The De anima of Aristotle is considered the first monument of psychology as such, centered around the belief that the heart was the basis for mental activity. The foundations of modern psychology were laid by 17th-century philosopher Thomas Hobbes, who argued that scientific causes could be established for every sort of phenomenon through deductive reasoning. The mind-body theories of Rene Descartes, Baruch Spinoza, and G. W. Leibniz were equally crucial in the development of modern psychology, where the human mind's relation to the body and its actions have been significant topics of debate.
In England the empirical method employed in modern psychological study originated in the work of John Locke, George Berkeley, Thomas Reid, and David Hume. David Hartley, James Mill, John Stuart Mill, and Alexander Bain stressed the relation of physiology to psychology, an important development in the scientific techniques of modern psychology. Important contributions were made in the physiological understanding of human psychology by French philosopher Condillac, F. J. Gall, the German founder of phrenology, and French surgeon Paul Broca, who localized speech centers in the brain.
In the 19th cent., the laboratory work of Ernst Heinrich Weber, Gustave Fechner, Wilhelm Wundt, Hermann von Helmholtz, and Edward Titchener helped to establish psychology as a scientific discipline—both through the use of the scientific method of research, and in the belief that mental processes could be quantified with careful research techniques. The principle of evolution, stemming from Charles Darwin's theory of natural selection, gave rise to what became known as dynamic psychology. The new approach, presented by American psychologist William James in his Principles of Psychology (1890), looked at consciousness as an evolutionary process.
Out of the new orientation in psychology grew the clinical experiments in hysteria and hypnotism carried on by J. M. Charcot and Pierre Janet in France. Sigmund Freud, in his influential theory of the unconscious, gave a new direction to psychology and laid the groundwork for the psychoanalytic model. Freudian theory took psychology into such fields as education, anthropology, and medicine, and Freudian research methods became the foundations of clinical psychology.
The behaviorism of American psychologist John B. Watson was highly influential in the 1920s and 30s, with its suggestion that psychology should concern itself solely with sensory stimuli and behavioral reaction. Behaviorism has been important in modern psychology, particularly through the work of B. F. Skinner since the 1930s.
Equally important was the development of Gestalt psychology by German psychologists Kurt Koffka, Wolfgang Köhler, and Max Wertheimer. Gestalt theory contended that the task of psychology was to study human thought and behavior as a whole, rather than breaking it down into isolated instances of stimulus and response.
Another influential school of psychology was developed in the 1950s and 60s by Abraham Maslow and Carl Rogers. Their humanistic theory asserts that people make rational, conscious decisions regarding their lives, and optimistically suggests that individuals tend to reach toward their greatest potential.
Modern psychology is divided into several subdisciplines, each based on differing models of behavior and mental processes. Psychologists work in a number of different settings, including universities and colleges, primary and secondary schools, government agencies, private industry, hospitals, clinics, and private practices. Recent years have seen a rise in the significance of applied psychology—as can be seen from the areas contemporary psychologists concern themselves with—with an attendant decline in the importance of psychology in academia. In the United States, clinical psychology has become a significant focus of the discipline, largely separate from psychological research. Clinical psychologists are responsible for the diagnosis and treatment of various psychological problems.
Biological models of behavior have become increasingly prominent in psychological theory, particularly with the development of various tools—such as the positron emission tomography (PET) scan—for mapping the brain. The field of neuropsychology, which studies the brain and the connected nervous system, has been an outgrowth of this contemporary focus on biological explanations of human thought and behavior. Cognitive models, derived from the Gestalt school of psychology, focus on the various thinking processes which mediate between stimuli and responses.
Educational psychology, derived from the 18th and 19th cent. educational reforms of Friedrich W. Froebel, Johann Pestalozzi, and their follower Johann Herbart, was later expanded by G. Stanley Hall and by E. L. Thorndike. It is concerned with the development of improved methods of teaching and learning.
Social psychology, developed by British psychologists William McDougall and Havelock Ellis, studies the effects of various social environments on the individual. Some other branches of the field include developmental psychology, which studies the changes in thought and behavior through the course of life; experimental psychology, which is the laboratory research involved in the understanding of the mind; and personality psychology, which deals specifically with individual personality and the processes by which it is formed.
