Psychology (Classical Greek: psyche = "soul" or "mind", logos = "study of") is an academic and applied field involving the study of behaviour, mind and thought and the subconscious neurological bases of behaviour. Psychology also refers to the application of such knowledge to various spheres of human activity, including problems of individuals' daily lives and the treatment of mental illness. It is largely concerned with humans, although the behaviour and mental processes of animals can also be part of psychology research, either as a subject in its own right (e.g. animal cognition and ethology), or somewhat more controversially, as a way of gaining an insight into human psychology by means of comparison (including comparative psychology). Psychology is commonly defined as the science of behaviour and mental processes.

Psychology is conducted both scientifically and non-scientifically, but is to a large extent wholly rigorous. Mainstream psychology is based largely on positivism, using quantitative studies and the scientific method to test and disprove hypotheses, often in an experimental context. Psychology tends to be eclectic, drawing on scientific knowledge from other fields to help explain and understand behaviour. However, not all psychological research methods strictly follow the empirical positivism philosophy. Qualitative research utilizes interpretive techniques and is descriptive in nature, enabling the gathering of rich clinical information unattainable by classical experimentation. Some psychologists, particularly adherents to humanistic psychology, may go as far as completely rejecting a scientific approach, viewing psychology more as an art rather than a rigid science. However, mainstream psychology has a bias towards the scientific method, which is reflected in the dominance of cognitivism as the guiding theoretical framework used by most psychologists to understand thought and behaviour.

Psychology does not necessarily refer to the brain or nervous system and can be framed purely in terms of phenomenological or information processing theories of mind. Increasingly, though, an understanding of brain function is being included in psychological theory and practice, particularly in areas such as artificial intelligence, neuropsychology, and cognitive neuroscience. Psychology is distinct from, though related to, psychiatry, the branch of medicine which treats mental illness.

Psychology differs from sociology, anthropology, economics, and political science, in part, by studying the behaviour of individuals (alone or in groups) rather than the behaviour of the groups or aggregates themselves. Although psychological questions were asked in antiquity (see Aristotle's De Memoria et Reminiscentia or "On Memory and Recollection"), psychology emerged as a separate discipline only recently. The first person to call himself a "psychologist", Wilhelm Wundt, opened the first psychological laboratory in 1879.

History of psychology

The late 19th century marks the start of psychology as a scientific enterprise. The year 1879 is commonly seen as the start of psychology as an independent field of study, because in that year German scientist Wilhelm Wundt founded the first laboratory dedicated exclusively to psychological research in Leipzig, Germany. Other important early contributors to the field include Hermann Ebbinghaus (a pioneer in studies on memory), the Russian Ivan Pavlov (who discovered the learning process of classical conditioning), and the Austrian Sigmund Freud. Freud's influence has been enormous, though more as cultural icon than a force in (scientific) psychology. Freud's basic theories postulated the existence in humans of various unconscious and instinctive "drives", and that the "self" existed as a perpetual battle between the desires and demands of the internal id, ego, and superego.

The mid-20th century saw a rejection of Freud's theories among many psychologists as being too unscientific, as well as a reaction against Edward Titchener's abstract approach to the mind. This led to the formulation of behaviorism by John B. Watson, which was popularized by B.F. Skinner. Behaviorism proposed epistemologically limiting psychological study to overt behavior, since that could be quantified and easily measured. Scientific knowledge of the "mind" was considered too metaphysical, hence impossible to achieve. The final decades of the 20th century have seen the rise of a new interdisciplinary approach to studying human psychology, known collectively as cognitive science. Cognitive science again considers the "mind" as a subject for investigation, using the tools of evolutionary psychology, linguistics, computer science, philosophy, and neurobiology. This new form of investigation has proposed that a wide understanding of the human mind is possible, and that such an understanding may be applied to other research domains, such as artificial intelligence.

Major nineteenth and twentieth century schools of thought

Various schools of thought have argued for a particular model to be used as a guiding theory by which all, or the majority, of human behaviour can be explained. The popularity of these has waxed and waned over time. Some psychologists may think of themselves as adherents to a particular school of thought and reject the others, although most consider each as an approach to understanding the mind, and not necessarily as mutually exclusive theories.

