The term "motor development" refers to age related changes in our capacity for voluntary physical movement. Although these changes occur throughout the lifespan, the most important changes for parents occur between birth and 18 years of age. What follows is a relatively brief overview of some of the most important changes, and how parents can nurture them. More detailed descriptions are available in the references cited at the end of this description. You may view less detailed milestones by clicking here.
Humans must learn a bewildering number of behaviors in order to become competent adults. As adults we take most of these behaviors for granted, but infants are confronted with a large number of problems that can only be solved by learning appropriate physical behaviors. For instance, we must learn to control our own body, including bowel movement, posture, balance, and locomotion.
Fortunately, nature provides the newborn with a large number of reflexes. These reflexes are inborn automatic responses to particular stimuli. These include the rooting, sucking, and grasping reflexes. Without such reflexes the newborn human would literally die. For instance, can you imagine what it would be like trying to teach a newborn baby to suck a nipple. What would you say? What could you tell a child who doesn't speak yet? The baby would probably die of starvation a long time before a parent could teach it to suck. And so, these inborn reflexes facilitate the baby's survival until they develop the ability to voluntarily control their own actions. What this means for infant motor development is that the first weeks of life are largely dominated by reflexive movements. Once they have done their job, many of these reflexes (but not all) fade away during the first six months of life, replaced by voluntary equivalents.
Neonates are confronted with several types of related problems when it comes to learning how to use their body. The first consists of learning that their body parts exist and belong to them. You see, the infant is born not knowing who they are, what body parts they have, or how to control them. Next, they must learn how to control each separate body part. Then they must learn how to coordinate different body parts in order to achieve their goals. And, somewhere in all of this they must make allowances for the effects of gravity upon a rapidly growing body with a changing center of gravity. The ways in which infants solve these problems is remarkably similar across all human cultures. The general pattern consists of first learning how to control the muscles at the top and center of the body followed by learning how to control the smaller muscles further from the center of the body.
Gross Motor Skills
Gross motor skills are the abilty to control the large muscles of the body. These are associated with the movement of the torso, arms and legs. Fine motor skills are the ability to move the smaller muscles of the body. These are associated with the control of the tongue and fingers. In general, gross motor skills develop before fine motor skills. This makes sense when you consider that you have to be able to control your arms in order to get your fingers to do something like button your clothes. A complete description of all of the developments that occur in this area during infancy will require more space than is available here. Instead, I will provide an overview, focusing on some of the key developments.
One of the first and most important parts of the body the newborn must gain control of is it's head. Control of the head is vital in order to direct attention. The eyes can only see what is within a certain range of vision, generally in front of the head. The importance of this for learning and language development will be discussed elsewhere. At birth however, the infant cannot yet control it's head. Part of the problem is that it doesn't even know it has a head. In addition, the head is too heavy for the newborn baby to lift. It's neck muscles are still undeveloped, and the baby does not yet know how to control them. Typically it takes the first four weeks of life for babies to learn how to control and lift their head, though some babies may take as long as five months to achieve this.
A major type of behavior that develops during infancy is reaching. At birth, infants reach without a real intention. They reach for salient stimuli, and there is no coordination of reaching and grasping. One result is that infants will reach for objects and fail to grasp them because they have not yet learned how to control or synchronize their grasping with their reaching. Between 3-5 months of age we find a type of intentional reaching that is called ballistic reaching. It is called ballistic because it seems as though the infant is throwing their hand at the target. It is not very accurate, and infants often miss their target. In addition, even when the hand does reach the target, it often fails to grasp the target for the reason mentioned above. Between 5-7 months of age infants improve their ability to coordinate their vision and control of their reaching. As a result, reaching becomes more deliberate and accurate. This type of reaching is called guided reaching. However, it is still somewhat imprecise, due in part to the persistent problem of coordinative their reach with their grasp. Finally, by about 11 months of age, infants succeed in coordinating their reach and grasp, with a corresponding increase in the accuracy of reaching and grasping. A curious tidbit here is that infants appear to use both hands equally for reaching and grasping until about nine months of age. However, between 9-13 months of age infants develop a preference for one hand over the other. By 13 months of age most infants tend to display a clear preference for their right hand.
