Transcript SR6eChapter6

CHAPTER 6
SENSATION, PERCEPTION, AND ATTENTION
Learning Objective
• What are the views of constructivists and
nativists on the nature-nurture issue as it
relates to sensation and perception?
Nature and Nurture
• Constructivists – on the side of nurture
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– Argue that perceptions are constructed
through learning
Nativists – on the side of nature
– Argue that innate capabilities and
maturational programs drive perceptual
development and that perception does not
require interpretation
Learning Objectives
• How are perceptual abilities of infants
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assessed?
What are infants’ visual capabilities?
What sorts of things do infants prefer to look
at?
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The Infant – Assessing Sensory and
Perceptual Abilities
The main methods used to study infant
perception
– Habituation
– Preferential looking
– Evoked potentials
– Operant conditioning
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The Infant – Assessing Sensory and
Perceptual Abilities
Habituation
– The process of learning to be bored with a
stimulus
• After repeated presentation with the same
visual stimulus, the infant becomes bored
and looks away
• If a different stimulus is presented and the
infant regains interest, researchers
conclude that the infant has discriminated
between the two stimuli
– Habituation can be used to test for
discrimination of stimuli by all the senses
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The Infant – Assessing Sensory and
Perceptual Abilities
Preferential looking
– Researchers present an infant with two
stimuli at the same time and measure the
length of time the infant spends looking at
each
• A preference for one over the other
indicates that the infant discriminates
between the two stimuli
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The Infant – Assessing Sensory and
Perceptual Abilities
Evoked potentials
– Researchers can assess how an infant’s
brain responds to stimulation by measuring
its electrical conductivity
Operant conditioning
– Infants can learn to respond to a stimulus
(to suck faster or slower or to turn the
head) if they are reinforced for the
response
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The Infant – Vision
Basic visual capacities are present at birth
– Can detect changes in brightness and can track
a slow-moving object or picture
Visual acuity – ability to perceive detail
– Optimal at about 8 inches from the face or if
objects are boldly patterned with sharp light-dark
contrasts
Visual accommodation – ability to focus on objects
at different distances
– Takes 6 months to 1 year before can see as well
as an adult
Color vision present at birth
– Color vision mature at 2 to 3 months
• Caption: Eye chart
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Caption:
What the
young eye
sees
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The Infant – Vision
Infants’ visual preferences
– Attracted to patterns that have light-dark
transitions, or contour
• Sharp boundaries between light and dark
areas, such as offered by black and white
objects
– Attracted to displays that are dynamic – contain
movement – rather than static
• Can track a slow-moving object
– Attracted to moderately complex patterns
• Prefer clear patterns (checkerboard) to blank
or complex stimuli
– Prefer “top-heavy” patterns such as the
human face
• Caption: Visual
scanning in early
infancy
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The Infant – Vision
Explanation of Martin Banks and colleagues for
infants’ visual preferences: “Young infants prefer
to look at whatever they can see well”
– Seem to actively seek the visual input they
can see well and that will stimulate the
development of the visual centers of their
brains
Around 2 or 3 months, a breakthrough begins to
occur in the perception of forms
– 1-month-olds focus on the outer contours of
forms such as faces (a person’s chin, hairline,
top of the head)
– Around 2 months, infants begin to explore the
interiors of figures thoroughly (facial features)
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The Infant – Vision
Depth perception
– Newborns appear to have size constancy
• Recognition that an object is the same size
despite changes in its distance from the eyes
– Classic study to examine depth perception in
infants using the visual cliff: Gibson & Walk (1960)
• Most infants older than 6 ½ months crossed the
“shallow” pattern but would not cross the “deep”
or “cliff” pattern
• Infants can perceive the cliff by 2 months
• Most infants of crawling age (typically 7 months
or older) clearly perceive depth and have
learned to fear drop-offs
Caption: An infant on the edge of a visual
cliff, being lured to cross the “deep” side
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The Infant – Vision
Researchers have shown that 3-month-old infants
can detect deviation from well-formed and
symmetrical patterns
4-month-olds use common motion as an important
cue in determining what is or is not part of the same
object
– Use “good form” to perceive an object’s unity or
wholeness
Around 6 months of age, infants can determine the
boundaries or edges of stationary objects
Conclusion is that infants have intuitive theories –
organized systems of knowledge – that allow them
to make sense of the world
Learning Objectives
• What are the auditory capabilities of
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infants?