  • Analytical psychology
  • Associationist psychology
  • Behaviourism (see also radical behaviourism)
  • Cognitivism
  • Depth psychology
  • Descriptive psychology
  • Ego psychology
  • Existential psychology
  • Functionalism
  • Genetic epistemology
  • Geneva School
  • Hormic approach
  • Humanistic psychology and phenomenology
  • Individual psychology
  • Symbolic interactionism
  • Phenomenological psychology
  • Psychoanalysis
  • Reactology
  • Reflexology
  • Soviet psychology
  • Structuralism
  • Transactional analysis

Modern psychology

The majority of mainstream psychology is based on a framework derived from cognitive psychology, although the popularity of this paradigm does not exclude others, which are often applied as necessary. Psychologists specialising in certain areas, however, may use the dominant cognitive psychology only rarely if at all.

The testing of different aspects of psychological function is a significant area of contemporary psychology. Psychometric and statistical methods predominate, including various well-known standardised tests as well as those created ad hoc as the situation or experiment requires.

Academic psychologists may focus purely on research and psychological theory, aiming to further psychological understanding in a particular area, while other psychologists may work in applied psychology to deploy such knowledge for immediate and practical benefit. However, these approaches are not mutually exclusive and most psychologists will be involved in both researching and applying psychology at some point during their work. Clinical psychology, among many of the various discipline of psychology, aims at developing in practicing psychologists knowledge of and experience with research and experimental methods which they will continue to build up as well as employ as they treat individual with psychological issues or use psychology to help others.

Contemporary psychology is broad-based and consists of a diverse set of approaches, subject areas, and applications. A comprehensive list is given in the Topics and Divisions sections below. Where an area of interest is considered to need specific training and specialist knowledge (especially in applied areas), psychological associations will typically set up a governing body to manage training requirements. Similarly, requirements may be laid down for university degrees in psychology, so that students acquire an adequate knowledge in a number of areas. Additionally, areas of practical psychology, where psychologists offer treatment to others, may require that psychologists be licensed by government regulatory bodies as well.

While the exact divisions may vary between different countries or institutions, the following areas are usually considered as core subjects or approaches by psychology societies and universities.

Cognitive psychology

Cognitive psychology is a framework in which to understand the mind more than a subject area, although it has traditionally focused on certain aspects of psychology. Perception, learning, problem solving, memory, attention, language and emotion are all well researched areas. Cognitive psychology is based on a school of thought known as cognitivism, whose adherents argue for an information processing model of mental function, informed by positivism and experimental psychology. Techniques and models from cognitive psychology are widely applied and form the mainstay of psychological theories in many areas of both research and applied psychology.

Clinical and counseling psychology

Clinical psychology is the application of psychology to the understanding, treatment, and assessment of psychopathology, behavioural or mental health issues. It has traditionally been associated with counselling and psychotherapy, although modern clinical psychology may take an eclectic approach, including a number of therapeutic approaches. Typically, although working with many of the same clients as psychiatrists, clinical psychologists do not prescribe psychiatric drugs. Some clinical psychologists may focus on the clinical management of patients with brain injury. This is known as clinical neuropsychology and typically involves additional training in brain function.

In recent years and particularly in the United States, a major split has been developing between academic research psychologists in universities and some branches of clinical psychology. Many academic psychologists believe that these clinicians use therapies based on discredited theories and unsupported by empirical evidence of their effectiveness. From the other side, these clinicians believe that the academics are ignoring their experience in dealing with actual patients. The disagreement has resulted in the formation of the American Psychological Society by the research psychologists as a new body distinct from the American Psychological Association.

Developmental and educational psychology

Largely focusing on the development of the human mind through the life span, developmental psychology seeks to understand how people come to perceive, understand, and act within the world and how these perceptions change as we age. This may focus on intellectual, cognitive, neural, social, or moral development. Researchers who study children use a number of unique research methods to engage them in experimental tasks. These tasks often resemble specially designed games and activities that are both enjoyable for the child and scientifically useful. In addition to studying children, developmental psychologists also study other times of rapid change (such as adolescence and old age). Educational psychology largely seeks to apply much of this knowledge and understand how learning can best take place in educational situations. Because of this, the work of child psychologists such as Lev Vygotsky, Jean Piaget and Jerome Bruner has been influential in creating teaching methods and educational practices.

