© 2019 GWEN DEWAR, PH.D., ALL RIGHTS RESERVED
Motor milestones mark exciting transitions in a baby’s life, but there is no single, universal schedule that all babies follow.
For example, by 6 weeks, most babies can lift up their heads while they lie on their stomachs.
By 3 months, most babies can also lift up their chests, using their arms for support.
By 4 to 5 months, the average baby can roll over, from back to stomach (Nelson et al 2004).
But the exact timing varies. Some babies have learned to roll over by two months! And the same is true for other motor milestones.
For instance, studies suggest that more than 50% of infants can
- sit up, unsupported, by 6 months,
- crawl on hands and knees by 8 and a half months,
- stand, unassisted, by 10 and a half months, and
- walk, unassisted, by 12 months.
Yet many babies reach these milestones months earlier – or months later.
To know if your baby is on track, you need to know about the range of what’s normal.
What's the earliest you might expect your baby to walk?
If your baby is slow, when should you be concerned about the possibility of a developmental delay?
And can parents do to support healthy development?
As we'll see, a baby's environment -- and personal quirks -- affect the timing of motor milestones. Babies develop skills faster when we encourage them to practice opportunities to practice.
Here is an overview of baby motor milestones, including the development of gross motor skills and fine motor skills. Throughout, I note ways in which parents can influence development, and end with some evidence-based tips.
Gross motor milestones
Gross motor skills involve the large muscles of the legs, trunk, and arms. And when it comes to babies, pediatricians and developmental scientists are especially focused on six of these skills:
- sitting up without support
- crawling
- standing with assistance
- walking with assistance
- standing without support
- walking without support
When can you expect your baby to achieve these motor milestones?
Every baby is different.
Some infants can sit up, unaided, by the age of 4 months. More than half of all babies have figured this out by 6 months. And about 10% of infants don’t achieve this particular milestone until they are 7.5 months or older.
Other motor milestones present an even wider range of timing. For instance, while the median age for learning to walk (unaided) is about 12 months, a few babies hit this milestone before the age of 9 months, and approximately 10% of babies don’t begin walking without support until they are more than 14.5 months old.
So if someone ever tries to sell you a chart of baby development “month by month," run the other way. That’s simply not how it works.
A better way to visualize the development of motor skills is to think in terms of developmental windows – time periods during which approximately 98% of babies can be expected to achieve a given milestone. Here’s an infographic I made to illustrate - -adapted from a figure published by the World Health Organization (WHO 2006b).
As you can see, some gross motor milestones tend to occur earlier than others, but the windows are wide, and they overlap each other. The resulting picture doesn’t predict when your baby will hit any particular milestone – not in any fine-grained sense. But it provides us with a realistic time range.
If a baby's development seems slow, when should you be concerned?
First, trust your intuitions. If, for any reason, you realize that you are concerned – whether or not you think you “should" be – talk to your pediatrician. If it turns out that your baby is having problems, early intervention can make a big difference.
Second, if you’re wondering about cutoff dates for achieving a given milestone, keep in mind: It depends. It depends on what other signs your baby is showing, and whether your baby has any known risk factors for a developmental problem.
But in the absence of any other concerns, a good rule of thumb is to pay attention to the 90th percentile – the age by which 90% of babies have achieved a given milestone (Sice 2007).
If your baby hasn’t reached a milestone by this date, consult with your pediatrician. Being slower doesn’t mean that your child has a developmental delay. But it’s a sign that your baby’s progress should be reviewed and monitored.
The previous chart doesn’t provide information about percentiles, so I’m going to add it here:
What about the order of motor milestones? Is there something wrong if a baby seems to skip a step, or experiences a reversal?
Not necessarily. Babies don’t always hit these milestones in the same order, and one of the milestones – crawling – isn’t even universal.
