3.2 Motor Development in Infants and Toddlers

Newborn Reflexes

Babies are born with several reflexes (Table 3.5). Some, like coughing, sneezing, and blinking, stay with us, while others, like rooting, disappear.

Why do newborns have reflexes? Some, such as the sucking reflex for nursing or bottle feeding, are for survival. Others are a stress response connected to the sympathetic nervous system. For example, the Moro reflex, also called the startle reflex, is activated when the infant is startled by a sudden movement or noise. The head automatically moves back, and the arms and legs flail out. Other reflexes do not have clear functions but are appealing to see, like the Babinski and plantar reflexes. If you glide your finger on the inner sole of the infant’s foot beneath their toes, the toes curl up, but if you stroke the outer sole, the toes spread out (Figure 3.12).

Figure 3.12 Newborn reflexes include (a) the Moro reflex, similar to a falling response; (b) the palmar reflex when infants grasp an object in their palm; (c) the rooting reflex; and (4) the tonic reflex. (credit a: modification of work “Moro reflex” by “Patty 2”/Wikimedia Commons, Public Domain; credit b: modification of work “Baby” by “NappyStock”/nappy, Public Domain; credit c: “Alden” by Diana Riser/Flickr, CC BY 4.0; credit d: modification of work “Asymmetrical tonic neck reflex (ATNR) at Two Months” by “Mjlissner”/Wikimedia Commons, CC0 1.0)

Some reflexes may be absent in newborns who have neurological impairments or who were born preterm, for example, while others may remain beyond the typical age of disappearance. Health-care professionals are likely to check for the appearance and disappearance of various reflexes to better understand how infants are developing and provide early intervention when needed (Swapna et al., 2020). This scan often begins with the Apgar test immediately after birth.

Milestones in Motor Development

Motor development milestones in the first two years of life are rapid and dramatic, and parents and caregivers often eagerly anticipate their child’s learning to sit, stand, and walk. Each achievement occurs during a given time span. The average age for walking is twelve months, for example, but infants can begin to walk as early as eight months or as late as seventeen to eighteen months. These milestones follow the predictable sequence of cephalocaudal and proximodistal development. For example, following the cephalocaudal pattern, infants are first able to hold their heads up, then sit, pull up, and finally walk. In the proximodistal pattern, infants can grab an object with their full hand before they can manipulate it with individual fingers.

Fine Motor Skills

Although gross motor skills typically appear first, infants and toddlers are also beginning to develop fine motor skills, coordinated movements performed by small muscles to manipulate and control objects or perform precise tasks like reaching for and grasping an object (Table 3.7). Finger movements readily come to mind, but the toes, eyes, face, tongue, and lips also execute fine motor movements.

Fine Motor Skill Milestone	Average Age Expected
Opens hands briefly	2 months
Holds a toy when put in their hand	4 months
Brings hand to mouth	4 months
Reaches to grab toy	6 months
Bangs objects together	9 months
Transfers objects between hands	9 months
Grasps with two fingers	12 months
Feeds self with fingers	18 months
Tries to use buttons or switches on a toy	24 months

Table 3.7 Average Age for Fine Motor Skills Emerging in the First Two Years of Life (source: CDC, 2024)

Like gross motor skills, fine motor skills often develop in a predictable sequence. At about four months of age, the infant uses two hands to reach for an object and then with more experience uses only one arm. Grasping begins with hands and palms (no thumb), a skill called the ulnar grasp. At about six months, the palmar grasp reflex is replaced by voluntary grasping. Infants begin to use their thumbs at around nine months of age when they grasp with their forefinger and thumb (Figure 3.13), dramatically improving the ability to control and manipulate objects. These coordinated actions are quite an accomplishment in only a few months’ time.

Figure 3.13 One indicator that an infant may be ready for solid food is the ability to pick it up with their fingers for self-feeding. This usually happens by twelve months. (credit: modification of work “20210805-FNS-UNC-0024” by U.S. Department of Agriculture/Flickr, Public domain)

The development of fine motor skills improves with practice, as you can observe if you watch an infant pick up objects and put them into a container repeatedly. With practice, infants will change their grasping patterns to fit the shape and size of the objects (Barrett et al., 2008). Fine motor skills, much like gross motor skills, also show variability based on family environment, culture, and opportunities to practice various movements (Hoch et al., 2024). For example, being in a home with more access to toys that call upon fine motor skills predicts improved fine motor skills.

Motor skills are also the result of interactions with other domains of development. For example, infants must plan and use their senses to move about in their environment. The ability to speak is also dependent on their being able to control the muscles in their mouth and larynx. In addition, although motor skills may appear to develop as individual skills, they build on each other, with each new one serving as the foundation for the next. As infants get older, individual motor skills combine into more complex skills, allowing infants to explore and learn about their surroundings.