Forensic psychology

Forensic psychology is concerned with the application of psychological methods and principles to legal questions and issues. Most typically, this involves a clinical analysis of a particular individual and an assessment of some specific psycho-legal question.

In the civil law arena, forensic psychologists often provide assessments of whether or not someone has been harmed by some event. For example, in a wrongful death suit, a psychologist might offer opinions as to whether or not a plaintiff suffered emotional trauma in response to the death of a loved one. They might also assess the emotional injuries suffered by someone who has been injured in an accident or who witnessed a traumatic event. Psychologists are often called upon in sexual harassment suits to describe the impact of the harassment on the purported victim. In this arena, the forensic psychologist might be required to provide treatment recommendations or to analyze the specific treatment needs of an individual, and might be asked to determine the potential cost of such treatment.

In the arena of workers' compensation law, a forensic psychologist might be called upon to describe how workplace stress factors impacted the psychological functioning of a claimant, or to determine whether or not the purported work place stress had any affect on the worker at all. As in the more general civil law context, the forensic psychologist might be asked to determine treatment needs and treatment plans.

In the family law arena, forensic psychologists are often called upon to assess the "best interests" of children whose parents are divorcing. Commonly, this involves making recommendations to a Court with respect to child custody arrangements. Child custody mediation is another role that forensic psychologists undertake in the family law arena - serving as a mediator between divorced parents who remain in dispute about the needs and interests of their children. In some jurisdictions, forensic psychologists are appointed as "special masters" by the Court, and are charged with making both recommendations and orders for the care of children in disputed custody situations.

Forensic psychologsists are perhaps most commonly recognized for their involvement in the criminal law. Psychologists provide Courts with analysis relevant to questions of criminal insanity and trial competence. They help Courts decide whether or not sex offenders are likely to re-offend or whether or not they are dangerous. They provide information and recommendations necessary for sentencing purposes, grants of probation, and the formulation of conditions of parole. Forensic psychologists are routinely called upon in death penalty cases to provide analysis of the intentions, motivations and personality characteristics of the accused. In the Juvenile Courts, they often are asked to help determine whether or not a youthful offender can be rehabilitated. They assist prosecutors, defenders, and law enforcement investigators in understanding a range of normal and criminal behaviors, sometimes serving as "criminal profilers."

Forensic psychology refers to any application of psychological principles, methods or understanding to legal questions or issues.

In addition to the applied practices, it also includes academic or empircal research on topics involving law and human behavior.

Health psychology

Whereas clinical psychology focuses on mental health and neurological illness, health psychology is concerned with the psychology of a much wider range of health-related behaviour including healthy eating, the doctor-patient relationship, a patient's understanding of health information, and beliefs about illness. Health psychologists may be involved in public health campaigns, examining the impact of illness or health policy on quality of life or in research into the psychological impact of health and social care.

Industrial and organizational psychology

Involved with the application of psychology to the world of business, commerce and the function of organizations, industrial and organisational psychology focuses to varying degrees on the psychology of the workforce, customer, and consumer, including issues such as the psychology of recruitment, selecting employees from an applicant pool which overall includes training, performance appraisal, job satisfaction, work behaviour, stress at work and management.


Neuropsychology is a branch of psychology that aims to understand how the structure and function of the brain relates to specific psychological processes. Often neuropsychologists are employed as scientists to advance scientific or medical knowledge. Cognitive neuropsychology is particularly concerned with the understanding of brain injury in an attempt to work out normal psychological function. Clinical neuropsychology is the application of neuropsychology for the clinical management of patients with neurocognitive deficits.

Social psychology

Social psychology aims to understand how we make sense of social situations. For example, this could involve the influence of others on an individual's behaviour (e.g., conformity or persuasion), the perception and understanding of social cues, or the formation of attitudes or stereotypes about other people. Social cognition is a common approach and involves a mostly cognitive and scientific approach to understanding social behaviour.

