Definition of Psychology: Types, Concepts, & Examples

By Nathalie Boutros, Ph.D.
​Reviewed by Tchiki Davis, M.A., Ph.D.

What is psychology? In this article, we’ll define psychology, list different approaches to psychology, and briefly review the origins of the discipline.

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Why do people say the things that they say and do the things that they do? Why is your toddler so endlessly entertained by peek-a-boo? Why did you eat that third slice of cake even though you know you shouldn’t have? Why did that other driver cut you off so aggressively? Why did your coworker lie to you about the progress he made on the project? Why did that customer leave such a huge tip on their tiny food bill? 

Most of us puzzle over the causes and explanations of the things that we see other people do and the things that we find ourselves doing. Psychology is the systematic, orderly pursuit of answers to questions about the causes and drivers of human (and animal) behavior. As we will see in this article, the causes of human behavior can be found on several different levels: biology, the environment, mental processes, social structures, and more. We will review these levels of explanation, as well as others, and we will briefly go over the early history of psychology as a systematic, evidence-based science.

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What Is the Definition of Psychology? (A Definition)

Broadly, psychology is the systematic study of the mind and behavior (Plotnik & Kouyoumdjian, 2011). Although this definition is simple, it covers a lot. Psychology studies the mental processes implicated in mental illness and the mental processes responsible for normal functioning. Psychology studies sensation, for example in finding the smallest detectable difference between two colors. Psychology also studies perception, for example explaining how optical and other sensory illusions are created. 

Psychology studies memory, motivation, learning, and cognition. Psychology studies social processes, for example by explaining how complex decisions can be influenced by groups. Psychology covers developmental processes, studying how thinking and behavior change throughout the life cycle. Psychology studies how the brain, the body, and the genome are involved in all of these aspects of the mind and behavior. And of course, psychology studies how each of the above-listed factors influence and interact with one another. 

Definition of psychologists
Given such a broad domain, no single psychologist can be an expert in all of psychology. Psychologists specialize in different areas of study and in different approaches to the mind and behavior. Some psychologists take a biological approach to the discipline, seeking explanations for the mind and behavior in brain structures, neurochemicals, hormones, and the genome. Other psychologists take an approach more akin to computer science, describing the logical rules and algorithms that define thought and behavior. Yet others look to the environment to explain behavior, either in the consequences that follow responses or in the social and familial structures that shape schemas and worldviews. 

Although the history of psychology has seen several disputes over which approach is best, no approach necessarily invalidates or discredits any of the others. Human (and animal) behavior is so complex and multiply-determined that explanations at several levels can all provide useful and insightful information about the mind, the brain, and behavior. 

Definition of Psychology According to The APA

The American Psychological Association (APA) is a professional and scientific organization that represents both research and clinical psychologists. The APA’s definition of psychology is very broad. According to the APA’s website (American Psychological Association, n.d.) “psychology” is the study of both normal and abnormal functioning. The discipline of psychology seeks to uncover the relationships between the mind, the brain, behavior, and the environment. Psychology is an experimental science, a clinical practice, and the application of psychological knowledge across environments including schools, workplaces, athletic settings, and the justice system.

Types of Psychology and Their Definitions

Because psychology, as the study of mind and behavior, is so broad, it has been broken down into sub-disciplines and sub-fields that focus on specific aspects of the mind or behavior. Although there are countless specialties and areas of expertise in psychology, the field can generally be broken down into eight sub-disciplines (Plotnick & Kouyoumdjian, 2011).
​

