Taste and smell are chemical senses; they process information by processing chemical changes in the air and in objects on the tongue. These are primitive sensory systems that are intimately involved with early developmental activities such as feeding, eating, and recognizing family members compared to strangers. In this way, these are protective senses; they enable the organism to survive, both through recognizing familiarity for safety purposes and by enabling the infant to identify food for nourishment.
The taste buds become apparent during the eighth week of gestation, and by the fourteenth week the taste sensation is formed. At birth, infants express positive and aversive facial responses to tastes. The sense of smell is apparent at birth as an infant begins to recognize and prefers its mother's scent. As infants begin to develop, it is important to observe their reaction to the different sensations of sweet, sour, bitter, and salty, as well as to textures, to know what they like or dislike.
The movement sensations, or vestibular system, is a sensory area that is not often discussed in literature but is important to development. The vestibular system involves one's balance and works in conjunction with other senses. The vestibular system is designed 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 position of the head through the combined efforts of the five sensory organs in the inner ear, a process that enables one to maintain one's balance.
During gestation, the vestibular system is immature 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, sitting up, standing, and walking. It is easy to recognize when the vestibular system is sending different messages 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.
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 gestation, 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 frequencies. Also, repetition and longer duration increase 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.
The visual system begins to develop around the ninth and tenth week of gestation and continues developing 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 pattern 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 colored and have patterns for infants about three months and older. These toys encourage development as the infant's neuronal pathways are being established.
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 vision, the sense of touch, and input from the vestibular system, help infants reach such milestones as rolling over, crawling, and walking.
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Once your pregnancy is over and done with, your baby is happily in your arms, and youre headed back home from the hospital, youll begin to realize that things have only just begun. Over the next few days, weeks, and months, youre going to increasingly notice that your entire life has changed in more ways than you could ever imagine.