What do researchers know about
infants’ abilities to perceive speech?
What are the taste and smell
capabilities of infants?
To what extent are infants sensitive to
touch, temperature, and pain?
The Infant – Hearing
• Basic capacities are present at birth
– Can hear better than they can see
– Can localize sounds
– Can be startled by loud noises
– Can turn toward soft sounds
– Prefer relatively complex auditory stimuli
– Can discriminate among sounds that differ
in loudness, duration, direction, and
frequency/pitch
The Infant – Hearing
• Infants respond to human speech and prefer
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speech over non-speech sounds
Can discriminate basic speech sounds –
phonemes
– The pioneering research of Eimas (1975,
1985) demonstrated that infants could
distinguish similar consonants (ba and pa)
and vowels (a and i) and between standard
and rarely heard sounds
The Infant – Hearing
• Infants become increasingly sensitive to
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sound differences that are significant in their
own language and become increasingly
insensitive to sounds not made in their native
language
– Early auditory experiences shape the
formation of synapses in the auditory areas
of the brains and create optimal sensitivity
to the sounds in the native language
Newborns attend to female voices and can
recognize their mothers’ voices, even in utero
The Infant – Taste and Smell
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Newborns can distinguish sweet, bitter, and sour
tastes
– Prefer sweet
– Facial expressions reflect taste sensations
Olfaction – sensory receptors for smell – work
well at birth
– Will turn head away from unpleasant smells
– All babies prefer the smell of human milk over
formula, even if previously consumed formula
– At 1 to 2 weeks, breast-fed babies can
recognize the smell of their mother’s breasts
or underarms
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The Infant – Touch, Temperature, and Pain
The senses of touch and motion develop before birth
– Sensitivity to tactile stimulation develops in a
cephalocaudal direction
– Touch soothes a fussy baby
– Systematic massage helps premature infants to
gain weight, be more relaxed, and develop more
regular sleep patterns
Newborns are sensitive to warm and cold and to
painful stimuli
– Infants respond to pain and learn from the
experience
– The American Academy of Pediatricians
recommend that newborn males be given local
anesthesia at circumcision
Learning Objectives
• To what extent can infants integrate their
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sensory experiences?
What is an example of cross-modal
perception?
What role do early experiences play in
development of perceptions?
What factors contribute to normal visual
perception?
The Infant – Integrating Sensory Information
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At birth, sensory functions are integrated
– Newborns will look in the direction of the sound
they hear and expect to feel objects they can see
– Integration of the senses helps babies perceive
and respond appropriately to the objects and
people they encounter
Cross-modal perception is to recognize through one
sense an object that is familiar through another sense
– A fragile ability that researchers are challenged to
demonstrate in infants
• Continues to improve through childhood and
adolescence
The Infant – Influences on Early Perceptual
Development
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Early perceptual development is evidence for nurture
– Basic perceptual capacities appear to be innate or
to develop rapidly in all normal infants
– Research of Hubel and Torsten (1970)
demonstrated the critical period for the
development of vision in kittens: blindness resulted
from deprivation of normal visual experiences for 8
weeks
– Among humans, early experiences affect the
development of vision during multiple sensitive
periods
• “. . . a window of time during which an individual
is more affected by experience, and thus has a
higher level of plasticity than at other times
throughout life . . . ”
The Infant – Influences on Early Perceptual
Development
• Sensory experience is vital in determining the
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organization of the developing brain
– The visual system requires stimulation early
in life to develop normally
• Early visual deficits (i.e., congenital
cataracts) can affect later visual
perception
Exposure to auditory stimulation early in life
affects the architecture of the developing brain
and influences auditory perception skills
The Infant – The Infant’s Active Role
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Gibson (1988) suggested that infants engage in three
phases of exploratory behavior
– From birth to 4 months, infants explore their
immediate surroundings by looking and listening
and especially by mouthing objects and watching
them move
– From 5 to 7 months, once infants can grasp, they
explore objects with their hands as well as with
their eyes
– By 8 or 9 months, infants use crawling to extend
their explorations into the larger environment and
carefully examine an object by fingering it, poking it,
and watching it
The Infant – The Infant’s Active Role
• The combination of perception and action
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in exploratory behavior enables children
to create sensory environments that meet
their needs and contribute to their own
development
They are able to attend selectively to the
world around them and choose the forms
and levels of stimulation that suit them
best
The Infant – Cultural Variations
• People from different cultures differ little
in basic sensory capacities, such as the
ability to discriminate degrees of
brightness or loudness
– However, perceptions and
interpretations of sensory input can
vary considerably across cultures
– Cultural traditions affect opportunities
for experiences, which in turn
influences perceptual development
Learning Objectives
• How does the development of attention occur
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during childhood?