• Clinical/Counseling Psychology: This area of psychology is concerned with the assessment and treatment of mental illness and psychological dysfunction. The scope of psychological dysfunction that clinical psychologists are concerned with is very broad. It includes potentially serious mental illnesses like bipolar disorder and schizophrenia and more common psychological difficulties that a majority of people will face at some point in their lives, for example, grief, stress, and anxiety.
• Developmental Psychology: Developmental psychologists are interested in how people change and develop as they move through life. How do mental processes, emotions, social behaviors, morality, temperament, and the several other aspects that make up a person change from infancy, through early to late childhood, into adolescence, and throughout early, mid, and late adulthood?
• Social Psychology: This type of psychology studies how people are influenced by group dynamics and social interactions. Social psychologists study things like stereotypes, prejudices, conformity, aggression, and attraction. Philip Zimbardo is a social psychologist perhaps best known for his 1971 Stanford Prison Experiment. This experiment, described in the video below, found that regular people were capable of acts of cruelty when placed into specific circumstances that encouraged such behavior. In the video below he explains the social psychology of evil, how group processes and social dynamics can cause people to behave in cruel and disturbing ways. Please note that this video contains disturbing content including graphic images of torture victims. ​​

Video: The Psychology of Evil | Philip Zimbardo

• Experimental Psychology: This area of psychology is concerned with uncovering the fundamentals of learning, memory, sensation, perception, decision-making, motivation, emotion, and other mental and behavioral phenomena. Usually, experimental psychologists conduct tightly controlled laboratory experiments where they manipulate one variable at a time in order to draw conclusions about the specific effects of that one variable. For example, in order to determine the effect of the neurotransmitter dopamine on risk-taking, adult volunteers in a 2012 study were given either a drug that increased dopamine transmission or a placebo (Campbell-Meiklejohn et al., 2012). The volunteers then all performed the same laboratory task where they were given the opportunity to gamble. The researchers found that people given the dopamine-inducing drug were more likely to gamble than the people given the placebo. The experiment and environment were identical for all study participants, allowing the researchers to confidently conclude that the dopamine drug, the only point of difference across the two groups, was responsible for the differences in risk-taking.
• Biological Psychology: This type of psychology studies how the physics and chemistry of the brain, as well as the genes that code for specific proteins, all interact with the wider world and the environment to produce mental and behavioral events. Biological psychologists sometimes study how drugs or neurochemicals affect behavior, as in the above study on dopamine and risky choice. They also study the effects on the mind and behavior of naturally occurring differences in the brain, acquired brain damage, sleep deprivation, hunger, thirst, stress, and other manipulations of the brain or the body.
• Psychometrics: This area of psychology is concerned with creating, administering, interpreting, and evaluating psychological tests. Tests can measure a person’s skills, abilities, intelligence, personality, or psychological health. If you have ever taken a test where you answered questions stating the degree to which you agree with a statement (e.g., strongly agree, agree, disagree, strongly disagree) or how often you have behaved in a specific way (e.g., often, sometimes, rarely, never), you may have taken a test designed by a psychometrician.
• Cognitive Psychology: Cognitive psychology is concerned with how people process, store, and then retrieve information. This includes memory, language, problem-solving, decision-making, and creativity. 
• Industrial/Organizational Psychology: This type of psychology is concerned with how people behave and are influenced by their professional or work environments. These psychologists may study the factors that contribute to employee happiness and job satisfaction.

What Are the 5 Concepts of Psychology?

Psychology tries to explain mental events and observable behavior. Explanations can exist at several levels of understanding and these levels of understanding are sometimes called approaches, perspectives, or concepts. There are at least five approaches (Plotnick & Kouyoumdjian, 2011). 

The Biological Approach: This perspective focuses on how genes, neurochemicals, hormones, and the nervous system interact with the environment to create what we call the mind and behavior. How do physiology and genetics influence learning, memory, emotions, drives, motivations, and personality as well as other traits and tendencies?

For example, a biological approach to mental illness might consider the afflicted person’s genome, their neurochemistry, and any anatomical features of specific brain structures. Depression, for example, is said to be caused by dysfunction of specific brain structures including the amygdala, cingulate cortex, and nucleus accumbens. Depression is also partly attributed to specific genes including GNB3 and MTHFR, and to deficits in the functioning of specific neurotransmitters including dopamine and serotonin (Krishnan & Nestler, 2010).

