30 From Reflexes to Voluntary Movements

Martha Lally; Suzanne Valentine-French; and Dinesh Ramoo

Newborns are equipped with a number of reflexes (Table 3.1) which are involuntary movements in response to stimulation. Some of the more common reflexes, such as the sucking reflex and rooting reflex, are important to feeding. The grasping and stepping reflexes are eventually replaced by more voluntary behaviours. Within the first few months of life these reflexes disappear, while other reflexes, such as blinking, swallowing, sneezing, gagging, and withdrawing stay with us as they continue to serve important functions. Reflexes offer pediatricians insight into the maturation and health of the nervous system. Reflexes that persist longer than they should can impede normal development (Berne, 2006). In preterm infants and those with neurological impairments, some of these reflexes may be absent at birth. Once present, they may persist longer than in a neurologically healthy infant (El-Dib, Massaro, Glass, and Aly, 2012).

Table 3.1: Some Common Infant Reflexes
Reflex Description Image
Sucking Sucking on anything that touches their lips A baby sucking on its fingers
Rooting Turning their head when their cheek is touched A baby smiling as he is kissed on the check by his dad
Grasp Fingers automatically grip anything that touches the palm of their hand A baby grasping an adult's finger
Babinski Toes will fan out and curl when the sole of the foot is stroked from heel to toe A baby curling its toes
Moro A sudden noise or loss of support to their head and neck will cause them to spread out their arms and legs, then quickly contract the limbs inward A baby stretching its arms out
Tonic Neck When lying on their back with the head to one side, they will extend their arm and leg on that side while flexing the limbs on the opposite side (looks like a fencer pose). A baby displaying the tonic reflex
Stepping Moving their legs in a stepping-like motion when their feet touch a smooth surface A baby stepping while being held by an adult

Motor Development

Motor development occurs in an orderly sequence as infants move from reflexive reactions (such as sucking and rooting) to more advanced motor functioning. As mentioned in the prenatal section, development occurs according to the cephalocaudal (from head to tail) and proximodistal (from the midline outward) principles. For instance, babies first learn to hold their heads up, then to sit with assistance, then to sit unassisted, followed later by crawling, pulling up, cruising, and then walking. As motor skills develop, there are certain developmental milestones that young children should achieve. For each milestone there is an average age, as well as a range of ages in which the milestone should be reached. An example of a developmental milestone is a baby holding up its head. On average, babies are able to hold up their head at six weeks old, and 90 percent of babies achieve this between three weeks and four months old. If a baby is not holding up his head by four months, they are showing a delay. On average, most babies sit alone at seven months old. Sitting involves both coordination and muscle strength, and 90 percent of babies achieve this milestone between five and nine months old. If the child is displaying delays on several milestones, that is reason for concern, and the parent or caregiver should discuss this with the child’s pediatrician. Some developmental delays can be identified and addressed through early intervention.

Motor skills refer to our ability to move our bodies and manipulate objects. Fine motor skills focus on the muscles in our fingers, toes, and eyes, and enable coordination of small actions (such as grasping a toy, writing with a pencil, and using a spoon). Newborns cannot grasp objects voluntarily but do wave their arms toward objects of interest. At about four months, the infant is able to reach for an object, first with both arms and within a few weeks with one arm. At this age, grasping an object involves the use of the fingers and palm, but no thumbs. This is known as the palmer grasp. The use of the thumb comes at about nine months, when the infant is able to grasp an object using the forefinger and thumb. Now the infant uses a pincer grasp, which greatly enhances the ability to control and manipulate an object. Infants take great delight in this newfound ability. They may spend hours picking up small objects from the floor and placing them in containers. By nine months, an infant can also watch a moving object, reach for it as it approaches, and grab it.

 

An image of a baby using the pincer grasp to hold an adult's finger
Figure 3.8: Pincer grasp

Gross motor skills focus on large muscle groups that control our head, torso, arms, and legs and involve larger movements (such as balancing, running, and jumping). These skills begin to develop first. Examples include moving to bring the chin up when lying on the stomach, moving the chest up, and rocking back and forth on hands and knees. But it also includes exploring an object with one’s feet as many babies do as early as eight weeks old if seated in a carrier or other device that frees the hips. This may be easier than reaching for an object with the hands, which requires much more practice (Berk, 2007). Sometimes an infant will try to move toward an object while crawling and surprisingly move backward because of the greater amount of strength in the arms than in the legs.


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From Reflexes to Voluntary Movements by Martha Lally; Suzanne Valentine-French; and Dinesh Ramoo is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.

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