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.
Sensation
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
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 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.
Smell
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?
Taste
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?
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.
Touch
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!?
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?
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
gray
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 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
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?
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 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
observer
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
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 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
2 years, 90% by 3years
Sit without support
6 Months, 90% by 7-8
months.
Walk unassisted
12 Months, 90% by 14
months.
Stand on one foot for 10
seconds
4 ½ years
Roll over
3 months, 90% by 5
months.
Kick a ball forward
20 months, 90% by 9
months.
Crawl
7 months, 90% by 9
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
3.4 years
4.0 years
Copy circle
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
position
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
Crawling
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 bottomshuffling 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-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 7month-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,
running
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.
Handedness
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