What characterizes the developmental
disorder attention deficit hyperactivity
disorder (ADHD)?
How is ADHD treated?
The Child
• Sensory and perceptual development is
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largely complete at the end of infancy and
becomes more refined during childhood
During childhood, sensory and perceptual
development are largely a matter of children
learning to use their senses more intelligently
Perceptual development and cognitive
development are integrated
The Child – The Development of Attention
• Perceptual development during childhood is
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the development of attention
– The focusing of perception and attention
upon something in particular
Infants are “captured by” something – they
react to environmental events
– They have an “orienting system”
Children are “directed toward” something
– They have a focusing system that seeks out
and maintains attention to events
The Child – Longer Attention Span
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Children have short attention spans
– In a study of sustained attention (Yendovitskaya,
1971),
• Children ages 2 to 3 worked for an average of
18 minutes and were easily distracted
• Children ages 5 to 6 often persisted for 1 hour or
more
Improvements in sustained attention occur from ages
5-6 to ages 8-9 as the parts of the brain involved with
attention become further myelinated
Beyond ages 8-9, there is little increase in the length
of children’s sustained attention
– But become more accurate on tasks requiring
sustained attention over the next few years
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The Child – More Selective and Systematic
Attention
Infants are not good at selective attention –
deliberately concentrating on one thing while
ignoring something else
Significant increase in focused attention between
3½ and 4 years
– However, distractions will interfere with
completion of tasks
In a research study (Vurpillot, 1968), children
aged 4-5 were not systematic in a visual search,
but most children older than 6 were very
systematic
Improvements in visual search continue to be
made throughout childhood and into early
adulthood
The Child – Problems of Attention
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Attention deficit disorder (ADHD) is characterized
by three symptoms
– Inattention
• Does not seem to listen, is easily distracted,
has trouble following instructions, does not
complete tasks, tends to be forgetful and
unorganized
– Impulsivity
• Acts before thinking and cannot inhibit urges
to blurt or to take a turn
– Hyperactivity
• Restless and fidgety
The Child – Problems of Attention
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Between 5-9% of school-age children meet the
diagnostic criteria for ADHD
Twice as many boys as girls seem to have ADHD
– Girls may be under diagnosed
Because hyperactivity is more easily observable,
children with predominantly hyperactivity/
impulsivity symptoms are diagnosed around age 8
Children with predominantly inattention symptoms
are diagnosed two years later
The inattentive subtype of ADHD is roughly twice
as common as the hyperactive-impulsive subtype
The Child – Developmental Course of ADHD
• When the predominant symptom is
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hyperactivity/impulsivity, infants are very active
and have difficult temperaments and irregular
feeding and sleeping patterns
Preschoolers must be evaluated in relation to
developmental norms for activity levels
By the grade-school years, children with
ADHD are fidgety, restless, and inattentive to
schoolwork
The Child – Developmental Course of ADHD
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An estimated 20% of ADHD children outgrow their
overactive behavior
Adolescents with ADHD continue to have difficulty
concentrating on school work and often perform
poorly in school or drop out, and behave
impulsively
In early adulthood, individuals with ADHD have
lapses of concentration, procrastinate, and make
impulsive decisions
The more severe the ADHD and associated
problems such as aggression in childhood, the
more likely it is that later life outcomes will be poor
The Child – Suspected Causes of ADHD
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ADHD possibly results from deficiencies in
executive functions controlled by the frontal lobes
of the brain
– Difficulty in inhibiting and regulation behavior
– Low levels of dopamine and norepinephrine
may be the cause of executive function