Another major type of behavior that develops during infancy is walking. As adults we take walking for granted. However, it requires a lot more to learn how to walk than we might imagine. This is part of the reason why it has taken years to train robots to walk on two legs. Part of the reason it takes the average infant about 12 month to learn how to walk is that they must learn many other behaviors before they can walk. First, they have to learn how to reach. This is necessary in order for them to grab objects and either pull themselves to a standing position, or to maintain their balance at first. In addition, babies must first learn how to sit up. By about four months of age most babies can sit with support. They can sit and grasp by about five months, and they can sit without support by about seven months of age. By about eight months, most babies can crawl. They can also stand up if they have help. By the end of the eighth month most babies have developed the ability to pull themselves up to a standing position. However, it takes them another 2-3 months to learn how to stand alone. By about 12 months, most infants have learned how to walk alone. During the next few months infants refine their walking abilities by learning how to walk sideways and backwards (between 13-18 months). They expand these abilities still more by learning how to run between 14-20 months of age, though they may not be able to run smoothly until about two years of age. Further developments, such as turning while running will take a little longer, and occur during the childhood years.
Fine Motor Skills
Fine motor skills are the ability to use the small muscles of the body, especially the hands and fingers. Although these skills develop at the same time as gross motor skills, they tend to lag behind a bit, because the large muscles must be able to put the body in place for the small muscles to play their part.
As suggested above, the neonate is able to grasp objects, but only if they are placed in his/her hand, or if they accidently come into contact with the hand. At this point, most objects are held by the entire hand rather than just a couple, or few, fingers. Between 4-6 months of age infants become fairly successful at reaching for and grasping objects, though a few trials and errors may be common. An important milestone is reached at about nine months of age when infants develop the ability to hold small objects between the thumb and forefinger. This is called the pincer grasp. It is important because it eventually makes many other behaviors possible, such as writing or buttoning clothing. Between 10-12 months of age infants typically are able to hold a spoon in their hands and feed themselves, though their aim may still be rather poor.
As the baby learns how to control it's eyes and head, and other muscles, it soon finds that it cannot always acheive its goals without coordinating different parts of the body at the same time. As adults, we automatically move our body into position to enable our hands to pick up objects. Infants have to learn all of these things for themselves, largely through trial and error. Part of the reason it takes infants so long to learn how to do things that we now take for granted is that there really is an awful lot to learn. Just to give you an idea of what I mean, let me invite you to think about what is involved in something as seemingly simple as catching a ball. First, one must know that the ball is an animate object, that has substance and a consistent form (that is, it won't change shape in flight). In addition, one must be able to predict the trajectory of flight. One must be able to follow that trajectory with one's eyes. This, in turn, requires control of one's eyes, head, neck, and to some extent (depending on the trajectory of the ball), one's body. Then one must be able to predict where the ball will land, or perhaps where the ball's trajectory will come closest to one's own body. Having achieved these things, then one must prepare to catch the ball. This requires the ability to move one's entire body to a location where it will be close enough to the ball's trajectory for us to catch the ball. This also requires coordinating our body position with visual cues coming from our eyes. And it requires that we account for gravity by making adjustments in our legs and body, so that we don't lose balance and fall. Once our body is in place we must move our arms and hands into position. And our hands must be suffiently open to grasp the ball as it comes close enough to our body. If the hand is too open or closed then the ball may just bounce off. And once the ball comes into contact with our hand (or hands) then we must close our fingers quickly enough not to let the ball escape. Oh, and there is one more thing. We must do all of this in about 1-2 seconds. And, let's not forget that the infant brain is still immature, and so cannot process information as quickly as a child or adult.
Esther Thelen has observed that the predictable trajectory of the development of infant motor skills is due in large part to the fact that infants must solve certain types of problems before they can solve other types of problems. For instance, infants must learn how to control their eyes and head before they can intentionally grasp objects, or catch a ball. From this point of view, the development of the infant is a function of their innate physical characteristics and the relatively constant state of the physical world they inhabit, e.g., in terms of the laws of physics. In addition, the infant must learn how to control each subsystem (e.g., the eyes) before it can coordinate the activities of several subsytems (e.g., the eyes, legs, arms, and hands) to accomplish goals (e.g., catch a ball).
How Can I Nurture My Infant's Motor Development?
The development of a child's abilities depends on the interaction between the child and their environment. It is practice in their use that enables infants to develop these skills. Quite simply, if they don't practice they won't learn. So, part of the way to help nurture your child's motor development is to provide them with lots of opportunities to practice their motor skills. An easier way to put this is to just say, let them get lots of exercise. In addition, it helps if they have different types of objects to interact with. Expose them to different shapes, colors, and textures. Enable them to play with objects of different sizes and weights. Psychologists call these different opportunities that exist in the environment to play and develop their skills "affordances". And, above all, play with your children. I will discuss play in much more detail elsewhere. You may click here if you wish to go there now.