The Cognitive Approach: This approach to psychology focuses on the processes by which a person acquires, stores, and then uses information. How does the information come to influence mental and behavioral events? How are your perceptions, attention, memory, thoughts, beliefs, emotions, and behaviors all affected by the information that you have stored and the ways that this information is processed? The cognitive approach to mental health may consider the dysfunctional thought patterns that contribute to a mental illness. For example, depression may be partly caused by overfocusing on negative events (rumination), and insensitivity to positive events (Gotlib & Joormann, 2010).

The Behavioral Approach: This approach to psychology considers how the environment, in the form of antecedents (signals) and consequences (rewards and punishments), influences behavior. How do the consequences of a behavior influence both the learning and the expression of that behavior? Behavioral theories of depression for example propose that the low mood and dysphoria that characterize depression may be caused by a relative absence of enjoyable and pleasant activities and experiences and that increasing these activities may decrease many of the symptoms of depression (Cuijpers et al., 2007).

The Psychoanalytic Approach: This conception of Psychology, which is also sometimes called the psychodynamic approach, focuses on childhood experiences. How do the experiences and relationships of your childhood influence your behaviors, thoughts, emotions, and personality in adulthood?

This approach, which was pioneered by Sigmund Freud in the late nineteenth century, posits a large role for unconscious desires, motivations, and fears in driving thoughts and behaviors. A psychoanalytic perspective on depression may consider how the afflicted person’s past influences his or her current thought and behavior patterns and how the afflicted person interprets and understands the world. It would then go on to develop an understanding of how the person’s specific point of view contributes to the symptoms of depression (Driessen et al., 2015).

The Humanistic Approach: This approach to psychology focuses on the potential that each person has to grow, develop, and determine his or her own future. The humanistic approach considers personal growth, intrinsic worth, and self-fulfillment. Humanistic psychology recognizes that people may need to struggle to reach their potential but that each individual has a high degree of control over his or her own future.

The humanistic approach considers positive aspects of humanity including the capacity for art, relationship-building, freedom, and creativity. A humanistic approach to depression may start with the premise that human beings are “self-actualizing”, and that people can drive their own development and potential. Importantly, a humanistic approach emphasizes the individualism of the person, meaning that specific therapies or treatments aren’t prescribed in a “one size fits all” manner that may be more characteristic of the other approaches to psychology.

​The relationship that the individual has with his or her therapist is important. Empathy and unconditional positive regard from the therapist are said to be key to helping the afflicted person find his or her way out of the depression. Humanistic therapy may focus on creating an environment that can encourage the client to grow in ways that he or she defines and determines. This can happen by encouraging insight, acceptance, change, and personal growth. Although the depressive symptoms may not be directly or specifically addressed, the symptoms of depression may decrease through increases in self-acceptance and personal growth (Davies et al., 2010).

When was Psychology Started?

People have been thinking about the causes and mechanisms behind human cognition and behavior for millennia. Hippocrates developed his theory of the four humors over 2500 years ago. Briefly, this ancient theory claims, among other things, that personality and temperament are determined by the relative levels of four bodily humors: blood, yellow bile, black bile, and phlegm. People with a lot of blood were said to be courageous and playful, those with high levels of yellow bile were said to be ambitious and restless, people high in black bile were said to be quiet and serious, and those with high levels of phlegm were said to be calm and thoughtful (Kalachanis & Michailidis, 2015).

Theories like the humoral theory of personality were attempts to uncover the causes of human behavior and cognition and may be considered precursors to modern psychology. Several ancient religious and spiritual traditions also contain elements that may be considered precursors to modern psychology, for example, ideas of demonic possession. These theories all sought to explain some aspect of human behavior, either typical or dysfunctional. Notably, these types of theories all recognize that human behavior has a cause and that the cause of human behavior is knowable. However, these theories are generally not characterized by the scientific, evidence-based approach that is present throughout all modern psychology across theoretical approaches.

