Development in Infancy (VCE SSCE Health and Human Development): Revision Notes
Development in Infancy
Infancy marks the first major stage of life after birth, spanning from birth to the second birthday. During this critical period, babies transform from relatively helpless newborns into toddlers who can walk, talk, and interact meaningfully with their world. This stage is characterised by rapid development across all domains: physical, social, emotional, and intellectual.
What infants need for healthy development
Newborn babies are entirely dependent on others for survival. They cannot feed themselves, maintain body warmth, or stay clean and hydrated without assistance. To develop properly, infants require:
- A primary caregiver with whom they can form a secure attachment
- Adults who can understand and respond to their signals and needs
- Sensory stimulation through things to look at, touch, hear, smell, and taste
- Opportunities to play and explore their environment
- Appropriate language stimulation and interaction
- Support in acquiring new motor, language, and thinking skills
- Chances to develop some independence
- Guidance in learning to control their own behaviour
Development during infancy is influenced by multiple factors, including genetic potential, nutrition, health status, parenting style, socioeconomic status, and the physical and prenatal environment. Each infant develops at their own pace while following general developmental patterns.
The combination of genetic factors and environmental influences means that while all infants follow similar developmental patterns, the timing and rate of development can vary significantly from child to child. This variation is completely normal and expected.
Understanding developmental milestones
A developmental milestone refers to a significant skill or event that typically occurs at a particular age in a person's life. Examples include learning to walk, saying a first word, or getting a job. For infants, these milestones are usually expressed as age ranges rather than exact ages, because children develop at different rates.
The ages given for developmental milestones represent averages. Some children will achieve certain skills earlier, whilst others may take a bit longer. Both situations can be completely normal. However, tracking milestones helps parents and health professionals identify any potential developmental concerns early.
Physical development milestones
| Age | Key milestones |
|---|---|
| 2 months | - Holds head up - Begins to push up when lying on stomach |
| 6 months | - Rolls over front to back, back to front - Begins to sit without support - Supports weight on legs when standing |
| 9 months | - Can stand if holding onto things - Sits without support - Pulls to standing - Crawls |
| 12 months | - Gets to a sitting position without help - Pulls up to stand - Walks holding on to furniture (known as 'cruising') - May take a few steps without holding on - May be able to stand alone |
| 18 months | - Can walk alone - Can walk and pull a toy along - Drinks from a cup - Eats with a spoon |
| 2 years | - Kicks a ball - Begins to run - Climbs on and off furniture without help - Walks up and down stairs holding on - Throws ball overhand |
Using percentile charts
Percentile charts are valuable tools used by health professionals to track a child's physical development. These charts compare a child's growth, weight, and head circumference measurements with those of other children in the same age group.
Understanding percentiles is straightforward. A baby on the 50th percentile for weight is right in the middle of the normal range: 50% of babies their age are lighter, and 50% are heavier. A baby on the 5th percentile weighs less than 95% of other babies of that age, whilst a baby on the 90th percentile weighs more than 90% of other babies that age.
The key point is not which percentile a baby is on, but whether they are growing consistently along their own percentile line. Some babies will naturally be smaller, and others larger, and both can be perfectly healthy.
Separate charts are used for boys and girls because their growth rates and patterns differ. Infant growth from birth to two years is typically measured using the World Health Organization's growth standards, which provide reliable benchmarks for healthy development.
Physical development
Growth patterns
Infancy is the second fastest period of physical growth in the entire lifespan, surpassed only by the prenatal stage. The rate of physical change during these first two years is remarkable:
Weight changes:
- Birthweight doubles by six months
- Birthweight triples by twelve months
- Body fat increases during the first year (known as 'baby fat'), which helps maintain body temperature
- As the baby grows and builds muscle, this baby fat gradually disappears
Body proportions:
- At birth, an infant's head represents about 1/3 of their entire body
- By age 2, the head is about 1/4 of total body length
- By adulthood, the head represents only about 1/8 of body length
- This change reflects the cephalocaudal pattern of development
Worked Example: Understanding Body Proportion Changes
At birth:
- Head = of body length
At age 2:
- Head = of body length
At adulthood:
- Head = of body length
This demonstrates the cephalocaudal (head-to-toe) growth pattern, where the head starts proportionally larger and the rest of the body catches up over time.
