wave sleep deprivation:
- rebound effects
Sleep Disorders
Insomnia: chronic problems in getting adequate sleep
(1) trouble getting to sleep initially
(2) trouble staying asleep
(3) persistent early morning awakening
 fatigue, impaired functioning, more health problems
 about 15% of adults report severe or frequent insomnia;
another 15% complain about mild or infrequent insomnia
 Prevalence increases as we get older
 Pseudoinsomnia (a.k.a. sleep state misperception): about
5% of people who complain about insomnia.
Causes: anxiety, tension, emotional problems, stress, health problems, use
of stimulants
Treatment:
sedative drugs help people fall asleep more quickly, reduce the number of
nighttime awakenings, and increase total amount of sleep.
- poor long-range solution  danger of overdose, development of
dependency, get less effective with prolonged use
- interfere with the amount of time spent in REM and slow-wave
sleep!!!
- can cause even worse insomnia than before when stopped
Other treatments: cognitive behavioral treatments, sleep-hygiene information
Narcolepsy: sudden and irresistible bouts of sleep during normal waking
periods.
- goes directly from waking to REM sleep for about 10-20 minutes.
- Genetic predisposition in some sufferers
- Treated with stimulant drugs with modest success
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Sleep apnea: frequent, reflexive gasping for air that awakens the person and
disrupts sleep
- Some wake up hundreds of times a night – micorawakenings
- stops breathing for 15 to 60 seconds
- 5% of men aged 40 to 60
- can disrupt sleep and lead to insomnia
- can also lead to heart and lung damage
- treatments: surgery, drug therapy, forced oxygen intake masks
Nightmares: anxiety-arousing dreams that lead to awakening, usually from
REM sleep
- stress is associated with increased frequency of nightmares
- 10% of adults have occasional nightmares
- common in children - usually they outgrow them
Night terrors (a.k.a. sleep terrors): abrupt awakenings from NREM sleep
accompanied by intense autonomic arousal and feelings of panic
- usually during stage 4 sleep
- person cries out then bolts upright and stares into space.
- do not recall a dream; some recall a simple frightening image
- panic fades quickly & people go back to sleep
- common in children age 3 to 8
- not indicative of emotional problems
- typically children grow out of them
Somnambulism (a.k.a. sleepwalking): when a person arises and wanders
about while remaining asleep
- first 2 hours of sleep, in slow-wave sleep
- may wake up while walking, may go back to bed without waking
up
- unknown etiology
- possible genetic predisposition
- not related to underlying emotional or psychological problems
- peaks at age 11 or 12 – usually outgrow it
- occasionally seen in adults
- prone to accidents while sleepwalking
- yes it is safe to wake up a sleepwalker
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Dreams: mental experiences during REM sleep that have a storylike quality,
include vivid visual imagery, are often bizarre, and are regarded as
perceptually real by the dreamer.
However!
 dreams are not as bizarre as is widely assumed
 dreams also do occur outside of REM, though they are less vivid and
storylike
 people realize they are dreaming more often than was previously thought
Dream Content
- not as exciting as you think
- mundane things - in familiar settings, with familiar people
- common themes: sex, aggression, misfortune
- men: dream more of strangers, automobiles, weapons, acting
aggressively, sex dreams about liaisons with strangers
- dream more of children, clothing, jewelry, being the target of
aggression, sex dreams about their partner
Dreams and Waking Life
- dream content is affected by what’s going on in our lives
- Freud: waking life spills into dreams  the “day residue”
- can also be affected by stimuli experienced while one is dreaming
Dreams and Culture
- Western view: there’s the real world and then there's the dream
world, which is imaginary.
- many non-Western cultures see dreams as important sources of
information about oneself, the future, the spiritual world
- some dream themes are universal: falling, being pursued, having
sex
- some themes are culture specific because of the different realities
in the waking world
Freud: the purpose of dreams is wish fulfillment.
- the true meaning of the dream is disguised, and needs to be
interpreted
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Rosalind Cartwright: dreams provide an opportunity to work through
everyday problems
Hobson & McCarley : dreams are the by-product of bursts of electrical
activity emanating from subcortical areas in the brain
- they are side-effects of the neural activation that produces “wide
awake” brain waves during REM sleep
- neurons firing in the lower brain centers send random signals to the
cortex, which synthesizes a dream to make sense out of these
signals
Hypnosis
 a procedure which, it is claimed, produces a heightened state of
suggestibility
10% of people do not respond at all.
10% of people respond exceptionally well.
 Franz Anton Mesmer
 James Braid
 suggestibility is related to absorption and imaginativeness
 the big predictor of who will be hypnotizable and who won’t is the
attitudes and expectations the person has about hypnosis and what to means
to be hypnotized
Hypnotic phenomena:
1. Anesthesia. Claims that hypnosis can be used for treatments that
normally cause considerable pain.
2. Sensory distortions and hallucinations. Claims that you can get people
to see things or hear things that are not there.
3. Disinhibition. Claims that a person’s inhibitions may be reduced and
they can act in ways they would not otherwise.
4. Posthypnotic suggestions and amnesia. If pressed, many admit that
they actually do remember the information they are supposed to be
amnesic for.
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The altered state versus role-playing controversy
Altered state.
 Hilgard
 Who’s going to pretend to be anesthetized just to please
their hypnotist?
 Hypnosis creates a dissociation in consciousness - a
splitting off of mental processes into 2 separate
simultaneous streams of consciousness, one of which is in
communication with the hypnotist while the other is a
“hidden observer”
Role-playing.
