Perceptual DevelopmentPerceptual Development

Chapter 5 OBJECTIVES:

What senses do newborn babies have?Do their senses work like adults?

How do Infants perceive the world?

The The SensesSenses begin to begin to function early in life. But function early in life. But

how can we actually know how can we actually know what an infant senses?what an infant senses?

Since infants can’t tell us, researchers have devised ways to find out.

SensationSensation

To understand what an infant can sense researchers often present two stimuli and record the baby’s response.

‐ For example a baby is given a sweet tasting substance and a sour tasting substance

If the baby consistently responds differently to the two stimuli then the infant must be able to distinguish between them.

A technique called A technique called HabituationHabituation is often used in is often used in

researching infant preferenceresearching infant preference

This is the process of getting used to something.

Click on the baby to view a video clip

(also provided in your textbook DVD)

Can infants use their Can infants use their senses like adults?senses like adults?

NO, we do not arrive with all of our senses fully functioning. This is yet another area that will develop and

mature with the infant.

SmellSmellInfants have a keen sense of smell and respond positively to pleasant smells and negatively to unpleasant smells (Menella, 1997).

‐ Honey, vanilla, strawberry, or chocolate: relaxed, produces a contented-looking facial expression

‐ Rotten eggs, fish, or ammonia produce exactly what you might expect…infants frown, grimace or turn away

Did you know…Did you know…Young infants recognize familiar odors

Newborns will turn toward of a pad that is:

‐ Saturated with their own amniotic fluid

‐ Saturated with their own mother’s milk or her perfume (Porter & Winburg, 1999).

‐ Isn’t that amazing?

TasteTaste

Newborns also have a highly developed sense of taste. They can differentiate salty, sour, bitter & sweet tastes (Rosenstein, 1997).

Do you think infant’s have a favorite taste?

TasteTasteMost infants seem to have a “sweet tooth”.‐ Infants will nurse more after their mother

has consumed a sweet-tasting substance like vanilla (Menalla, 1997)

Newborns prefer sweet. However, at 4 months, infants will have a salty preference

‐ They will start liking salt which was aversive to them as newborns.

TouchTouch

Newborns are sensitive to touch, many areas of the newborn’s body respond reflexively when touched

What do YOU think?‐ If babies react to touch, do they

experience pain?

OUCH!?OUCH!?The infant’s nervous system is definitely capable of experiencing pain

Receptors for pain in the skin are just as plentiful in infants as they are in adults.

Babies behavior in response to a pain-provoking stimulus suggests that they experience pain.

What Do Infants See?What Do Infants See?

Vision is the least mature of all the senses at birth because the fetus has nothing to look at, so visual connections in the brain can’t form until birth.

Newborn visual acuity is 20/400 to 20/800‐ 20/200 or worse defines legal blindness in adults

Newborn visual acuity is 20/400 to 20/800‐ 20/200 or worse defines legal blindness in adults

By 6 months, infant visual acuity is 20/25

By 1 year, infant visual acuity is at adult levels (20/20)

Click on the baby to see like an infant!

What is the clarity of infant What is the clarity of infant vision and how can we vision and how can we

measure it?measure it?Visual acuity is defined as the smallest pattern that can distinguished dependably.

‐ Infants prefer to look at patterned stimuli instead of plain, non-patterned stimuli

To estimate an infant’s visual acuity, we pair gray squares with squares that differ in the width of their stripes.

When the infant looks at the two stimuli When the infant looks at the two stimuli equally long, it indicates they are no equally long, it indicates they are no

longer able to distinguish the stripes of longer able to distinguish the stripes of the patterned stimulus from the solid gray the patterned stimulus from the solid gray

squaresquare

At birth, infants’ sensitivity to fine, high-spatial frequency gratings, like their acuity, is very poor but improves steadily with age.

Light SensitivityLight SensitivityNewborns begin to see the world not only with greater acuity but also in color

At birth, infants have the greatest sensitivity to intermediate wavelengths (yellow/green) and less to short (blue/violet) or long (red/orange).

Newborns can perceive few colors, but By 3-4 months newborns are able to see the full range of colors (Kellman, 1998).

‐ In fact, by 3-4 months infants have color perception similar to adults (Adams, 1995).

At 1 week, the infant can discriminate the desaturated red from gray

At 2 months, the infant can discriminate the desaturated blue from gray

What do babies hear?What do babies hear?Hearing is the most mature sense at birth. In fact, some sounds trigger reflexes even without conscious perception.

‐ The fetus most likely heard these sounds in the womb during last trimester

Sudden sounds startle babies-making them cry, some rhythmic sounds, like a heartbeat/lullaby put a baby to sleep.

Yes, infants in first days of life, turn their head toward source of sounds and they can distinguish voices, language, and rhythm.

Auditory ThresholdAuditory ThresholdThe fetus can hear in utero at 7-8 months, so it is no surprise that newborns respond to auditory stimuli but, do infants hear as well as adults??

No they cannot. The Auditory threshold refers to the quietest sound that a person can hear.

The quietest sound an newborn responds to is about 4 times louder than the quietest sound an adult responds to.

Do infants hear like adults?Do infants hear like adults?Research reveals that adults hear better than infants because adults can hear some very quiet sounds that infants cannot.

Research shows that infants hear sounds best that have high pitches in the range of human speech (Jusczyk, 1995).

‐ Can differentiate vowels from consonants‐ At 4 months, can recognize own name

Infants also use sound to locate objects and estimate distance.

How DO Infants How DO Infants Perceive the World?Perceive the World?