Brain development:
- At birth, the neonate's brain is 33% of its adult size but only 25% of its adult weight
- By the end of the second year, the brain weighs about 75% of an adult brain
- By puberty, it weighs nearly 100% of an adult brain
Muscle and bone development:
- Muscles account for about 25% of weight at birth
- No new muscles develop after birth, but existing muscles increase in thickness and length
- During the first 18 months, muscle mass increases at twice the rate of bones
- Bones continue to ossify (harden), increasing in size and weight
- This hardening enables the child to support their own weight, stand, and walk by around age one
Sleep is crucial for the developing infant. During sleep, a baby's brain cells establish important connections and pathways that enable learning, movement, and thought. These neural pathways are essential for understanding everything they experience through their senses.
Changes to body systems
Nervous system: The network of nerves that transmits messages to and from the brain and between brain cells becomes increasingly complex during infancy. A fatty substance called myelin develops around nerve fibres, allowing messages to be transmitted more rapidly and efficiently. This process of myelination is essential for coordinated movement and faster responses.
Sensory development: All five senses function from birth, though they continue to develop and become more acute over time. Although vision is initially quite blurry, infants soon begin to recognise familiar faces and sounds. The developing senses allow babies to understand and interact with their world.
Dental development: At birth, a baby already has a full set of 20 primary teeth (also called baby teeth, milk teeth, or deciduous teeth) hidden within the gums. These consist of 10 teeth in the upper jaw and 10 in the lower jaw. The process of teeth breaking through the gumline is called eruption or, in babies, teething.
The timing of tooth eruption varies considerably between children. Generally, a baby's first tooth appears between 6 to 9 months of age, though it can occur as early as a few months old or as late as 12 months or more. By 3 years of age, most children have a complete set of 20 primary teeth.
Skeletal development: Newborn babies have approximately 300 bones, many of which are made entirely or partly of flexible cartilage. This flexibility helps protect babies from breaks as they learn to crawl, walk, and run. As the body matures, many of these bones fuse together, resulting in the 206 bones found in adults. Interestingly, the leg bones (femur and tibia) of a 3-year-old child are already half their eventual adult length.
Motor skill development
Motor skills refer to the ability to control body movements. Development follows two important patterns:
Cephalocaudal development means that development occurs from the head downwards. Infants gain control over their head and neck before their torso, and control their torso before their legs. This is why babies can hold their heads up before they can sit, and sit before they can stand.
Proximodistal development means that development occurs from the core or centre of the body outwards towards the extremities. Infants develop control of their shoulders and torso before gaining fine control of their hands and fingers.
Worked Example: Motor Development Patterns
Cephalocaudal sequence:
- Head control (2 months)
- Sitting with support (4-6 months)
- Sitting alone (6-8 months)
- Standing (9-12 months)
- Walking (12-15 months)
Proximodistal sequence:
- Shoulder control (reaching)
- Arm control (grasping)
- Hand control (holding objects)
- Finger control (pincer grasp at 9-12 months)
From reflexes to controlled movements: Reflexes are automatic reactions to stimulation that enable infants to respond to their environment before any learning has occurred. For example, babies automatically suck when presented with a nipple, grasp at a finger pressed into their hand, and startle when exposed to loud noises. As motor skills develop, these reflexes are gradually replaced by controlled, purposeful movements.
Developing motor control: A newborn has limited control over their body, but they quickly learn new skills. They soon master lifting their head and rolling over. Around six months, most infants begin crawling. As proximodistal development continues, an infant learns to reach for toys using shoulder and torso rotation. They develop a pincer grasp, using thumb and forefinger to pick up small objects. They become able to place objects into containers and take them out, and begin functional activities like holding a spoon or turning pages in a book.
By the age of one, most infants can support their own weight, and many can stand and walk. By age two, they can usually throw and kick a large ball. The development of these motor skills opens up new opportunities for exploration, play, and learning.