 Barber and Spanos
 people act out the role of a hypnotic subject and behave as
they think hypnotized people are supposed to behave
 Many of the “amazing” effects of hypnosis have been
duplicated by nonhypnotized subjects or have been shown
to be exaggerated
 no evidence that hypnosis enhances memory
 Regressions to earlier in life or to past lives have been
demonstrated to be fantasy experiences, not real

Drugs
Psychoactive drugs: chemical substances that modify mental, emotional, or
behavioral functioning.
Narcotics, or opiates:
- drugs derived from opium, capable of relieving pain
- heroin, morphine, codeine, Demerol, methadone
- sense of euphoria or well-being
- side effects: lethargy, nausea, impaired motor functioning
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Sedatives:
- sleep-inducing drugs, decrease CNS activity & behavioral activity
- includes the barbiturates, compounds derived from barbituric acid
- can yield a “high” much like drinking alcohol - relaxation,
pleasant intoxication, loosened inhibitions
- side effects: drowsiness, unpredictable mood swings, impaired
motor coordination, impaired mental functioning
Stimulants:
- increase CNS activity and behavioral activity
- includes caffeine, nicotine, cocaine, amphetamines
- buoyant, energetic “I can conquer the world” feeling, plus
increased alertness
- freebasing  a chemical treatment used to extract nearly pure
cocaine from ordinary street cocaine (crack)
- amphetamines are increasingly sold as crystalline powder (crank)
that can be snorted or injected
- smokable form of methamphetamine (ice)
- Side effects: restlessness, anxiety, paranoia, insomnia
Hallucinogens
- powerful effects on mental and emotional functioning, distortions
in sensory and perceptual experience
- LSD, mescaline, psilocybin
- euphoria, increased sensory awareness, distorted sense of time
- profound, mystical, dreamlike feelings
- anxiety and paranoia  “a bad trip”
Cannabis
- the hemp plant that yields marijuana, hashish, and THC
- smoked: immediate impact that can last several hours
- mild, relaxed euphoria and enhanced sensory awareness
- side effects: anxiety, slow mental functioning, impaired memory
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Alcohol
- concentration varies from 4% (beer) to 40% or more
- relaxed euphoria, boost to self-esteem, reduction of inhibitions
- side effects: impairment of mental and motor functioning, mood
swings, quarrelsomeness
- many social problems result from abuse of alcohol
- on campus: 34% of students reported that they had been insulted or
humiliated by a drunken student; 20% reported serious arguments;
13% reported being assaulted or pushed.
- contributes to 90% of student rapes and 95% of violent crimes on
campus
- 41% of binge drinkers on campus reported they had unplanned sex
due to overdrinking
- 22% reported their drinking led to unprotected sex
- associated with poor academic performance
Drug Effects
tolerance: a progressive decrease in a person’s responsiveness to a drug
 leads people to consume larger and larger doses to attain the
same effects
 tolerance to alcohol builds slowly; tolerance to heron
happens very quickly
amphetamines & cocaine: effects on NE and DA sites
- increase release of DA and NE by the presynaptic neurons
- interfere with reuptake of DA and NE from synaptic clefts
sedatives: exert effects at GABA sites
- leads to increased activity in the GABA system
- alcohol acts on the GABA system, and DA, 5-HT, and others
- alcohol has a synergistic effect with other sedatives: the combined
effect is greater than the sum of the individual effects
- so mixing alcohol with sedatives can lead to fatal overdoses
opiates: bind to specific opiate receptors in our brains
- leads to an impact on DA sites, increasing DA activity
LSD: impacts on serotonin sites
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THC: - receptors in the brain that fit this chemical
- our brain makes its own version, called anandamide
- anandamide can impair recent memory and stimulate overeating in
lab animals
 virtually all abused drugs eventually increase activity in the mesolimbic
dopamine pathway (the “reward pathway”)
Dependence
Physical dependence: person must take the drug to avoid withdrawal
- heroin, barbiturates, alcohol: fever, chills, tremors, convulsions,
vomiting, cramps, diarrhea, aches and pains
- stimulants: fatigue, apathy, irritability, depression, disorientation
Psychological dependence: person must take the drug to satisfy mental and
emotional cravings
Drugs and Health
- rats given unlimited access to heroin or cocaine
 rats on cocaine lost 29% of body weight
 by end of 30 days, 90% had died
 36% of rats on heroin died in their study
 many experienced severe unpleasant seizures but did not
stop using the drugs
Overdose
Depressants: drugs that are CNS depressants carry the greatest risk of
overdose. Combining sedatives, narcotics, and alcohol can result in a lethal
combination.
- respiratory system grinds to a halt
- leads to coma, brain damage, death, pretty quickly!
Stimulants: death typically due to heart attack, stroke, or cortical seizure.
- less common than deaths due to depressant overdoses
- newer forms of freebased cocaine (crack) and speed (crank, ice)
have led to increases in the # of overdoses in the past several years.
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Direct Effects:
 drugs can cause tissue damage directly
- cocaine can damage nasal membranes, alter
cardiovascular functioning, causing increased risk of
heart attack and stroke
- crack smoking can lead to respiratory problems
 alcohol consumption leads to greater risk for a whole host of
problems, including liver damage, ulcers, hypertension,
stroke, heart disease, neurological problems, and some kinds
of cancer
Indirect effects:
 stimulantsusers tend not to eat properly or sleep enough
 sedatives  risk of accidental injuries due to impaired
motor coordination
 alcohol  contributes to about 40% of automobile fatalities
 i.v. drug users  at risk for contracting infectious diseases
via unsterilized needles