Topics in psychology

Although in principle, psychology aims to explain all aspects of thought and behaviour, some topics have generated particular interest, either due to their perceived importance, their ease of study or popularity. Many of the concepts studied by professional psychology stem from the day-to-day psychology used by most people and learnt through experience. This is known as folk psychology to distinguish it from psychological knowledge developed through formal study and investigation. The extent to which folk psychology should be used as a basis for understanding human experience is controversial, although theories that are based on everyday notions of the mind have been among some of the most successful.

Comprehensive list of psychological topics

  • Addiction
  • Anti-social behaviour
  • Attention
  • Attitude
  • Brain and nervous system function
  • Brain injury
  • Child development
  • Cognition
  • Communication
  • Conditioning
  • Conformity
  • Consciousness
  • Crime
  • Decision making
  • Emotion
  • Ergonomics
  • Executive function
  • Experimental analysis of behavior
  • Face perception
  • Group dynamics
  • Human computer interaction
  • Language and language acquisition
  • Learning
  • Memory
  • Mental illness
  • Motivation
  • Perception
  • Personality
  • Problem solving
  • Program evaluation
  • Psychological testing
  • Psychopathology
  • Psychopharmacology
  • Psychotherapy
  • Reasoning and decision making
  • Rehabilitation
  • Reinforcement
  • Research methods
  • Sensory experience
  • Sexuality and gender role
  • Social cognition
  • Social influence
  • Vision

Divisions and approaches in psychology

Different disciplines in psychology typically signify both a set of practices and an area of interest. The divisions are largely arbitrary and overlapping (although they may have been formalised into areas of interest by psychological societies or regulatory bodies) and most psychologists will use methods from each area as appropriate, even if they mostly focus on one area of interest in their work.

  • Abnormal psychology
  • Activity theory
  • Analytical psychology
  • Applied psychology
  • Asian Psychology
  • Behavior analysis
  • Behavioural medicine
  • Behavioural psychology
  • Biobehavioural health
  • Biological psychology
  • Biopsychology
  • Cognitive neuropsychology
  • Cognitive psychology
  • Cognitive neuroscience
  • Community psychology
  • Comparative psychology
  • Clinical psychology
  • Counselling psychology
  • Critical psychology
  • Developmental psychology
  • Discursive psychology
  • Distributed cognition
  • Dynamic cognition
  • Ecological psychology
  • Educational psychology
  • Embodied cognition
  • Emotional clearing
  • Engineering psychology
  • Evolutionary psychology
  • Experimental psychology
  • Forensic psychology
  • Health psychology
  • Humanistic psychology
  • Individual differences psychology
  • Industrial and organizational psychology
  • Medical psychology
  • Music psychology
  • Neuropsychology
  • Performance psychology
  • Personality psychology
  • Philippine Psychology
  • Physiological psychology
  • Popular psychology, self-help, and alternative therapy
  • Political psychology
  • Positive psychology
  • Pre- and perinatal psychology
  • Problem solving
  • Psychoanalysis
  • Psychohistory
  • Psychology of religion
  • Psychometrics
  • Psychonomics
  • Psychophysics
  • Psychophysiology
  • Psychotherapy a branch of psychiatry as well
  • School psychologist
  • Sensation and Perception
  • Situated cognition
  • Social psychology
  • Sport Psychology
  • Systemic psychology
  • Theoretical psychology
  • Traffic psychology
  • Transpersonal psychology

Some related disciplines

  • Artificial consciousness (see also simulated consciousness)
  • Cognitive science
  • Complex systems
  • Computer science and captology
  • Counseling
  • Discourse analysis
  • Economics and marketing
  • Education
  • Ethology
  • Game theory
  • History
  • Hypnotherapy
  • Linguistics and especially psycholinguistics
  • Literature, literary theory, and critical theory
  • Neuroeconomics
  • Neuro-linguistic programming
  • Neuroscience
  • Philosophy of mind
  • Philosophy of psychology
  • Psycholinguistics
  • Psychology of religion
  • Psychometrics
  • Psychophysics
  • Sociology
  • Socionics
  • Systems theory