In recent years a number of new fields of psychology have emerged. Industrial/organizational psychology, emerging from social psychology, focuses on the workplace and considers such topics as job satisfaction, leadership, and productivity. Health psychology examines how psychological factors contribute to pathology, and demonstrates how psychology can contribute to recovery and illness prevention for such somatic disorders as heart disease, cancer, and diabetes. In environmental psychology, research focuses on how individuals react to their physical environments, and suggests improvements which may be beneficial to psychological health. Other new areas of psychology include counseling psychology, school psychology, forensic psychology, and community psychology.
See R. Fancher, Pioneers in Psychology (1979); D. Robinson, An Intellectual History of Modern Psychology (1986); E. Hilgard, Psychology in America (1987); M. Ash and W. Woodward, Psychology in 20th Century Thought and Society (1989); R. B. Evans, V. S. Sexton, and T. C. Cadwallader, ed., The American Psychological Association (1992).
Branch of psychology concerned with the personality, attitudes, motivations, and behaviour of the individual or group in the context of social interaction. The field emerged in the U.S. in the 1920s. Topics include the attribution of social status based on perceptual cues, the influence of social factors (such as peers) on a person's attitudes and beliefs, the functioning of small groups and large organizations, and the dynamics of face-to-face interactions.
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Study of the physiological basis of behaviour. Traditional specializations in the field cover perception, motivation, emotion, learning, memory, cognition, or mental disorders. Also considered are other physical factors that affect the nervous system, including heredity, metabolism, hormones, disease, drug ingestion, and diet. An experimental science, physiological psychology relies heavily on laboratory research and quantitative data.
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Application of the concepts and methods of experimental, clinical, and social psychology to the workplace. I-O psychologists are concerned with such matters as personnel evaluation and placement, job analysis, worker-management relations (including morale and job satisfaction), workforce training and development (including leadership training), and productivity improvement. They may work closely with business managers, industrial engineers, and human-resources professionals.
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Twentieth-century movement in psychology, developed largely in reaction against behaviourism and psychoanalysis, that emphasizes the importance of values, intentions, and meaning in the compass of the individual. The concept of the “self” is a central focus for most humanistic psychologists. Architects of the humanistic approach included Abraham H. Maslow, Carl R. Rogers, and Rollo May (1909–94). Types of humanistic therapies have included sensory awareness, encounter groups, existential analysis, Gestalt therapy, logotherapy, and various transpersonal, human-potential, holistic-health, and addiction-recovery schools.
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In psychology, a broad school of thought that originated in the U.S. in the late 19th century and emphasized the total organism in its endeavours to adjust to the environment. Reacting against the school of structuralism led by Edward Bradford Titchener, functionalists such as William James, George Herbert Mead, and John Dewey stressed the importance of empirical, rational thought over an experimental trial-and-error philosophy. The movement concerned itself primarily with the practical applications of research (see applied psychology) and was critical of early forms of behaviourism.
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Branch or type of psychology concerned with employing empirical principles and procedures in the study of psychological phenomena. The experimental psychologist seeks to carry out tests under controlled conditions in order to discover an unknown effect or law, to examine or establish a hypothesis, or to illustrate a known law. The areas of study that rely most heavily on the experimental method include those of sensation and perception, learning and memory, motivation, and physiological psychology. Experimental approaches are also used in child psychology, clinical psychology, educational psychology, and social psychology.
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Profession of designing machines, tools, and work environments to best accommodate human performance and behaviour. It aims to improve the practicality, efficiency, and safety of a person working with a single machine or device (e.g., using a telephone, driving a car, or operating a computer terminal). Taking the user into consideration has probably always been a part of tool design; for example, the scythe, one of the oldest and most efficient human implements, shows a remarkable degree of ergonomic engineering. Examples of common devices that are poorly designed ergonomically include the snow shovel and the computer or typewriter keyboard.
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Branch of psychology concerned with the learning processes and psychological issues associated with the teaching and training of students. The educational psychologist studies the cognitive development of students and the various factors involved in learning, including aptitude and learning measurement, the creative process, and the motivational forces that influence student-teacher dynamics. Two early leaders in the field were G. Stanley Hall and Edward L. Thorndike. Seealso school psychology.
