CHAPTER 6SENSATION, 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– 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 assessed?

• What are infants’ visual capabilities?

• What sorts of things do infants prefer to look at?

The Infant – Assessing Sensory and Perceptual Abilities

• The main methods used to study infant perception– Habituation– Preferential looking– Evoked potentials– Operant conditioning

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

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

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

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

• Caption: What the young eye sees

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

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)

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

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 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 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 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

• 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

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 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

• 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

• 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 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

• 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 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 during childhood?

• What characterizes the developmental disorder attention deficit hyperactivity disorder (ADHD)?

• How is ADHD treated?

The Child

• Sensory and perceptual development is 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 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

• 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

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

• 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

• 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 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

• 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

• 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 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

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 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 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– 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)

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

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

• 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

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

• 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– 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

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

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