Modern Psychology may be said to have started during the seventeenth century, at around the same time that biology and medicine were emerging as scientific disciplines. For example, the French philosopher, mathematician, and scientist Rene Descartes proposed that many human instincts and behaviors arise from impulses in the brain (Alanen, 1989). Other, more complex mental and behavioral events were said to arise from the combined effects of the physical body and a non-physical soul. Descartes even proposed a specific neural home for the soul, the pineal gland which is located deep within the brain.

Despite these early philosophical, religious, and even almost scientific approaches to psychology, psychology as an independent, scientific, evidence-based study of the human mind and behavior did not really emerge until the late nineteenth century.

Who Is Considered the Father of Psychology?

After millennia of musing about the causes of human behavior and mental illness, physicians, philosophers, and scientists in the late 1800s started to systematically study behavior and mental processes. Although several people were working on what would later become psychology, the person most often called the father of psychology is Wilhelm Wundt.

Definition of Psychology According to Wilhelm Wundt

Wilhelm Wundt was a nineteenth-century German physician who established what we now consider to be the world’s first psychology laboratory in 1879 (Asthana, 2015). In this lab, people acted as both the subject and the experimenter in their own experiments. Through a method called introspection, people would, for example, listen to the ticking of a metronome and then report on their own sensations of hearing and perceiving the clicks.

Wundt developed an approach that came to be called structuralism - the belief that all of our thoughts and other mental processes can be broken down into simpler component parts. We can then build from these simple component parts to understand mental processes. In the same way that a chemist can understand how a chemical compound will behave by understanding the elements that make up the compound, Wundt proposed that a psychologist could understand how a person would behave by understanding the psychological elements that make up the mind. Wundt and his followers sought to discover a periodic table of psychological elements.

Definition of Psychology According to William James

William James was a nineteenth-century philosopher who created and taught the world’s first Psychology class at Harvard University in 1875. According to his seminal 1200-page 1890 work “The Principles of Psychology”, psychology is “the Science of Mental Life”. He went on to specify that this definition covers a wide range of topics including “feelings, desires, cognitions, reasonings, decisions, and the like”.

James’ approach to psychology was more functional than Wundt’s structural approach. Rather than considering mental processes as psychological compounds made up of simpler elements, functionalism considers mental processes as tools that help a person function and adapt to changing environments (Green, 2009). James’ functionalism considers mental processes in light of the function, or purpose that they serve. 

James was influenced by Charles Darwin and his theory of evolution and his functional approach incorporates ideas from physiology and considers evolutionary history. James developed an example to illustrate his functional approach. In this example, imagine that you are in the woods and come across a bear - you become frightened and you run away. Although it may seem that you run away because you are frightened, James proposed that the chain of causality actually goes the other way. Namely, you see the bear and then run away. Your body then interprets the sensations that come with running away as fear. This focus on the functions of psychological processes applies to not only emotions, but also to most other mental processes including cognition, consciousness, and behavior. James’ functionalism states that the explanations for all mental processes, including these higher-order ones, lie in the functions that they serve.

​Definition of Psychology According to Sigmund Freud

Sigmund Freud was a doctor and neuroscientist in the late 19th and early twentieth century who is most notably remembered as the founder of psychodynamics, or the idea that there exist mental events that drive behavior without being available to conscious awareness. Prior to Freud, scientists and physicians did not generally accept that memories, thoughts, impulses, emotions, ideas, and experiences could influence thoughts and behavior without being available to conscious awareness (Westen, 1998). 

Freud claimed that these unconscious mental processes were influenced by experiences and relationships, especially early life experiences and relationships. Notably, religious and philosophical thinkers had earlier proposed that there may be unknown drivers of human thoughts and behaviors, however, these drivers tended to be religious (e.g. angels, demons) or otherwise spiritual (e.g. curses, ghosts). Freud was revolutionary in placing these unconscious drivers firmly in the physical as opposed to the metaphysical realm. Although many of the specifics of Freud’s theories and ideas have been refuted by modern approaches to psychology, the core acceptance that there is more to the mind than what we are consciously aware of continues to be one of the foundations of modern psychology. 