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Branch of psychology concerned with changes in cognitive, motivational, psychophysiological, and social functioning that occur throughout the human life span. In the late 19th and early 20th centuries, developmental psychologists were concerned primarily with child psychology. In the 1950s they became interested in the relationship between child rearing and adult personality, as well as in examining adolescence in its own right. By the late 20th century they had become interested in all aspects of psychological development and change over the entire life span.
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Study of similarities and differences in behavioral organization among living beings. The discipline pays particular attention to the psychological nature of humans in comparison with other animals. It began to emerge in the late 19th century and grew rapidly in the 20th century, involving experimental studies on human and animal brain function, learning, and motivation. Well-known studies have included those of Ivan Pavlov on conditioning in laboratory dogs, those of Harry Harlow (1905–81) on the effects of social deprivation in monkeys, and those of various researchers on language abilities in apes.
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Branch of psychology concerned with the diagnosis and treatment of mental disorders. Clinical psychologists evaluate patients through interviews, observation, and psychological tests, and they apply current research findings and methodologies in making diagnoses and assigning treatments. Most clinical psychologists hold an academic degree (Ph.D. or Psy.D.) rather than a medical degree (M.D.); they may provide psychotherapy but cannot prescribe medications. Most practictioners work in hospitals or clinics or in private practice, often in tandem with psychiatrists and social workers, treating mentally or physically disabled patients, prison inmates, drug and alcohol abusers, and geriatric patients, among others. Seealso psychiatry; social work.
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Study of the psychological processes of children. The field is sometimes subsumed under developmental psychology. Data are gathered through observation, interviews, tests, and experimental methods. Principal topics include language acquisition and development, motor skills, personality development, and social, emotional, and intellectual growth. The field began to emerge in the late 19th century through the work of German psychophysiologist William Preyer, American psychologist G. Stanley Hall, and others. In the 20th century the psychoanalysts Anna Freud and Melanie Klein devoted themselves to child psychology, but its most influential figure was Jean Piaget, who described the various stages of childhood learning and characterized children's perceptions of themselves and the world at each stage. Seealso school psychology.
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Branch of psychology concerned with solving practical problems of human behaviour by using the findings and methods of psychological science. Intelligence testing, legal problems, industrial efficiency, motivation, and delinquency were among the first areas of application in the early 20th century. World Wars I and II fostered work on vocational testing, teaching methods, evaluation of attitudes and morale, performance under stress, propaganda and psychological warfare, and rehabilitation. The aviation and aerospace industries were important for the development of engineering psychology, the study of human-machine relationships. Other areas include consumer psychology, school psychology, and community psychology. Seealso industrial-organizational psychology; psychometrics.
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Psychoanalytic method of Carl Jung as he distinguished it from that of Sigmund Freud. Jung attached less importance than did Freud to the role of childhood sexual conflicts in the development of neurosis. Moreover, he defined the unconscious to include both the individual's own unconscious and that inherited, partly in the form of archetypes, from his or her ancestors (the “collective unconscious”). He classified people into introvert and extravert types and further distinguished them according to four primary functions of the mind—thinking, feeling, sensation, and intuition—one or more of which predominated in any given person.
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Branch of psychology. It is concerned with mental and emotional disorders (e.g., neurosis, psychosis, mental deficiency) and with certain incompletely understood normal phenomena (such as dreams and hypnosis). The chief tool used in classifying psychological disorders is the American Psychiatric Assn.'s Diagnostic and Statistical Manual of Mental Disorders 4th edition (DSM-IV).
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Psychology (from Greek ψῡχή, psȳkhē, "breath, life, soul"; and -λογία, -logia) is an academic and applied discipline involving the scientific study of mental processes and behavior. Psychologists study such phenomena as perception, cognition, emotion, personality, behavior, and interpersonal relationships. Psychology also refers to the application of such knowledge to various spheres of human activity, including issues related to everyday life (e.g. family, education, and employment) and the treatment of mental health problems. Psychologists attempt to understand the role of these functions in individual and social behavior, while also exploring the underlying physiological and neurological processes. Psychology includes many sub-fields of study and application concerned with such areas as human development, sports, health, industry, media, and law.
