by Chris Woodford. Last updated: July 6, 2021.
Why do we do the things we do? Why do some people like hot chocolate while others prefer coffee? Why do some live to
surf while others would rather stay home and read a book? How can some of us put
a name to every single person we've ever met while others struggle
even to remember our own telephone number? Why do some people
always seem happy and successful while others see no choice but to
end their painful lives in suicide? These are the sorts of questions
we can try to answer through psychology: the science of human
behavior. In this short article, we'll briefly explore the different
branches of psychology and get a quick overview of the kinds of
things psychologists do.
Photo: Everything you do, think, and feel involves your brain, shown
here as a 3D-printed model. Understanding how the brain works, how it gives rise to the mind, and why it makes us do the things we do is the prime goal of psychology. Photo courtesy of Nevit Dilmen, NIH 3D Print Exchange, National Institutes of Health, published on Flickr under a Creative Commons Licence.
What are the different kinds of psychology?
We can divide psychology into two big areas called experimental psychology and social psychology.
- Experimental psychology uses classic, laboratory-based, scientific methods to
study human behavior: it uses similar techniques to physics,
chemistry, or biology, often carried out in a lab, except that
instead of studying light rays, chemical reactions, or beetles, the
experiments involve ourselves and other people.
- Social psychology tends to study how people behave in real-world
situations—for example, how people react to advertisements, why they commit crimes, and how we can work more efficiently in
offices and factories. Social psychology doesn't always involve experiments; it might be based on questionnaires or
Of course, we can study social psychology in a lab using rigorous
experiments, just as we can carry out meticulous experiments in the real world; the division I've drawn between experimental and social
psychology is arbitrary and artificial, but it reflects the way
psychology is often taught in schools and colleges, and how it's
written up in textbooks and scientific papers. The reason for that is
largely historical: in the late 19th-century, when psychology was
still a very new field, psychologists were keen to be taken seriously
as scientists, so they tried to adopt scientific methods to cloak the
things they studied in respectability. To this day, there's a certain
stigma attached to social psychology and sociology (the study of how
individuals and groups behave in society); whether fairly or not,
some people see them as soft sciences lacking academic rigor.
Branches of psychology
Humans are the most complex of all the animals, which explains why
psychology is such a vast subject. Within the psychology department
of a typical university, you'll find people working in a huge range
of different areas. There are people who study perception (such as
how our eyes and ears work), learning (how we develop as children and
how we make sense of the world as adults), memory (why we remember
and how we forget), language, thinking, and reasoning. While some
psychologists study "normal" human behavior, others specialize in
"abnormal" psychology, which includes how people behave when
their brains are damaged or degenerate over time and what causes
psychiatric disorders. Social psychologists study everything from the
best way to design a computer mouse to whether we can really trust
the evidence we get from people who witness crimes. Let's look at the
various branches of psychology in turn, in a bit more detail.
You can think of people as living machines who receive information from
the world, process it in various ways, and then act on it. In the
mid-20 century, it was fashionable to talk about animals (including
people) receiving a stimulus through their senses (maybe seeing a
chocolate-chip cookie appearing in front of you), which then led to
some kind of response (salivating and reaching out); according to a
school of thought known as behaviorism, human behavior was all
about the way a certain stimulus produced an appropriate response
(and exactly what went on inside the brain to make the connection
wasn't thought to be especially important: behaviorism was literally
Since the 1960s and 1970s, psychologists have tended
to view the human brain as a kind of computer, taking in information
as "input," processing and storing it in various ways, and then
producing "output" (some kind of visible behavior); this approach
is known as cognitive psychology and we'll consider it again a
little later. However you react to the world, your behavior usually
starts with sensory perception: the way your five main senses
(vision, hearing, smell, touch, and taste), plus other, lesser-known
sensory abilities such as proprioception (your sense of where your
limbs are and how your body is moving), feed information into your
Photo: A huge part of your brain is devoted to processing information gathered by your eyes.