Link to Learning

The development of fine motor skills during infancy allows infants to feed themselves and explore their environment. Many of these skills are learned through play.

Motor Development as a Dynamic System

One theory that has helped developmental psychologists understand the complexities of motor development is dynamic systems theory, which posits that developmental behaviors and milestones are the result of interactions between systems, including those within the individual. According to the original theorist, Esther Thelen, motor development is the result of interactions between internal developmental domains (e.g., cognition and the senses), maturation, and the environment (Fujihira & Taga, 2023; Thelen & Smith, 2007). For example, to walk, a child must have several coordinated and developed internal systems including balance, leg muscles, stepping movements, coordination, vision, and spatial awareness (Thelen & Ulrich, 1991).

From a dynamic systems perspective, every motor skill results from multiple maturational and environmental processes. For example, growth in the cerebellum, which contributes to balance and coordination, myelination of the nervous system, and synaptic pruning are critical for acquiring both fine and gross motor skills (Morizawa et al., 2022; Tiemeier et al., 2010). Gross motor skills are also influenced by genetics. Identical twins, who have nearly identical genetic makeup, are more similar in the timing of their motor milestones than fraternal twins, who share around half of the same genes (Ooki, 2006). However, even identical twins have unique experiences that can result in very different motor skill capabilities, as developmental psychologist and neurobiologist Myrtle McGraw observed in case study experiments in the 1930s (McGraw, 1935; Parnin, 2022).

Dynamic systems theory has since expanded into a dynamic systems approach, applying the theory to other domains of development over the lifespan, including cognition and language (Fogel, 2011; Spencer et al., 2011). You may notice that this approach incorporates many of the theories you learned about in Chapter 1 Lifespan Psychology and Developmental Theories, such as cognitive development and behavioral genetics.

Experience and Motor Development

While the dynamic systems approach improves our understanding of the influences of systems within the individual, ecological systems and sociocultural theories inform our view of the factors outside the individual that shape developmental outcomes. These can come from cultural and familial environments as well as from individual play behaviors and resources.

Although the sequence of motor milestones is expected to be similar for all children, the timing and abilities can vary widely, demonstrating that environmental and cultural factors play an important role (Adolph & Hoch, 2019). For example, in Tajikistan, infants are regularly swaddled and placed in gahvora cradles for long periods of time. Because of their temporary immobility, these infants reach motor milestones later (Karasik et al., 2018).

In Northern China, where infants lie on their backs with their body movement restricted by being buried in a bag of fine sand for most of the day for toileting practice, the onset of sitting, crawling, and walking is delayed by several months (Mei, 1994). In other cultures, such as in the United States, Argentina, South Korea, and Italy, infants spend a lot of time sitting with postural support from furniture (United States and Argentina) or their mother’s arms (South Korea and Italy) (Karasik et al., 2015). In contrast, infants in Western Kenya have more practice with both supported and independent sitting, which may allow them to sit independently somewhat earlier than in cultures where infants are provided with a lot of support while sitting (Karasik et al., 2015).

Crawling and walking also show great variability based on culture and parenting beliefs. In some cultures, infants skip crawling or walk before they crawl, based on factors like maternal handling, cultural beliefs, and whether parents encourage or discourage crawling (Adolph et al., 2018; Super, 1976). Parenting beliefs can also influence the way they handle their infants. In some cultures, caregivers perform exercises to encourage motor development that might be viewed as rough in another culture (Adolph et al., 2018).

In another example, research following the Back to Sleep campaign has shown that infants placed on their backs while sleeping reach some motor milestones significantly later than infants who slept on their stomachs (Brouwer et al., 2006; Johnson, 2004). In response, pediatricians began encouraging parents to give their infants “tummy time,” which is associated with earlier development of gross motor skills such as walking, standing, and sitting (Hewitt et al., 2020).

Play

Play uses motor skills and cognitive skills, both connected to brain development. For example, with time and practice, the infant who begins by grasping a spoon is soon able to use it as a tool for eating. Besides the physical ability required to do this, the child also uses cognitive skills to play. Using paintbrushes, crayons, balls, and blocks in play takes similar planning and coordination. By one year, the child can point to objects of interest, use more motor skills to explore environments, and interact more with others during playtime. At eighteen months, the child may seek interaction, enjoy patty-cake, and clap during play. Parents and caregivers can support motor development through play by providing age-appropriate toys and activities and encouraging exploration and movement in a safe, supportive environment (Table 3.8).

Play starts in infancy and can inform several aspects of early development including motor skills, social interaction, self-exploration, and exploration of the environment. Play also helps caregivers and health-care providers observe how well development is progressing.