Social development
Social development during infancy centres primarily on relationships with family members and close caregivers. The infant is completely dependent on adults and learns social skills by observing and interacting with these important people in their life.
Relationships and family influence
The family is the most significant influence on social development during infancy. Parents and other primary caregivers are the infant's first teachers of social behaviour. Through daily interactions, infants learn how to communicate, how to behave in social situations, and what responses to expect from others. The quality of these early relationships forms the foundation for later social development.
Communication skills
Social communication begins very early in infancy:
- At around six weeks, infants begin to smile, often in response to faces or voices
- After approximately six months, they start to recognise and interpret the facial expressions of others, such as distinguishing between a smile and a frown
- They learn to use simple gestures like shaking their head for 'no' or waving for 'bye-bye'
- As language develops, infants can express their needs and wants more clearly, facilitating social interaction
Developing social behaviours
As infants develop and their motor skills improve, play becomes an important part of social development. They enjoy games and become increasingly responsive to interaction.
Separation and stranger anxiety: Separation anxiety typically begins around eight months old, as babies start to become aware of themselves as separate individuals and recognise who other people are. An infant may hide their face or react strongly when a parent leaves for work. This anxiety usually peaks between 9 and 18 months and generally fades before the second birthday.
Around one year of age, it's normal for some children to appear shy or nervous around strangers. This stranger anxiety is a natural part of development and shows that the infant can distinguish between familiar and unfamiliar people.
Both separation anxiety and stranger anxiety are positive signs of healthy development. They indicate that the infant has formed strong attachments to caregivers and can differentiate between familiar and unfamiliar people.
Play and interaction with peers: Infants enjoy being around and observing other children, but they are unlikely to play cooperatively with them during infancy. They may cry if someone touches their favourite toy and might snatch toys from others. This behaviour is normal because infants haven't yet developed empathy for others' feelings or learned about sharing.
An 18-month-old may be able to say "thank you" but not necessarily grasp the true meaning of the word. By two and a half years, children begin to link words to concepts and can display basic manners with understanding.
Imitation and learning: Infants learn a great deal through observation and imitation. They start to mimic behaviours such as waving, talking on the phone, or pretending to have a meal. These imitative behaviours show that the infant is learning about social roles and everyday activities.
By the age of three, many children are beginning to understand concepts like turn-taking and sharing, though these skills are still developing. The social behaviours learned during infancy form the foundation for more complex social interactions in later childhood.
Emotional development
Emotional development during infancy revolves around relationships with family members and primary caregivers. These early emotional experiences shape how infants understand and express their feelings.
Experiencing a range of emotions
One of the first signs of emotional development is when a hurt or distressed infant can be comforted by their caregivers. This shows that the infant is beginning to associate their caregivers with safety and comfort.
Emotional attachment: Within the first few months of life, emotional attachment forms between infants and their caregivers. This attachment is crucial because it helps the infant feel secure, safe, and loved. It also builds trust, which is fundamental to healthy emotional development. The emotional bond between caregivers and infant can be so strong that the infant may become distressed when held by a stranger or when a caregiver leaves the room.
The role of breastfeeding: Breastfeeding promotes social and emotional attachment between mother and child. The secretion of maternal hormones prolactin and oxytocin encourages the development of a maternal bond. Oxytocin plays a role in counteracting stress, helping both mother and baby feel comfortable and relaxed during feeding times.
While breastfeeding promotes attachment through hormonal mechanisms, secure attachment can also develop through other forms of feeding and caregiving. The key factor is responsive, consistent care that meets the infant's physical and emotional needs.
Separation anxiety: This form of anxiety typically peaks between 9 and 18 months and usually fades before the second birthday. During this period, infants may become visibly upset when separated from their primary caregivers, showing the strength of their emotional attachment.
Stranger anxiety: Stranger anxiety is a reaction of distress when an infant encounters an unfamiliar person. This is a normal part of development and demonstrates that the infant can distinguish between familiar and unfamiliar people. Fear may also be shown when confronted by unfamiliar things such as a clown or a dog.
