A baby's senses of touch, taste, smell, hearing and vision begin to develop well before birth. According to Dr. Stanley Graven, a University of South Florida professor specializing in neonatal brain development, all five senses develop at around the same time because the sensory organs are coordinating systems. Graven further states that appropriate environmental stimuli in early infancy can promote healthy sensory development. A controlled stimuli environment is particularly important in preterm infants.
Touch and Reflex
The tactile sensory system controls touch and reflexes. A fetus has functional nerve endings by about 11 weeks after conception and begins to exhibit reflexive behaviors by 26 weeks. Sensitivity and reflexive action is most advanced around the mouth, or perioral area, a function that is crucial to survival. Rooting and suckling are among a baby's first movements.
Taste and Feeding
Taste is a function of the gustatory system. The mouth and tongue are fully formed 8 weeks after conception. Starting at around week 20, the fetus begins to develop taste buds and reacts to bitter tastes by 28 weeks. At 3 to 6 days old, a newborn baby can differentiate between breast milk and formula.
According to the Infant and Toddler Connection of Virginia, or ITCV, the fetus consumes about a liter of amniotic fluid per day while in utero; this is why the expectant mother's diet affects fetal health and development. This consumption of fluids also prepares the baby for the swallowing and breathing patterns used in feeding.
Smell
The olfactory system controls the sense of smell. A fetus's nose forms by 8 weeks. The ITCV states that the sense of smell "is one of the most well-developed senses" in a newborn because it contributes to survival functions such as identifying the mother, locating the food source and sensing danger. Because the olfactory and gustatory systems are closely connected, over-stimulation of the olfactory system through exposure to strong smells can affect an infant's feeding patterns.
Hearing
The auditory system controls hearing and aids in attention, learning and speech. The ear is functional in utero by 24 weeks. Amniotic fluid conducts sound, so the fetus can hear sounds outside the womb. Exposure to some loud noises, such as a rock concert, may cause discomfort due to over-stimulation, while long-term or extreme noise exposure in utero can damage the baby's hearing.
Vision
The visual sensory system is the most complex and takes the longest to fully form. Eye formation begins by day 22 in utero, but the eyes do not open until 7 months. The eyes continue to develop after birth until about 3 to 4 months. The visual and tactile systems are closely related, and this connection is important to the development of motor skills.