If you look at our graphics, you might reasonably assume that your baby will hit gross motor milestones in the following sequence:
(1) sitting up without support; (2) crawling on hands and knees; (3) standing with assistance; (4) walking with assistance; (5) standing without support; and (6) walking without support.
And indeed, when the World Health Organization (WHO) tracked the development of babies in 5 countries (Ghana, India, Norway, Oman and the USA), this pattern was found in the largest percentage of infants – about 42% of them.
But more than a third of the babies achieved milestone #3 (standing with assistance) before they crawled. Almost 9% of the babies also hit milestone #4 (walking with assistance) before crawling.
Another 10% of babies mixed the order up in even more exotic ways, and approximately 4% of babies never crawled on their hands and knees (WHO 2006a).
Other studies have reported even higher rates of babies who never crawled -- babies who were healthy and went on to walk within the normal time window.
So there isn’t a master sequence of motor development milestones that all babies follow. As motor development experts Karen Adolph and John Franchak (2016) explain:
“The milestone charts suggest an orderly, age-related march through a series of stages, but developmental pathways can differ and individual infants do not strictly adhere to the normative sequence derived from average onset ages. Infants can acquire skills in various orders, skip stages, and revert to earlier forms."
Why is there so much variation?
Some of it is cultural.
For example, in some African countries, parents actively train their babies to sit, stand, and walk. They provide infants with lots of practice, and this appears to accelerate the development of upright posture (Super 1976; Bril and Sabatier 1986; Karasik et al 2015; Adolph and Robinson 2015).
The notion is supported by experimental work.
Newborn babies have a "stepping reflex": If you hold a baby so that soles of his feet brush against the ground, the baby will spontaneously take steps -- long before the baby is capable of standing under his own weight.
The reflex usually disappears over time, but not if babies are given daily opportunities to practice the action, and such babies have reached the milestone of walking (without assistance) at an earlier age (Zelazo 1983).
So we've got evidence that parenting practices can speed up the pace of motor development. And the converse is also true: Parenting can slow it down.
In places where parents adopt a hands-off approach – or actively prevent babies from moving around during the day – infants take longer to achieve certain motor milestones (WHO 2006b; Mei 1994; Adolph and Robinson 2015; Adolf et al 2018).
What about crawling? Environmental factors play a big role there, too.
In places like the United States, parents expect babies to crawl, and they provide them with opportunities to do so. But this isn’t true everywhere, and it probably wasn’t true for our hunter-gatherer ancestors.
Crawling outdoors – in a world inhabited by predators – wouldn’t have been a good idea, and indeed, contemporary hunter-gatherers don’t encourage their infants to crawl.
As I explain in this guide to the development of crawling, it’s not unusual for babies to reject hands-and-knees crawling in favor of other methods of getting around – like scooting around on their bottoms, or rolling from place to place.
And it's clear that motor milestones are influenced by genetics.
When researchers have controlled for the effects of culture and parenting, they've found that genetic factors have an important impact on the timing of motor milestones (Smith et al 2017).
Siblings don't reach motor milestones at exactly the same time, even if they are raised under similar conditions. Individual differences in temperament, body fat composition, and other characteristics -- characteristics influenced by genes -- can affect a baby's activity patterns, leading some babies to spend more time practicing developing motor skills.
What about other motor milestones?
Holding objects
Two-month-old babies can hold onto small objects – if we place these objects directly into their hands. And they are likely to bring the items up to their mouths to investigate (Rochat 1989).
But the grasp of a young infant isn’t very secure or reliable. When babies arms flail around, they are likely to lose their grip on whatever they are holding.
Learning to reach for – and firmly grasp – objects
Between the ages of 4 and 6 months, most babies will have developed the manual dexterity to hold onto and shake a toy. They are also developing the ability to move an objects back and forth between hands.
Babies can successfully reach for a stationary object, but their movements are jerky, and babies aren’t yet good at catching a moving object. Babies don’t yet understand how to grasp large objects efficiently – they don’t show a preference for doing it with both hands.