Learning appropriate ways of expressing emotion
As infants grow, they develop the ability to express a wider range of emotions in increasingly sophisticated ways:
- By eight months, infants can clearly express anger and happiness
- They may become frustrated if interrupted during activities (such as when playing games)
- This frustration may result in tantrum-throwing in later months
- By 12 months, infants become sensitive to approval from parents or carers and may become upset or distressed if approval is not given
Social interactions offer opportunities to practise impulse control and make progress in learning about cooperative play and sharing. Infants experience, express, and perceive emotions before they fully understand them. Developing the capacity to control their impulses helps an infant adapt to social situations, follow rules, and become increasingly able to exercise control over their behaviour.
Developing self-concept
Self-concept refers to how we see and understand ourselves as individuals.
Early infancy (birth to 9 months): Babies do not initially understand that they exist as separate people from their caregivers. They experience the world but don't yet recognise themselves as distinct individuals.
Around 9 months: At this stage, babies begin to experience separation anxiety, which indicates they're starting to understand that they exist separately from their caregivers. This is an important milestone in developing self-awareness.
Worked Example: Self-Concept Development Timeline
Birth to 9 months:
- No sense of being separate from caregivers
- Experiences world without self-awareness
9 months:
- Separation anxiety begins → signals emerging self-awareness
- Starting to recognise self as distinct individual
1-2 years (toddler stage):
- Growing self-awareness
- Self-concept based on concrete abilities: "I can walk", "I can hold a spoon"
- Self-confidence grows as capabilities increase
Approaching 3 years:
- Understands their mind is separate from others' minds
- Recognises their thoughts/feelings may differ from others
- Sees self as "able to do things"
Toddler stage (1-2 years): Toddlers become more self-aware, and relationships with caregivers continue to play a vital role in developing a sense of self. Toddlers can sense how others feel about them, which significantly influences how they feel about themselves. As they become more capable and more aware of themselves as individuals, their self-confidence in their own abilities grows. Their sense of self is concrete and based largely on what they can see and do, such as "I can walk" or "I can hold a spoon."
Preschool years (approaching 3 years): Preschoolers become more independent and see themselves as 'able to do things'. They have learned that their minds are separate from others' minds, and that their thoughts and feelings may be different from those around them. This represents a significant advance in self-awareness and understanding.
Intellectual development
Intellectual development during infancy is rapid and remarkable. From the moment of birth, babies are capable of learning, and every new experience contributes to their cognitive development.
Knowledge and memory
Learning through the senses: From birth, all five senses are working, although they become more acute over time. Sight, smell, hearing, touch, and taste are how babies understand the world around them. Many infants collect information by putting objects into their mouths. This oral exploration is how they learn about concepts such as hard, soft, bitter, and sweet. As infants develop, they start to rely more on their other senses for learning.
Word-object associations: Within months, infants recognise their own name and respond when called. This word-object association progressively develops:
- Infants begin to recognise the names of favourite people, toys, and other objects
- They learn to identify basic colours
- They understand simple commands
- By the end of infancy, they can associate hundreds of words with their meanings
Understanding cause and effect: Early infancy signifies an emerging understanding of cause and effect. Infants begin to associate certain actions with particular outcomes:
- If they cry, they get attention
- If they reach for someone, that person may pick them up
- If they kick their legs around, their caregivers might play with them
- If they drop a toy, it falls to the ground
This understanding of cause and effect is fundamental to problem-solving and further learning.
The importance of exposure: For a child to learn about people, places, and things, they need to be exposed to them. Every new interaction gives them information about the world and their place in it. This is why providing infants with varied experiences and environments is so important for their intellectual development.