impairments
Genes predispose some individuals to develop
ADHD
Environmental factors may influence whether a
genetic predisposition develops into ADHD and
whether the individual adapts well or poorly
The Child – Treatment of ADHD
• Many children with ADHD are treated with
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stimulant drugs (i.e., Ritalin) in order to
increase levels of dopamine and facilitate
attention
– Controversy about possible overprescription
of stimulants and about side effects
Results of a multimodal treatment of attention
deficit hyperactivity disorder study (MTA):
medication alone was more effective than
behavioral treatment alone or routine care in
reducing ADHD symptoms
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Learning Objectives
How does the capacity for attention change
during adolescence?
How can hearing loss be minimized across
the lifespan, beginning with adolescence?
What changes occur in visual capabilities and
visual perception during adulthood?
What changes in auditory capabilities and
speech perception occur during adulthood?
What changes occur in taste and smell, and
in sensitivity to touch, temperature, and pain
during adulthood?
The Adolescent – Attention
• The ability to sustain attention improves
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considerably between childhood and
adulthood
– Result of increased myelination that
speeds up transmission of neural impulses
Adolescents are more efficient at ignoring
distractions in order to concentrate
Adolescents can divide their attention
systematically between two tasks
The Adolescent – Hearing
• Exposure to sounds above 75 decibels can
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result in hearing loss
– Rock concerts and club music – 120 to 130
decibels
– Most common outcome is tinnitus – ringing
sounds in one or both ears
Teens do not believe that hearing loss is a
serious health concern for them
– Hearing protection is not cool
The Adolescent – Taste and Smell
• Changes in taste during adolescence
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– Slight decline in preference for sweets and
an increased sensitivity to sour tastes
– Adolescents are more likely to have an
acquired taste for previously disliked or
avoided foods
Sense of smell in adolescence
– Women generally demonstrate greater
sensitivity than men to a variety of odors
(including body odor)
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The Adult
Sensory and perceptual capacities decline gradually
in normal adults
– Declines may begin in early adulthood, become
noticeable in 40s, and are typical by age 65 and
older
– Typically we can compensate for the deficits
Losses take two forms
– Sensory thresholds are higher
• Sensitivity to very low levels of stimulation is
lost
– Perceptual abilities decline in some aging adults
• Difficulty in processing or interpreting sensory
information
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The Adult – Vision
Aging brings changes to all components of the
visual system – pupils, lens, and retina
– Pupils become smaller and do not respond as
much when lighting conditions change
• Sharp drop in visual acuity when contrast is
poor and light levels are low
• Dark adaptation occurs more slowly
– The lens becomes denser and less flexible
• Cannot accommodate to bring objects at
different differences into focus
• Thickening of the lens results in presbyopia,
decreased ability to accommodate objects
close to the eye
Caption: Visual acuity of older adults under optimal (high
contrast and bright light), average (low contrast and
bright light), and poor (low contrast and low light)
stimulus conditions
The Adult – Vision
– The effects of age-related changes in the lens
• Visual acuity steadily declines in old age,
but typically the implications are minor
– In one major study, three out of four
older adults (75 years and older) had
good corrected vision
– Women experience greater declines in
visual acuity than men and become
susceptible to falls, fractures, and loss of
independence
– Non-corrected poor visual acuity (20/40
or worse) is an impairment that reduces
older adults’ quality of life
The Adult – Vision
– Age-related macular degeneration (AMD)
results from damage to retinal cells
responsible for central vision
• Vision becomes blurry and begins to
fade from the center of the visual field –
blank or dark space in the center of the
image
• Leading cause of blindness in older
adults
• Causes are unknown and there is no
cure
The Adult – Vision