Articles Related to The Definition of Psychology​

​Want to learn more? Check out these articles:

• Behavioral Psychology: Definition, Theories, & Examples
• Positive Psychology: Definition, Theories, and Examples
• Psychological Health: Definition, Examples, & How to Improve It​​​​​​​​​​​​​

Books Related to The Definition of Psychology​

If you’d like to keep learning more, here are a few books that you might be interested in.

• The Definition of Psychology (Century Psychology Series)
• Psychology: A Complete Introduction
• A Degree in a Book: Psychology: Everything You Need to Know to Master the Subject - in One Book!
• The Definition of Psychology. An Introduction of Psychological Systems.

Final Thoughts on The Definition of Psychology

For most of human history, ideas about the mind and behavior, when they existed, were rooted in religion and philosophy and were not supported by scientific or empirical evidence. Psychology emerged as the systematic, evidence-based study of mind and behavior over 100 years ago. Since then it has exploded into several specialties and subdisciplines, uncovering causes of human behavior in biology, the environment, the social world, and logical rules of reasoning and cognition.

​In a comparatively short time, the science of psychology has made huge strides in explaining everyday behavior and cognition as well as the troubling mental and behavioral events that characterize mental illness. The field continues to grow and develop and psychologists continue to make discoveries and connections and find new ways to help and support people who find themselves facing psychological distress.

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References

• ​​Alanen, L. (1989). Descartes's dualism and the philosophy of mind. Revue de Métaphysique et de Morale, 391-413.
• American Psychological Association (n.d.). About APA. https://www.apa.org/about
• Asthana, H. S. (2015). Wilhelm wundt. Psychological Studies, 60(2), 244-248.
• Campbell-Meiklejohn, D., Simonsen, A., Scheel-Krüger, J., Wohlert, V., Gjerløff, T., Frith, C. D., ... & Møller, A. (2012). In for a penny, in for a pound: methylphenidate reduces the inhibitory effect of high stakes on persistent risky choice. Journal of neuroscience, 32(38), 13032-13038.
• Cuijpers, P., Van Straten, A., & Warmerdam, L. (2007). Behavioral activation treatments of depression: A meta-analysis. Clinical psychology review, 27(3), 318-326.
• Davies, P., Hunot, V., Moore, T. H., Caldwell, D., Jones, H., Lewis, G., & Churchill, R. (2010). Humanistic therapies versus treatment as usual for depression. The Cochrane database of systematic reviews, (9).
• Driessen, E., Hegelmaier, L. M., Abbass, A. A., Barber, J. P., Dekker, J. J., Van, H. L., ... & Cuijpers, P. (2015). The efficacy of short-term psychodynamic psychotherapy for depression: A meta-analysis update. Clinical psychology review, 42, 1-15.
• Gotlib, I. H., & Joormann, J. (2010). Cognition and depression: current status and future directions. Annual review of clinical psychology, 6, 285-312.
• Green, C. D. (2009). Darwinian theory, functionalism, and the first American psychological revolution. American Psychologist, 64(2), 75.
• Kalachanis, K., & Michailidis, I. E. (2015). The Hippocratic view on humors and human temperament. European Journal of Social Behaviour, 2(2), 1-5.
• Krishnan, V., & Nestler, E. J. (2010). Linking molecules to mood: new insight into the biology of depression. American Journal of Psychiatry, 167(11), 1305-1320.
• Plotnik, R. & Kouyoumdjian, H. (2011). Introduction to Psychology (ninth edition). Wadsworth Cenage Learning.
• Westen, D. (1998). The scientific legacy of Sigmund Freud: Toward a psychodynamically informed psychological science. Psychological bulletin, 124(3), 333.

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