Have you ever heard someone say that their child is like a sponge? Or perhaps comment
on how quickly their kid is growing up? These phrases and others like them relate to how
children seem to soak up knowledge and change rapidly over their first few years of life.
Kids change a lot during childhood, and what happens during this time period can have a lasting
impact on their behaviors in adulthood. The field of developmental psychology tries to explain
how and why people’s thoughts, feelings, and behaviors change over their lifetime,
with a particular emphasis on childhood, since this is when a lot of important changes occur,
and these changes predict later adult psychology. Developmental psychology is an enormous topic that
would be impossible to cover in a single video, so let’s simply hit some highlights for now.
Let’s start with the basics. How do psychologists study development? Psychologists have a few
different techniques to answer different questions. Let’s say you’re interested in
the development of morality. How does it change across one’s lifetime, and when does it develop?
To answer the first question, you would want to perform a longitudinal study and follow the same
group of people as they grow up. You would take a group of young children, say four-year olds,
and ask them what they think right and wrong means. Then you would bring them back into the
lab every few years, ask them the same questions, and see how their answers change. If you cared
less about how morality changes across development and more about when children develop morality,
you would probably do a cross-sectional study or an age of onset study. For a cross-sectional
study, you would take a few groups of kids at different ages and see how their behaviors differ.
How does the morality of eight-year olds differ from that of six-year olds and from that of
four-year olds? An age of onset study is similar in that you’re studying different age groups,
but in this case, you don’t compare the age groups to each other. Instead, you ask what
do four-year olds do in this morality task? What about six-year olds? What about eight-year olds?
Finally, let’s pretend you’re interested in how growing up at different times
might affect morality. You would do a generational, or cohort, study in this case,
and ask how people who grew up in different times thought about morality. Do boomers
have the same ideas about morality as millennials? If not, how are they different?
Now that we have a basic understanding of how developmental psychologists tackle developmental
questions, let’s talk about a debate you may have heard of: nature vs. nurture. This debate
is about what has the biggest influence on child development. Is your development constrained by
nature, where the genes you possess control your behavior and psychology? Or is your development
more influenced by nurture, meaning everything else that could influence your behavior,
like learned associations from experience, the social and cultural environment,
or your interactions with other people? Well, the answer is… both! The idea of nature vs.
nurture is a false dichotomy. We don’t have to pit nature and nurture against each other.
Development is influenced by both your genes and the environment you’re in. In fact,
your environment and social interactions can influence which genes are expressed
and how they are expressed, ultimately affecting your behavior. While some behaviors may be more
influenced by genetic factors than others, and vice versa, development as a whole is affected
significantly by both nature, the genes you have, and nurture, the environment you’re in.
Let’s move on to actually talking about kids and how they develop. An important thing to note is
that children are not just really dumb adults. Children occupy a very specific developmental
niche. The way they view and interact with the world is inherently different from adults,
and will change as the child grows and develops. This means that kids think and
reason differently than adults and will see the world in different ways. As a child grows, they
build up their knowledge about the world through their experiences. They are actively experimenting
with the world around them, and from the results, building an understanding of how the world works.
To get a framework around this process, we are going to focus on a theory that
is commonly used to describe child development known as “Piaget’s Stages.” Jean Piaget was a
psychologist in the early 1900s who proposed a theory to describe how childrens’ intelligence
grows and changes. His theory relies on the idea that cognitive abilities build upon one another.
As we go through these stages, we will reference some approximate ages at which children go through
a particular stage. Psychologists today generally think that all children go through these stages
in this order and on average at these time periods, but there is some variation. Certain
kids move through the stages faster than others, and these kids aren’t necessarily
‘smarter’, it’s just some natural variation. Let’s move through Piaget’s stages now. The first
stage is called the sensorimotor stage, and this usually occurs between birth and two years old.
This stage is characterized by an enormous amount of growth and learning. We all go from being an
infant who is lightly interacting with their world through reflexes, to a toddler who is actively
moving and exploring. Kids in this stage use the skills and abilities that they are born with,
like looking, grasping, and listening, to explore their environment. They use their senses and motor
abilities to learn through trial and error about the world around them. It’s during the
sensorimotor stage that children begin to learn that their actions can cause specific reactions.
For example, they might begin to realize that when they shake a rattle, it makes a pleasing
sound. Or that pushing a light switch causes a light to turn on or off. They also might try
to make different sounds to see if they can get a response from a caregiver. An important cognitive
milestone in this stage is the development of object permanence. Very young infants do not have
object permanence, that is, they don’t understand that objects continue to exist even when they
can’t be seen or heard. This is why young infants will act surprised during a game of peek-a-boo.
When you hide behind your hands, the infants believe that you are actually disappearing.
Older infants that have developed object permanence will learn and understand that you
continue to exist even when they can’t see you. The next stage is the preoperational stage,
which happens around two years old to seven years old. In this stage, children become proficient in
language. They also begin to think symbolically, as you know if you’ve ever played pretend with
a child. They can use an object to represent something else, like pretending a broom is a
horse if they want to be riding a horse. Kids in this stage still struggle with some logical tasks,
and often struggle with adopting the view of other people. They may think that everyone
sees things as they see them. They also struggle with conservation. For example, say you have two
identical containers with equal amounts of liquid. Then you pour the liquid from one container into a
differently shaped cup, like a tall, thin cup or a short, wide cup. Even though the amount of liquid
did not change, children will say that there is more liquid in whichever cup appears to be fuller.
The third stage is the concrete operational stage, which takes place between around seven
and eleven years old. Unlike in the previous stage, children now understand conservation.
They know that breaking a candy bar into more pieces does not mean there is more candy.
Children in this stage also begin to develop logical thought. Although they still tend to
be very concrete in their thinking, children are beginning to excel at certain logical tasks
like inductive logic. This means that they can go from a specific experience to a general principle.
Say you notice that every time you’re around a cat, you get itchy eyes and a runny nose. Children
who have mastered inductive logic would then be able to induce that you are allergic to cats.
The fourth and final stage of Piaget’s stages is the formal operational stage, occurring when kids
are around twelve years old and older. Children and young adults in this stage have the capacity
for much more sophisticated thought. They can think about abstract and theoretical concepts, and
can come up with creative solutions to problems using logic. In this stage, a child doesn’t need
actual concrete objects to answer questions via trial and error. Instead, they can perform mental
operations in the head using abstract terms. For example, kids at this stage can work through the
following question in their head: “If you imagine something made up of two quantities, and the
whole thing remains the same when one quantity is increased, what happens to the second quantity?”
Piaget’s four stages help us understand how children develop cognitively across development.
Importantly, Piaget didn’t think that kids develop by simply adding more knowledge to their brains
as they grow up. Instead, the quality of how they think changes as they progress through the stages.
A seven-year old thinks differently than they did at age two.
Today, psychologists generally appreciate and accept Piaget’s stages, with some caveats. As we
mentioned earlier, there is a lot of variation in how children develop. Not all children will
move through these stages at the same times. Still, Piaget’s stages provide a useful framework
for thinking about child development and they played a huge role in influencing
the field of developmental psychology. His theory also helped psychologists realize
that kids think differently than adults, and that they aren’t just smaller versions of adults.
There’s a lot more we could say about different topics in developmental psychology,
and perhaps later in the series we will go deeper with this fascinating subject.
But for now we’re going to move on to the next topic in the series, personality.