Between 6 and 9 months, these skills improve considerably. Babies become proficient at catching hold of moving objects. For instance, they can grab rolling balls, and judge when some balls are rolling too fast to catch (van Hof et al 2008). By 11 months, babies also show better planning for picking up large objects – they consistently reach with both hands at once (Fagard and Jacquet 1996).
Fine motor control and tool use
By 8 to 10 months, most babies can show off fine motor skills. They are developing the ability to grasp small objects between the thumb and index finger. Babies are usually able to drink from a cup, and they are figuring out how to eat with a spoon.
But their attempts are awkward. If you provide them with a loaded spoon, they are likely to pick it up by the bowl end – not the handle (McCarty et al 2001; van Roon et al 2003). Moreover, they will hold onto the spoon with a fist grip, not a precision (thumb-to-index figure) grip.
By 14 months babies are more adept. They might still hold the spoon in a fist grip, but they’ve learned how to hold it by the handle (van Roon et al 2003).
And around this time – from 12 months onward – babies can use writing implements to draw random-looking marks and dots.
By 18 months, these efforts may become more controlled and organized, and may include straight lines and zig-zags (Dunst and Gorman 2009). More complex drawings – of geometric shapes, and figures with identifiable features (like a blob creature with legs) – develop slowly, and may not appear until a child is three years old (Dunst and Gorman 2009).
What can parents do to promote motor development?
Give your baby lots of "tummy time."
As I note in this article, it’s clear that “tummy time" is important. Babies develop better muscle control when they spend supervised time on their stomachs. It’s good for building neck strength, and it helps babies develop the ability to roll, crawl, and sit up from a lying position (Kuo et al 2008).
Help babies practice an upright posture.
We’ve also seen how parents can support the development of sitting and standing. Practice sessions – where you help your baby adopt an upright posture by providing support with your hands – may speed up development.
Help babies reach and grasp.
Not surprisingly, babies learn faster when we provide them with opportunities to touch, hold, and reach for objects.
For example, in experiments using mittens and toys covered in Velcro®, babies as young as 3 months have gotten extra practice handling objects that would ordinarily be hard to grasp. When parents encourage their babies to explore objects with such “sticky mittens," babies have shown long-term developmental benefits (Needham et al 2017; Libertus et al 2015).
Let babies bang.
It’s noisy and obnoxious, but researchers think that babies develop important motor skills when they grab onto an object and bang away (Kahrs et al 2012). Just make sure the object is safe for your baby to use!
Encourage free play – and make yourself a visible, responsive, and non-bossy playmate.
Babies exercise more – and spend more time interacting with objects – when we provide them with the time and space to engage in free play (Adolf and Koch 2019). And babies benefit when we get down on the floor to interact with them.
More reading
For more information about baby development, see this index to Parenting Science articles.
References: Motor milestones
Adolph K. 2008. Motor and physical development: Locomotion. In M.M. Haith and J.B. Benson (Eds), Encyclopedia of infant and early childhood development, M.M. Haith and J.B. Benson (Eds), San Diego: Academic Press, pp. 359-373.
Adolph KE and Robinson SR 2015. Motor development. In R. M. Lerner (Series Eds.) and L. Liben and U. Muller (Eds), Handbook of child psychology and developmental science: Vol. 2: Cognitive processes (7th ed.) New York: Wiley, pp. 114-157
Adolph KE and Hoch JE 2019. Motor development: Embodied, embedded, enculturated, and enabling. Annual Review of Psychology, 70, 141-164.
Adolph KE, Hoch JE, Cole WG. 2018. Development (of Walking): 15 Suggestions. Trends Cogn Sci. 22(8):699-711.
Bril B, Sabatier C. The cultural context of motor development: Postural manipulations in the daily life of Bambara babies (Mali) International Journal of Behavioral Development. 1986;9:439–453.