– Changes in the retina also lead to decreased
visual field or loss of peripheral vision
• Loss of peripheral vision leads to tunnel
vision, caused by retinitis pigmentosa (RP)
or by glaucoma
– Retinitis pigmentosa is a group of
hereditary disorders that involve gradual
deterioration of the light-sensitive cells of
the retina
– Glaucoma is caused by increased fluid
pressure in the eye that can damage the
optic nerve, cause loss of peripheral
vision, and lead to blindness
Caption: How a scene might be viewed by someone with
various eye conditions: A) cataracts, B) glaucoma, (C
diabetes retinopathy, D) age-related macular
degeneration, and E) retinitis pigmentosa
The Adult – Attention and Visual Search
• Older adults are less able to divide attention
between two tasks or to selectively attend to
stimuli while ignoring distractors
– Older adults have the greatest difficulties in
processing visual information when the
situation is novel (when they are not sure
exactly what to look for or where to look)
and when it is complex (there are many
distractions)
The Adult – Hearing
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Among older adults, hearing impairments are
three times as prevalent as visual impairments
– Among adults aged 65 and older, as many as
90% have mildly impaired hearing that
progressively worsens with age
– Most age-related hearing problems originate in
the inner ear
• Auditory receptors and hearing-related
structures and neurons degenerate during
adulthood and result in presbycusis
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The Adult – Hearing
The most common form of presbycusis is loss of
sensitivity to high-frequency or high-pitched sounds
– Results in difficulty hearing a child’s high voice,
the flutes in an orchestra, or high-frequency
consonant sounds such as s, z, and ch
– After age 50, it also becomes difficult to hear
lower-frequency sounds
To be heard by an average older adult, a sound must
be louder than the level needed by a younger adult
Men show detectable hearing losses earlier in life
than women and lose hearing sensitivity at a faster
rate than women
– Men who work in noisy industrial conditions
experience more hearing loss than other men
The Adult – Speech Perception
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Speech perception is dependent on the ability to hear
and upon cognitive processes such as attention and
memory
To understand conversation,
– Listening conditions are important; background
noise is problematic
– Increased attentional demands (divided attention)
are problematic
Auditory perception is more difficult when the tasks
are novel and complex, and the listening conditions
are poor
– Familiar conditions allow use of contextual cues
The Adult – Aging of the Chemical Senses
• General decline in sensitivity to taste
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– Older men have somewhat greater decline
than older women
– But great variability in individual
experiences
Ability to perceive odors typically declines
with age
– Health adults retain their sense of smell
better than those have diseases, smoke, or
take medications
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The Adult – Touch, Temperature, and Pain
Sensitivity for touch is gradually lost from middle
childhood, but may not have implications for daily life
Older people may be less sensitive to changes in
temperature than younger adults
Compared to younger adults, older adults appear to
be less sensitive to weak levels of pain but are not
less sensitive to stronger pain stimuli
– Older adults are more likely to experience chronic
pain than younger adults, but are less likely to
obtain adequate pain relief
– Treating painful conditions and providing effective
pain relief could improve the daily functioning and
psychological well-being of older adults
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The Adult in Perspective
During adulthood, changes in sensation and perception
of visual and auditory capacities are the most important
and the most universal
– Senses become less sharp and are used less
effectively
Many sensory declines can be compensated
Older adults with two or more sensory impairments are
likely to experience difficulty with basic tasks of living
– Usually have physical or intellectual impairments,
too, probably due to general declines in neural
functioning that affect both perception and cognition
However, most older adults, even those with sensory
impairments, are engaged in a range of activities and
are living full lives