Chapter 4 – Infancy: Sensation, Perception, and Learning
Neonates: Newborn babies, their noses, ears and entire heads often bear the
marks of the pressures exerted on them as they passed through the birth canal.
Their skin is often red, wrinkled, and blotchy, partly as a result of floating for nine
months in the amniotic fluid. Their heads are oversized in proportion to their
bodies, and their little legs appear weak, even useless, most of these
characteristics disappear even before the neonate period of three to four weeks is
A new baby's reflexes
− Reflex: A human's involuntary response to external stimulation. Reflexes
are some of the first behaviours to appear in a new born, some of which are
permanent , others disappear during the first year of life, and in some cases
these are replaced by voluntary behaviours that baby learns early in life.
Abnormalities in a baby's reflexes during the first days or weeks after can be
useful indicators for identifying visual and hearing problems.
Infant state: A recurring pattern of arousal in the newborn, ranging from alert,
vigorous, wakeful activity to quiet, regular sleep. Internal forces play a central role
in infant states and their changes.
− Sleep: The newborn on average sleeps about 70 percent of the time in a
series of long and short naps during the day and night. By 4 weeks a baby's
period of sleep tend to be fewer but longer and by 8 weeks the baby sleeps
more during the night and less during the day. The infant becomes less
fussy as it gains control over its states of arousal.
Sudden infant death syndrome: SIDS refers to the sudden and unexpected
death of an otherwise apparently healthy infant under 1 year of age. The death
usually remains unexplained after all known and possible causes of death have
been ruled out.
REM and non-REM sleep: Rapid-eye movement (REM) sleep is characterized by
rapid, jerky movements of eyes and, in adults, is often associated with dreaming;
infants spend 50 percent of their sleep in REM activity, whereas adults spend only
about 20 percent. This activity is absent in the remaining non-REM sleep. Even
though infants have REM sleep there is no real way of knowing if infants dream. If
people are prevented from obtaining REM sleep they tend to be irritable and
disorganized during their later waking hours.
Autostimulation theory: The theory that during REM sleep the infant's brain
stimulated itself and this this, in turn, stimulates early development of the central
nervous system. If this theory is right, the speed with which infants reduce their
percentage of REM sleep could depend on how much external stimulation they
receive. Crying: Three different types of crying, reflective of the infant’s varying needs,
have been identified.Most mothers can distinguish between these types of cries
but only when they are listening to their own babies, men are less skilled than
women and non-parents are less skilled than parents.
− Basic: Linked to hunger, among other factors. Starts arrhythmically and at
low intensity; gradually becomes louder and more rhythmic; sequence is
− Angry: Same as basic pattern except that segments of crying, resting, and
inhaling vary in length, and crying segments are longer. Causes include
removal of a pacifier or toy.
− Pain: Sudden in onset, loud from the start, and made up of a long cry
followed by a series of short, gasping inhalations. Causes include discomfort
from soiled diaper, a pin prick, or stomach pain.
Colic: A prolonged period of unexplained crying in an infant, occurs in roughly 20
percent of infants, usually begins between 2 and 4 weeks of age and its causes
are not known. In most cases, it stops by the time the baby is 3 or 4 months of
age. Colic is usually harmless but in some cases it may indicate an illness, such as
a hernia or an ear infection.
How to soothe an infant
− Infants soothe themselves: One way infants soothe themselves is by
sucking, which the baby routinely engages in, even while still in the utero.
The soothing techniques that work change as the infant develops. Sucking
on a sweet liquid appears to be effective in calming a 2 week old baby, but
less effective for a 4 week old baby unless accompanied by eye contact with
− Parents soothe their babies: A variety of techniques are effective in
soothing, including rocking, swaddling and massaging. In swaddling, a baby
is wrapped tightly in a blanket or cloth, thus keeping her arms and legs
immobile. Swaddling has been used successfully in hospital nurseries
throughout North America and in may cultures around the world.
Evaluating the Newborn's Health and Capabilities
To find out about the health, maturity, and the capabilities of the newborn, tests of
baby's reflexes may be combined with other assessment techniques.
− Brazelton Neonatal Assessment Scale: One of the most widely used
tests for newborns. A scale used to measure an infant’s sensory and
perceptual capabilities, motor development, range of states, and ability to
regulate these states. The scale also indicates whether the brain and the
central nervous system are properly regulating autonomic responsivity. It is
used to identify infants at risk for developmental problems, and it can aid in
diagnosing neurological impairment.
The infant's Sensory and Perceptual Capacities
Researchers have discovered that babies' sensory and perceptual capabilities are
quite well developed even at birth, allowing infants to begin adapting immediately to the environment.
− Sensation: The detection of stimuli by the sensory receptors (eyes and
− Perception: The interpretation of sensations in order to make them
Unlocking the Secrets of Babies' Sensory Capabilities
To study an infant's sensory capabilities researchers have relied on information
from the autonomic nervous system, which controls involuntary bodily function as
heart rate and berthing. For instance, a change in a baby's breathing following a
change in the pitch of a sound suggest that the infants heart the pitch change.
− Violation-of-expectation: a technique used to study infants, it introduces an
unusual or impossible sight, such as an object floating in space. If, upon
seeing this information, the baby responds by altering his behaviour (by
slowing down or stopping his rate of sucking), it suggests that the baby
knows something about objects normally work.
− Visual Preference Method: A method of studying infants; abilities to
distinguish one stimulus from another by measuring the length of time they
spend attending to different stimuli. The researcher presents an infant with
two stimuli, if an infant looks longer at one stimuli than at the other, we can
assume that she can distinguish between the two stimuli.
− Habituation: The process by which an individual reacts with less and less
intensity to a repeatedly presented stimulus, eventually responding only
faintly or not at all. Habituation is widely used to explore infants' sensory
and perceptual capabilities.
Hearing: Babies Are Good Listeners
An infant's hearing can be tested shortly after birth and these tests show that
newborn's hearing is extremely well developed, although it is not as developed as
adults. For a newborn, a sound must be louder—about 10 to 17 decibels louder—
than the sound that an adult can detect. Babies are less sensitive to low pitched
sounds; they are more likely to hear a sound that is high in pitch. Over the first
two years babies rapidly improve in their ability to discriminate sounds of different
pitches, until they eventuall