Language development
Language develops rapidly during infancy, allowing infants to interact more effectively with those around them:
Early language (0-3 months):
- Makes speech-like sounds such as 'goo' and 'gaa'
- Cries to communicate needs
- Responds to voices and sounds
First words (around 12 months):
- Can say a couple of basic words like 'dada' or 'mumma'
- Understands more words than they can say
- Uses gestures to communicate
Rapid expansion (18-24 months):
- Language development occurs very quickly after the first birthday
- By the end of infancy, individuals can say around 150-300 words
- There is still confusion in context and pronunciation, but comprehension is growing rapidly
Supporting language development: Reading aloud is important for building a child's vocabulary and boosting their imagination and language skills. When parents and caregivers talk and interact with children, it helps them develop the ability to think and express themselves. Children learn language quickly through:
- Hearing and singing songs
- Having stories told or read to them
- Repeating rhymes
- Playing games
- Daily conversation and interaction
Attention span
The attention span of an infant is naturally very short:
- It may last only a matter of seconds for a single activity
- Certainly no longer than a minute for simple activities like playing with a toy
- Infants may give extra attention to games and objects they find particularly interesting, but still only for very short periods
- Any new activity or event will easily distract an infant
This short attention span is completely normal and reflects the infant's developing ability to focus and concentrate. As they grow, their attention span gradually lengthens.
Thought patterns and problem-solving
Peekaboo and cognitive development: At around six months of age, infants can enjoy basic games such as peekaboo. This game reflects important cognitive developments:
- The ability to compare themselves to others
- The ability to perceive differences and likenesses
- Memory development
- The display of new emotions like surprise and delight
Object permanence: At around six months of age, most infants have not yet grasped the concept of object permanence. Object permanence is the awareness that objects continue to exist even when they are out of sight.
Worked Example: Understanding Object Permanence
Before object permanence develops (0-6 months):
- Toy visible on table → infant sees and reaches for it
- Adult covers toy with cloth → from infant's perspective, toy has ceased to exist
- Infant does not search for toy under cloth
After object permanence develops (6-12 months):
- Toy visible on table → infant sees and reaches for it
- Adult covers toy with cloth → infant remembers toy still exists
- Infant lifts cloth to find toy
This explains why peekaboo is so delightful - when caregiver's face is hidden, younger infants genuinely believe they've disappeared!
In the mind of a young infant, an object that cannot be seen no longer exists. A toy placed in a cupboard, from the infant's perspective, has ceased to exist. This explains why infants get so much joy from playing peekaboo - when the caregiver's face is hidden, the infant genuinely believes they've disappeared!
As infants develop intellectually, they begin to understand that people and objects continue to exist even when they can't see them. They can create a mental image of the person or object, complete with memories of how they sound, feel, and smell. They can feel the security of the object or person's presence whilst maintaining a separateness that is now their emerging 'self'. This cognitive milestone typically develops between 6 and 12 months of age.
Developing problem-solving abilities: All infants need access to a variety of simple play materials suitable for their developmental stage. Importantly, these don't need to be expensive shop-bought toys. Water, sand, cardboard boxes, wooden building blocks, and pots and lids are just as valuable for facilitating learning as commercial toys.
Sometimes it's helpful to provide toys and activities that are slightly beyond an infant's current abilities. When an activity doesn't come easily, infants must work out a new way to accomplish it, which develops their problem-solving ability. This challenges them to think creatively and persist with tasks, building important cognitive skills.
Key Points to Remember:
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Infancy spans from birth to the second birthday and is marked by rapid development across all areas: physical, social, emotional, and intellectual.
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Developmental milestones occur at different ages for different children. Whilst average ages provide useful guidelines, there's a normal range of variation. The important thing is consistent progress over time.
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Physical development includes doubling birthweight by 6 months, tripling it by 12 months, and developing motor skills following cephalocaudal (head to toe) and proximodistal (core to extremities) patterns. Most infants can walk by their first birthday.
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Social development centres on family relationships. Infants learn by observing caregivers and develop communication skills including facial expressions, gestures, and early language. Separation anxiety typically peaks between 9-18 months.
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Emotional development involves forming secure attachments with caregivers, learning to express emotions appropriately, and developing self-concept. Infants don't recognise themselves as separate individuals until around 9 months old.
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Intellectual development includes rapid language acquisition (150-300 words by age 2), developing object permanence around 6 months, learning cause and effect, and building problem-solving skills through play and exploration. All learning occurs through the five senses and interaction with the environment.