Dunst C., Gorman E. (2009). Development of infant and toddler mark making and scribbling. Cent. Early Learn. Lit. Rev. 2, 1–16.
Fagard J, Jacquet AY. Changes in reaching and grasping objects of different sizes between 7 and 13 months of age. British Journal of Developmental Psychology. 1996;14:65–78.
Kahrs BA, Jung WP, Lockman JJ. 2012. What is the role of infant banging in the development of tool use? Exp Brain Res. 218(2):315-20.
Kuo YL, Liao HF, Chen PC, Hsieh WS, Hwang AW. 2008. The influence of wakeful prone positioning on motor development during the early life. J Dev Behav Pediatr. 29(5):367-76.
Libertus K, Joh AS, Needham AW. 2016. Motor training at 3 months affects object exploration 12 months later. Dev Sci. 19(6):1058-1066.
McCarty ME, Clifton RK, and Collard RR. 2001. The beginnings of tool use by infants and toddlers. Infancy 2: 233-56.
Mei, J. 1994. The Northern Chinese custom of rearing babies in sandbags: implications for motor and intellectual development. In: vanRossum, J.; Laszlo, J., editors. Motor development: Aspects of normal and delayed development. Amsterdam: VU Uitgeverij.
Needham AW, Wiesen SE, Hejazi JN, Libertus K, Christopher C. 2017. Characteristics of brief sticky mittens training that lead to increases in object exploration. J Exp Child Psychol. 164:209-224
Nelson EA1, Yu LM, Wong D, Wong HY, Yim L. 2004. Rolling over in infants: age, ethnicity, and cultural differences. Dev Med Child Neurol. 46(10):706-9.
Rochat R 1989 Object Manipulation and Exploration in 2- to 5-Month-Old Infants Developmental Psychology 25 (6): 871-884
Sices L. 2007. Use of developmental milestones in pediatric residency training and practice: time to rethink the meaning of the mean. J Dev Behav Pediatr. 28(1):47-52.
Smith L, van Jaarsveld CHM, Llewellyn CH, Fildes A, López Sánchez GF, Wardle J, Fisher A. 2017. Genetic and Environmental Influences on Developmental Milestones and Movement: Results From the Gemini Cohort Study. Res Q Exerc Sport. 88(4):401-407.
Super CM. 1976. Environmental effects on motor development: the case of "African infant precocity". Dev Med Child Neurol. 18(5):561-7.
vam Hof P, Kamp J, Savelsbergh GJP. 2002. The relation of unimanual and bimanual reaching to crossing the midline. Child Dev. 73:1353–1362.
van Roon D, van der Kamp J, Steenbergen B 2003. Constraints in children’s learning to use spoons. In: Savelsbergh G, Davids K, van der Kamp J, Bennett SJ, eds. Development of Movement Co-ordination in Children: Applications in the Fields of Ergonomics, Health Sciences and Sport. Routledge, London: 75-93.
WHO Multicentre Growth Reference Study Group. 2006a. Assessment of sex differences and heterogeneity in motor milestone attainment among populations in the WHO Multicentre Growth Reference Study. Acta Paediatr Suppl. 450:66-75.
WHO Multicentre Growth Reference Study Group. 2006b. WHO Motor Development Study: windows of achievement for six gross motor development milestones. Acta Paediatr Suppl. 450:86-95.
Zelazo PR 1983. The development of walking: New findings and old solutions. Journal of Motor Behavior 15: 99-137.
Image credits for "Motor milestones"
title image of baby doing the plank by Doug LeMoine / flickr
image of mother helping baby walk by K Harsha / flickr
image of baby holding plastic eggs by mliu / flickr
image of baby drawing with chalk by Quinn Dombrowski / flickr
charts (adapted from WHO 2006) copyright Parenting Science
Source: https://www.parentingscience.com/motor-milestones.html
The content is owned by . Visit site here for other valuable articles.
No comments:
Post a Comment