Chapter 1 An Introduction to Lifespan Development 7
Checkpoint
1. What is human development?
2. List six skills children often learn during the fi rst fi ve years of life.
3. When do people often learn independence and begin to process more
complex ideas?
Types of Development
The average lifespan in the 21st Century is 78 years. That is almost 30 years
longer than the life expectancy in the previous century. Nutrition, medicine,
better sanitization, and lifestyles have all contributed to this increased lifespan.
People change and develop over their lifespan in several major ways. They
change physically, cognitively, socially, and emotionally (hereafter referred to as
socio-emotional development).
In each stage of life, people can be described by their physical, cognitive, and
socio-emotional differences. In later chapters, you will learn about typical physi-
cal, cognitive, and socio-emotional development from birth through old age.
Here are a few highlights.
Physical Development
Throughout life, people change in size and
height. People often judge children’s ages by the
way their bodies look in height and overall propor-
tion of parts. This is called physical development—
the changes in size, body composition, chemical
make-up, and height that occur as humans develop
from birth to adulthood. Although all people grow
and change physically at different rates, scientists
and researchers agree on general guidelines or
expectations of which changes are common in each
stage of development.
Babies gain weight and grow in length rapidly.
Their teeth become visible as they break through
the gums, 1-2. These first baby teeth fall out and
new ones replace them. Their hair thickens and
becomes more plentiful. In younger children, the
head is proportionally larger in relation to the
body than in older children.
In the teen years, growth in both height and
weight continue. Bodies change in ways beyond
height and size, however. As a teen enters puberty,
his or her body begins to change in preparation for
possible parenthood. Muscle and fat tissue begin
to redistribute and accumulate. Chemical changes
also occur within the body.
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1-2
This baby is beginning to grow his
first teeth, which is a physical sign of
development.