For most people, vision is easily the most important sense, closely
followed by hearing; that also explains why perceptual psychologists
have traditionally devoted most effort to studying vision, closely
followed by hearing (comparatively speaking, the other senses have
barely been explored at all). Most of us assume that we see with our
eyes, but it's far more accurate to say that we see with our eyes and
our brains. While we can't see without our eyes, it's also true that
our brains carry out a huge amount of processing on the sensory
impressions they receive—and in all kinds of interesting ways. One
very obvious example is that we see things in three dimensions using
separate, two-dimensional images that our brain fuses together from
our two eyes. But we also see things based on what we expect to see,
which is what causes most of the things we call optical illusions;
for example, we see faces in clouds because our brains try to make
sense of the world very quickly based on the things we've seen in the
past (an awful lot of faces), the things we expect to see in the
future (an awful lot more faces), and the things that matter most to
us (the faces of people we love, work with, and have to interact
with). We can get some idea of just how complex the human visual
system is by considering how little progress computer scientists and
robot engineers have made designing machines that can "see" in
anything like the same way. Why are our own brains so good at seeing?
It's (crudely) estimated that something like a third to a half of the cortex (the outer and,
in evolutionary terms, "newest" part of the human brain) is devoted to
That's a very impressive illustration of the sheer complexity of making sense of
the world entirely by studying light rays that enter two big holes in
One of the things that marks out humans from "lesser" creatures is our
ability to make sense of our environment and learn from it. It's
obviously untrue to suggest that humans are the only creatures that
learn things: you can teach a chimpanzee to use a symbolic language,
you can train a dog not to defecate on your carpet, a
quickly learn to run through a maze to reach a food reward, and even
a simple sea-slug can learn a couple of basic tricks.
Learning goes hand-in-hand with survival, but it's a surprisingly large and
complex subject. At one end of the spectrum, psychologists study the
process of conditioning, which is how animals come to
associate a particular stimulus with a certain response. One of
the first people to look into this was Russian scientist
(1849–1936), who famously rang a bell when he delivered food to his dogs; eventually,
he found the dogs would salivate simply when he rang the bell, even
when there was no food around, because they'd been conditioned
to associate salivating with the sound of the bell. When behaviorism
was fashionable, some psychologists thought all kinds of complex
human behavior might be broken down into patterns of stimulus
and response. That's why, for example, you often see attempts to
blame violence on TV and in the movies for wider violence in society.
Now we know complex human behavior is much more than a simple
knee-jerk reflex from stimulus to response.
One of the great things about psychology, which differentiates it from older
sciences such as physics and chemistry, is that its relevance to
everyday life is often more immediate and apparent. One branch of the
psychology of learning is called developmental psychology and
it concerns how babies develop into children and adults: for example,
how they learn language, how they turn specific, concrete examples of
things they see around them into much more general, abstract
principles (the rules by which we have to live to survive), and the
relative importance of "nature" (genetic factors—things we're
born with) and "nurture" (environmental factors—things we're
taught and learn). Developmental psychology has played a huge role in
pedagogy and the scientific, theoretical approach to education; it's also a
fascinating subject to study if you're a parent.
Photo: Mirror neurons? Sometimes we mimic one another's behavioral unconsciously, such as when two friends stand next to one another and, quite unawares, adopt exactly the same posture. Psychologists think our brains contain "mirror neurons," which are activated both when we do things and when we see other people doing those things. That encourages us to copy other people's behavior, and possibly explains how we feel empathy with others.
Photo by Kasey Close courtesy of
Thousands of years ago, before humans started to create fixed settlements and
developed agriculture, we lived much like other animals and
day-to-day survival was our only preoccupation. How different things
are now. Although the world's poorest people still experience life as
a horrible daily battle to survive, most of us, thankfully, get to
lead lives that alternate between (reasonably tolerable) work and
(extremely tolerable) pleasure. Both of these things involve using
our brains as much as or more than our bodies; both see us functioning
as living computers—"human information processors"—that take in
information, process or store it in our brains, and then output
results. The way we process and store information is what cognitive
psychologists study. How do we understand a simple sentence whispered
into our ears? How can we remember everything from how to ride a
bicycle to the names, in order, of all the American presidents? And is
there any fundamental difference between these two types of memory
(knowing how to do something, which is called procedural memory, and
knowing facts about the world, which is declarative memory)?
