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					Perceptual Development
      Chapter 5 OBJECTIVES:

What senses do newborn babies have?
  Do their senses work like adults?
 How do Infants perceive the world?
  The Senses begin to function early
   in life. But how can we actually
    know what an infant senses?

Since infants can’t tell us, researchers have
         devised ways to find out.
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 Habituation is
often used in researching infant

This is the process of getting used to
Click on the baby to view a video clip
  (also provided in your textbook DVD)
 Can infants use their senses like

  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.
Infants 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…
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?

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?
Most 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.

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?
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
        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 vision and
      how can we 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 equally
   long, it indicates they are no longer able to
distinguish the stripes of the patterned stimulus
             from the solid gray square
   At birth, infants’ sensitivity to fine, high-spatial
frequency gratings, like their acuity, is very poor but
              improves steadily with age.
              Light Sensitivity
Newborns 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
          What do babies hear?
Hearing is the most mature sense at birth. In fact,
some sounds trigger reflexes even without conscious

‐ 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 Threshold
The 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

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?
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
How DO Infants Perceive
     the World?
      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
You can recognize that the woman
in this picture has not shrunk…she
         is just farther away
             Depth Perception
Infants 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
           Can infants process
           sensory information

           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
           Face 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, a
preference that may reflect an innate
 attraction to faces or the fact that
  faces have many properties that
      attract infant’s attention
           Perceiving Faces
Infants are particularly interested in looking at
human faces, but focus on different areas of
the face depending on their age
Motor Development
           Test your Knowledge
At what age can at least 50% of children begin to
        display each of these behaviors?

Pedal a tricycle           Roll over

Sit without support        Kick a ball forward

Walk unassisted            Crawl

Stand on one foot for
10 seconds
             How Did You Do?
Pedal a tricycle           Roll over
2 years, 90% by 3years
                           3 months, 90% by 5
Sit without support
6 Months, 90% by 7-8
months.                    Kick a ball forward
Walk unassisted            20 months, 90% by 9
12 Months, 90% by 14       months.
Stand on one foot for 10   Crawl
seconds                    7 months, 90% by 9
4 ½ years                  months
                Motor Milestones
                        50 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 Control
At 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
 Before you walk, you must learn 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
Begins 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

Hands-and-knees crawling

             Hands-and-feet crawling
        Walking – Stepping
Children 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 skills
Emerge 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,
          Fine Motor Skills
After 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.
Young 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