Normal child development, hearing and vision
Normal development in the first few years of life is monitored:
• by parents, who are provided with guidance about normal development in their child’s personal child health record and in a book Birth to Five, given to all parents in the UK
• at regular child health surveillance checks
• whenever a young child is seen by a healthcare professional, when a brief opportunistic overview is made.
The main objective of assessing a young child’s development is the early detection of delayed or abnormal development in order to:
• help children achieve their maximum potential
• provide treatment or therapy promptly (particularly important for impairment of hearing and vision)
• act as an entry point for the care and management of the child with special needs.
This chapter covers normal development. Delayed or abnormal development and the child with special needs are considered in Chapter 4.
Influence of heredity and environment
A child’s development represents the interaction of heredity and the environment on the developing brain. Heredity determines the potential of the child, while the environment influences the extent to which that potential is achieved. For optimal development, the environment has to meet the child’s physical and psychological needs (Fig. 3.1). These vary with age and stage of development:

• Infants are totally physically dependent on their parents and require a limited number of carers to meet their psychological needs.
• Primary school-age children can meet some of their physical needs and cope with many social relationships.
• Adolescents are able to meet most of their physical needs while experiencing increasingly complex emotional needs.
Fields of development
There are four fields of developmental skills to consider whenever a young child is seen (Fig. 3.2):
Gross motor skills are the most obvious initial area of developmental progress. As fine motor skills require good vision, these are grouped together; similarly, normal speech and language development depends on reasonable hearing and so these are also considered together. Social, emotional and behavioural skills are a spectrum of psychological development.
The acquisition of developmental abilities for each skill field follows a remarkably constant pattern between children, but may vary in rate. It is like a sequential story. Thus, the normal pattern for acquisition of skills:
• should always be considered longitudinally, relating each stage to what has gone before and what lies ahead
A deficiency in any one skill area can have an impact on other areas. For instance, a hearing impairment may affect a child’s language, social and communication skills and behaviour. As a child grows, additional skills become important, such as attention and concentration and how an individual child manages to integrate their skills.
Developmental milestones
Chronological age, physical growth and developmental skills usually evolve hand in hand. Just as there are normal ranges for changes in body size with age, so there are ranges over which new skills are acquired. Important developmental stages are called developmental milestones.
When considering developmental milestones:
• The median age is the age when half of a standard population of children achieve that level; it serves as a guide to when stages of development are likely to be reached but does not tell us if the child’s skills are outside the normal range.
• Limit ages are the age by which they should have been achieved. Limit ages are usually 2 standard deviations (SD) from the mean. They are more useful as a guide to whether a child’s development is normal than the median ages. Failure to meet them gives guidance for action regarding more detailed assessment, investigation or intervention.
Median and limit ages
The difference between median and limit ages is shown by considering the age range for the developmental milestone of walking unsupported. The percentage of children who take their first steps unsupported is:
The median age is 12 months and is a guide to the common pattern to expect, although the age range is wide. The limit age is 18 months (2 SDs from the mean). Of those not achieving the limit age, many will be normal late walkers, but a proportion will have an underlying problem, such as cerebral palsy, a primary muscle disorder or global developmental delay. A few may be understimulated from social deprivation. Hence, any child who is not walking by 18 months should be assessed and examined. Thus, 18 months can be set as a ‘limit age’ for children not walking. Setting the limit age earlier may allow earlier identification of problems, but will also increase the number of children labelled as ‘delayed’ who are in fact normal.
Variation in the pattern of development
There is variation in the pattern of development between children. Taking motor development as an example, normal motor development is the progression from immobility to walking, but not all children do so in the same way. While most achieve mobility by crawling (83%), some bottom-shuffle and others crawl with their abdomen on the floor, so-called commando crawling (creeping) (Fig. 3.3). A very few just stand up and walk. The locomotor pattern (crawling, creeping, shuffling, just standing up) determines the age of sitting, standing and walking.

The limit age of 18 months for walking applies predominantly to children who have had crawling as their early mobility pattern. Children who bottom-shuffle or commando crawl tend to walk later than crawlers, so that within those not walking at 18 months there will be some children who demonstrate a locomotor variant pattern, with their developmental progress still being normal. For example, of children who become mobile by bottom-shuffling, 50% will walk independently by 18 months and 97.5% by 27 months of age, with even later ages for those who initially commando crawl.
Adjusting for prematurity
If a child has been born preterm, this should be allowed for when assessing developmental age by calculating it from the expected date of delivery. Thus the anticipated developmental skills of a 9-month-old baby (chronological age) born 3 months early at 28 weeks’ gestation are more like those of a 6-month-old baby (corrected age). Correction is not required after about 2 years of age when the number of weeks early the child was born no longer represents a significant proportion of the child’s life.
Is development normal?
When evaluating a child’s developmental progress and considering whether it is normal or not:
• Concentrate on each field of development (gross motor; vision and fine motor; hearing, speech and language; social, emotional and behavioural) separately.
• Consider the developmental pattern by thinking longitudinally and separately about each developmental field. Ask about the sequence of skills achieved as well as those skills to be anticipated shortly.
• Determine the level the child has reached for each skill field.
• Now relate the progress of each developmental field to the others. Is the child progressing at a similar rate through each skill field, or does one or more field of development lag behind the others?
• Then relate the child’s developmental achievements to age (chronological or corrected).
This will enable you to decide if the child’s developmental progress is normal or delayed. Normal development implies steady progress in all four developmental fields with acquisition of skills occurring before limit ages are reached. If there is developmental delay, does it affect all four developmental fields (global delay), or one or more developmental field only (specific developmental delay)? As children grow older and acquire further skills, it becomes easier to make a more accurate assessment of their abilities and developmental status.
Pattern of child development
This is shown pictorially for each field of development, including key developmental milestones and limit ages:
• Gross motor development (Fig. 3.4 and Table 3.1)
• Vision and fine motor (Fig. 3.5)

• Hearing, speech and language (Fig. 3.6)

In order to screen a young child’s development, it is necessary to know only a limited number of key developmental milestones and their limit ages.
Cognitive development
Cognition refers to higher mental function. This evolves with age. In infancy, thought processes are centred around immediate experiences. The thought processes of preschool children (which have been called preoperational thought by Piaget, who described children’s intellectual development) tend to be that:
• they are the centre of the world
• inanimate objects are alive and have feelings and motives
• events have a magical element
• everything has a purpose. Toys and other objects are used in imaginative play as aids to thought, to help make sense of experience and social relationships.
In middle-school children, the dominant mode of thought is practical and orderly, tied to immediate circumstances and specific experiences. This has been called operational thought.
It is only in the mid-teens that an adult style of abstract thought (formal operational thought) begins to develop, with the ability for abstract reasoning, testing hypotheses and manipulating abstract concepts.