Where behaviorists liked to pretend that "internal mental processes"
didn't matter, didn't exist, or probably both, cognitive psychologists spend
their time teasing out the precise nature of those processes,
typically coming up with flowchart models that break such things as
memory and language processing (a field of its known, often known as
psycholinguistics) into sequences of discrete components.
Applying this to the study of memory, for example, has given us
models of mind that suggest memory breaks into separate long-term and
short-term stores, with the short-term or "working" memory itself
divided into distinct areas that process visual impressions, snippets
of spoken language, and so on.
Artwork: Ulric Neisser's famous caricature of cognitive psychology from his 1976 book Cognition and Reality.
Cognitive psychology is not limited to how we process the structure of
information, but also what information means. The word cognition is a
synonym for thinking and reasoning, two areas that cognitive
psychologists have also studied using computational models. How do we
make informed judgements about things, such as whether one car is a
better buy than another? Why do we live in absolute fear of things
like terrorist attacks but happily cross roads, drive cars, ride
bicycles, drink alcohol, or smoke cigarettes (all of which pose far
greater risk to our safety and health)? Why do we play lotteries when
the chances of winning are so much less than the odds of being struck
by lightning? These are the sorts of questions cognitive
psychologists consider under the broad umbrella of thinking and reasoning.
Photo: The psychology of typography: Thanks to things you've read and seen previously, you read words printed in different fonts (typefaces) with a slightly different meaning and emotion: elegant, relaxed, friendly, imperative, hostile, or whatever it might be. You can emphasize a message you want to get across by choosing the most appropriate font. That's one of the key principles of graphic design—and it happens in your mind, not on the page.
Though related to cognition, intelligence, which we might define as a
general ability to solve problems, is a separate area of study, and
it's much less fashionable than it used to be several decades ago.
There are several reasons for this. From
Sir Cyril Burt (a prominent
British psychologist who allegedly faked research data about his
studies of intelligence) to
William Shockley (the co-inventor of the
transistor who, predictably, became embroiled in controversy when he
dared to suggest that there was a link between
race and intelligence
that made white people intellectually superior to blacks), the study
of intelligence has often proved intensely controversial. The
controversies, though important, distract from a much more fundamental
difficulty: how should we define intelligence and is it even a meaningful
concept? Some cynics have defined intelligence as the mere ability to
pass intelligence tests, but although psychometric testing is
as popular as ever in recruitment for jobs, intelligence tests are
not, and never have been, a predictor of people's ability to live
happy, worthwhile, successful lives.
When you study psychology, it's remarkably easy to forget that most of the
cool and fascinating things you discover happen inside the brain—an
apparently unremarkable organ often compared to "two fistfuls of
porridge." Neuropsychology is all about figuring out how the brain
is structured and how different parts of it have different functions.
One extreme, early example of neuropsychology, known as
famously involved quack doctors claiming they could tell interesting
things about someone's personality by feeling their skull for bumps.
Although the idea seems risible today, the central idea of
phrenology—that the brain is modular, with discrete regions having
specialized functions—is now known to be essentially correct.
However, it's an unhelpful oversimplification to suggest, for
example, that the right half of the brain is dreamily creative while
the left half is clinically rational; for most of the things we do,
many different parts of the brain are involved, either working in
parallel or in complex serial circuits.
Photo: Brain scanners have revolutionized psychology. By showing up the activity inside our brains when we think certain thoughts or do certain things, they can help to reveal which areas of the brain do what. Photo by courtesy of
Warren Grant Magnuson Clinical Center (CC) and US National Institutes of Health (NIH) Image Gallery.
If cognitive psychology can break things like memory or language into
separate areas or processes, is it possible to locate parts of the
brain where those things happen? That's the basic thinking behind a
hugely successful field called cognitive neuropsychology,
which involves trying to map abstract processes and functions
discovered through cognitive psychology onto very concrete areas of
the brain that neuropsychologists have discovered (and vice-versa).
Some psychologists—modern-day mental
Mercators—get carried away in a frenzy to map the brain,
forgetting that the ultimate goal is not to draw a tourist's guide to the inside
of your head but to produce a scientific explanation of the mind: who we are and
why we do the things we do.
