Taste is a chemical sense that allows humans to process information
through different sensations—such as sweet or salty—as well as
textures. (Robert J. Huffman/Field Mark Publications)
Movement Sensations
The movement sensations, or vestibular system,
is a sensory area that is not often discussed in litera-
ture but is important to development. The vestibular
system involves one’s balance and works in conjunc-
tion with other senses. The vestibular system is de-
signed to answer questions that relate to the human
body, such as ‘‘Which way is up?’’ and ‘‘Where am I
going?’’ This is accomplished by measuring the posi-
tion of the head through the combined efforts of the
five sensory organs in the inner ear, a process that en-
ables one to maintain one’s balance.
During gestation, the vestibular system is imma-
ture but operating by the ninth week and continues
to mature throughout gestation and after birth. The
vestibular system is important for an infant to be able
to hold its head steady when being held upright, sit-
ting up, standing, and walking. It is easy to recognize
when the vestibular system is sending different mes-
sages to the brain than what is actually taking place.
Examples include infants falling over when sitting
and falling down when walking. In these instances,
the vestibular system is sending a different message
to the infant’s brain in relation to what is happening
with its body.Auditory System
The auditory system begins to develop next.
Around the fifth week of gestation the ear begins to
form, and by the twenty-fourth week of gestation all
hearing structures are in place. By the end of gesta-
tion, the auditory system is reasonably mature and
continues to develop throughout the first year after
birth. Infants demonstrate this sense by turning their
head or eyes toward a sound. Newborns are more
likely to respond to higher frequencies than lower fre-
quencies. Also, repetition and longer duration in-
crease the likelihood of infants hearing and
responding to a sound. Adults can encourage infant
stimulation through musical toys that use repetitive
sounds and higher pitched tones.Visual System
The visual system begins to develop around the
ninth and tenth week of gestation and continues de-
veloping until three years after birth. At birth, infants
are able to detect motion, can focus on an object
about eight inches away, are sensitive to brightness,
and have red and green color vision. By the end of the
second month, infants are able to track smooth pat-
tern movements and begin to discriminate between
colors. During the third month, infants are better able
to focus on objects farther away and are beginning to
develop depth perception, both of which continue to
develop until age two or three. Many toy companies
gear toys that have geometric shapes and are black
and white for newborns, and toys that are brightly col-
ored and have patterns for infants about three
months and older. These toys encourage develop-
ment as the infant’s neuronal pathways are being
established.Body Position Sense
The seventh sense, body position sense, or pro-
prioception, works in conjunction with other senses.
Proprioception is the movement and position of the
limbs and body in relation to space. Proprioceptors
are located in muscles and joints and are triggered by
bodily movements. Proprioceptors, combined with vi-
sion, the sense of touch, and input from the vestibular
system, help infants reach such milestones as rolling
over, crawling, and walking.356 SENSORY DEVELOPMENT