Perceptual Constancies Perceptual Constancies

An important part of perceiving objects is that the same object can look very different

Infants master size constancy very early on

‐ They recognize that an object remains the same size despite its distance from the observer

You can recognize that the You can recognize that the woman in this picture has woman in this picture has

not shrunk…she is just not shrunk…she is just farther awayfarther away

Depth PerceptionDepth PerceptionInfants are not born with depth perception, it must develop. The images on the back of our eyes are flat and 2-dimensional

To create a 3-D view of the world, the brain combines information from the separate images of the two eyes, retinal disparity

Visual experience along with development in the brain lead to the emergence of binocular depth perception around 3-5 months of age

Perception in infants Perception in infants Can infants process sensory information accurately?

This was a question posed by Walk and Gibson in 1960

The Visual cliff experiment was designed to provide the illusion of a sudden drop off between one horizontal surface and another

Face RecognitionFace Recognition

Infants enjoy looking at faces, a preference that may reflect innate attraction to faces, or a fact that faces may attract infant’s attention.

At birth, infants are attracted to the borders of objects When looking at a human face

‐ a newborn will pay more attention to the hairline or the edge of the face (even though the newborn can see the features of the face)

By 2 months of age, infants begin to attend to the internal features of the face – such as the nose and mouth

By 3 months of age, infants focus almost entirely on the interior of the face, particularly on the eyes and lips. At this age, infants can tell the difference between mother’s face and a stranger’s face.

Theorist’s believe that infants are attracted to human faces because faces have stimuli that move (eyes and lips) and stimuli with dark and light contrast (the eyes, lips and teeth).

Infants readily look at faces, Infants readily look at faces, a preference that may reflect a preference that may reflect an innate attraction to faces an innate attraction to faces or the fact that faces have or the fact that faces have

many properties that attract many properties that attract infant’s attentioninfant’s attention

Perceiving FacesPerceiving FacesInfants are particularly interested in looking at human faces, but focus on different areas of the face depending on their age

Motor Motor DevelopmentDevelopment

Test your KnowledgeTest your Knowledge

Pedal a tricycle

Sit without support

Walk unassisted

Stand on one foot for 10 seconds

Roll over

Kick a ball forward

Crawl

At what age can at least 50% of children begin to display each of these behaviors?

How Did You Do?How Did You Do?Pedal a tricycle 2 years, 90% by 3yearsSit without support6 Months, 90% by 7-8 months. Walk unassisted12 Months, 90% by 14 months.Stand on one foot for 10 seconds4 ½ years

Roll over 3 months, 90% by 5 months.Kick a ball forward20 months, 90% by 9 months.Crawl7 months, 90% by 9 months

Motor MilestonesMotor Milestones50 percent 90 percent

Roll over 3.2 months 5.4 months

Grasp rattle 3.3 months 3.9 months

Sit without support 5.9 months 6.8 months

Stand holding on 7.2 months 8.5 months

Pincer grasp 8.2 months 10.2 months

Crawl 7.0 months 9.0 months

Stand alone 11.5 months 13.7 months

Walks well 12.3 months 14.9 months

Build tower (2 cubes)

14.8 months 20.6 months

Walk steps 16.6 months 21.6 months

Jump in place 23.8 months 2.4 years

Copy circle 3.4 years 4.0 years

Head ControlHead ControlAt birth infants can turn their heads from side to side while lying on their backs

By 2-3 months they can lift their heads while lying on their stomachs

By 4 months infants can keep heads erect while being held or supported in a sitting position

Before you walk, you must learn Before you walk, you must learn to….to….

At around 6-8 months, infants become capable of self-locomotion

To master walking (around 13-14 months), infants must acquire distinct skills

‐ Standing upright‐ Maintaining balance‐ Stepping alternately‐ Using perceptual information to evaluate

surfaces

CrawlingCrawlingBegins as belly-crawling‐ The “inchworm belly-flop” style

Most belly crawlers then shift to hands-and-knees, or in some cases, hands-and-feet

Some infants will adopt a different style of locomotion in place of crawling such as bottom-shuffling while some infants skip crawling altogether

Due to the “back-to-sleep” movement, infants spend less time on their tummies which may limit their opportunity to learn how to propel themselves

Belly-crawling

Hands-and-feet crawling

Hands-and-knees crawling

Walking – SteppingWalking – SteppingChildren do not step spontaneously until approximately 10 months because they must be able to stand in order to step

Maintaining balance when transferring weight from foot to foot seems to be key

Thelen and Ulrich (1991) found that 6- and 7-month-olds, if held upright by an adult, could demonstrate the mature pattern of walking of alternating steps on a treadmill

Gross motor skillsGross motor skillsEmerge directly from reflexes.

These are physical abilities involving large body movements and large muscle groups such as walking and jumping.

Involve the movement of the entire body-‐ Rolling over, standing, walking

climbing, running

Fine Motor SkillsFine Motor SkillsAfter infancy fine motor skills progress rapidly and older children become more dexterous because these movements involve the use of small muscle groups

These consist of small body movements, especially of the hands and fingers.

‐ such as drawing, writing your name, picking up a coin, buttoning or zipping a coat.

HandednessHandednessYoung babies reach for objects without a preference for one hand over the other

The preference for one hand over the other becomes stronger and more consistent during preschool years

‐ By the time children are ready to enter kindergarten, handedness is well established and very difficult to reverse

Handedness is determined by heredity and environmental factors‐ Approximately 10% of children write left-handed