While neuropsychologists do study healthy, functioning brains, they also
devote a lot of their time to researching people whose brains have
become damaged through such things as head injuries, strokes, or
degenerative diseases like Alzheimer's. We can discover much about
how things like memory and language processing work by studying what
people can no longer do when specific areas of their brain are
damaged or destroyed. In the most spectacular cases, it's possible to
find people with very localized brain damage who can no longer do
very specific things (for example, recognizing faces or reading
words); we can infer from this that the damaged brain areas play a
key role in whatever function has been lost—and that helps us build
up a map of which parts of the brain do what.
People are hugely diverse and different—that's one of the things that makes
life interesting. While it's difficult to define "normal"
behavior, it's somewhat easier to point to examples of abnormal
behavior, which is harmful to people and those around them.
Neuropsychological problems following brain injuries are one example,
but behavior can also become abnormal for a wide variety of other
reasons, which we might broadly divide into behavioral, cognitive,
and neurochemical/biological. Eating disorders such as anorexia and
bulimia are believed to be largely behavioral and cognitive, for
example: you might develop an eating disorder if you convince
yourself you're fat, after becoming obsessed with skinny catwalk
models. Illnesses such as Parkinson's disease are more to do with
neurochemistry and biology: Parkinson's is believed to occur when nerve cells in the brain
stop producing dopamine, an essential chemical neurotransmitter that sends messages around the brain.
Psychiatric disorders such as depression and schizophrenia are hugely complex and
still imperfectly understood. Depression can occur for many different
reasons, which might be behavioral (you feel nothing you do makes any
difference and become miserable through "learned helplessness"),
cognitive (you analyze the world around you in a way that
persistently makes you unhappy), neurochemical/biological (for one
reason or another, the chemicals or the basic structure of your brain
are geared to unhappiness), or some combination of these things. The
study of schizophrenia has a fascinating history, with attempts to
explain it shifting from anatomical/biological causes, through cognitive and behavioral ones, and back again. Originally described as a kind of premature dementia ("dementia praecox"),
by the 1960s it was being painted (by such figures as R.D.Laing) as a
kind of sane reaction to an insane world, and now it's much more likely to
be considered a consequence of complex, interacting factors such as a person's particular genetic inheritance,
life events, substance use, and brain chemistry.
You'd think understanding the cause of a psychiatric problem would be the
first step toward treating it but, remarkably, psychiatry has often
worked in willful ignorance of what was happening in the mind, partly
through the influence of behaviorism, partly through the challenge of anti-psychiatrists
who refused to believe in what they called the
"myth of mental illness," and also because the underlying
causes of psychiatric problems were genuinely not known. Treatments
for psychiatric disorders were largely doled out on the basis of what
seemed to work and what didn't; if clinical trials found that drugs
cured more depressive patients than, say, group therapy (talking
about your problems with other patients), drugs became the treatment
of choice. It didn't necessarily matter why they worked or how,
providing the patients showed an improvement. That's how hugely
controversial psychiatric treatments such as
removal or destruction of parts of the brain, also called leukotomy) and
(electrical shocks to the brain) became popular in the mid-20th
century. Just as psychology tried to cloak itself in experimental and
scientific rigor, so 20th-century psychiatry latched onto the
respectability of medicine, often masking a substantial ignorance of
how and why disorders actually occurred. Today, thanks to advances in
neurology, neuropsychology, and neurobiology, we have a much clearer
understanding of how the brain works and why it can malfunction—but
many questions remain.
Photo: Psychologists are helping computer scientists to develop emotional robots like this one, pictured at Think Tank, the science museum in Birmingham, England.
How will psychology develop in future?
In the 150 years or so since psychology became a science, huge
amounts have been discovered about why people behave as they do and
how we can relate different aspects of human behavior to what goes on
inside our heads. Even so, teasing out the many, remaining mysteries
of the brain remains one of the last great challenges of science.
Apart from being hugely interesting in its own right, another
important prospect is the discovery of effective treatments for
terrible degenerative diseases such as Parkinson's and Alzheimer's. A
further interesting direction is the development of artificial
intelligence, including computers and robots that can "think" and
act in more humanlike ways. Will probing the mysteries of the mind
help us perfect electro-mechanical rivals who make us obsolete? Or
will the act of developing intelligent machines sharpen our sense of
what it means to be human, making us happier and more fulfilled?
Psychologists, you can be sure, will find the answer!