Though the use of psychological experimentation dates back to Alhazen's Book of Optics in 1021, psychology as an independent experimental field of study began in 1879, when Wilhelm Wundt founded the first laboratory dedicated exclusively to psychological research at Leipzig University in Germany, for which Wundt is known as the "father of psychology". 1879 is thus sometimes regarded as the "birthdate" of psychology. The American philosopher William James published his seminal book, Principles of Psychology, in 1890, while laying the foundations for many of the questions that psychologists would focus on for years to come. Other important early contributors to the field include Hermann Ebbinghaus (1850–1909), a pioneer in the experimental study of memory at the University of Berlin; and the Russian physiologist Ivan Pavlov (1849-1936), who investigated the learning process now referred to as classical conditioning.
During the 1890s, the Austrian physician Sigmund Freud developed a method of psychotherapy known as psychoanalysis. Freud's understanding of the mind was largely based on interpretive methods, introspection and clinical observations, and was focused in particular on resolving unconscious conflict, mental distress and psychopathology. Freud's theories became very well-known, largely because they tackled subjects such as sexuality, repression, and the unconscious mind as general aspects of psychological development. These were largely considered taboo subjects at the time, and Freud provided a catalyst for them to be openly discussed in polite society. Freud also had a significant influence on Carl Jung, whose analytical psychology became an alternative form of depth psychology. Philosopher Karl Popper argued that Freud's psychoanalytic theories were presented in untestable form. Due to their subjective nature, Freud's theories are often of limited interest to many scientifically-oriented psychology departments. Followers of Freud who accept the basic ideas of psychoanalysis but alter it in some way are called neo-Freudians. Modification of Jung's theories has led to the archetypal and process-oriented schools of psychological thought.
Behaviorism differs from other perspectives in a number of ways. Behaviorists focus on behavior-environment relations and analyze overt and covert (i.e., private) behavior as a function of the organism interacting with its environment . Behaviorists do not reject the study of covert or private events (e.g., dreaming). What behaviorists reject is an autonomous causal entity inside the organism that causes overt (e.g., walking, talking) or covert (e.g., dreaming, imagining) behavior. Concepts such as "mind" or "consciousness" are not used by behaviorists because such terms do not describe actual psychological events (such as imagining) but are used as explanatory entities hidden somewhere in the organism. By contrast, behavorism treats private events as behavior, and analyzes them in the same way as overt behavior (hence the name "behaviorism"). Behavior refers to the concrete events of the organism, overt or private. Furthermore, the focus on behavior-environment relations does not neglect the importance of genes or biology in relation to behavior. Rather, the study of behavior-environment relations provides a powerful tool to examine the effects of these and other variables. Skinner was also a proponent of introspection in the sense that he felt it could be used to point to environmental variables of which behavior (overt and covert) is a function (Skinner, 1974). To Skinner, however, what was "spected" in introspection was not mental phenomena, but the organisms physical body. Other behaviorists before Skinner had differing views regarding these matters. For instance, in "Psychology as the Behaviorist Views It" (1913), Watson argued that psychology "is a purely objective experimental branch of natural science," that "introspection forms no essential part of its methods," and that "the behaviorist recognizes no dividing line between man and brute." Skinner rejected hypothesis testing as a research method, considering it to be too conducive to speculative theories that may desensitize the researcher to interesting and unanticipated happenings in his experiments.
Behaviorism was the dominant paradigm in American psychology throughout the first half of the 20th century. However, the modern field of psychology is largely dominated by cognitive psychology. Linguist Noam Chomsky's 1959 review of B. F. Skinner's Verbal Behavior challenged the behaviorist approaches to studies of behavior and language dominant at the time and contributed to the cognitive revolution in psychology. Chomsky was highly critical of what he considered arbitrary notions of 'stimulus', 'response' and 'reinforcement' which Skinner borrowed from animal experiments in the laboratory. Chomsky argued that Skinner's notions could only be applied to complex human behavior, such as language acquisition, in a vague and superficial manner. Chomsky emphasized that research and analysis must not ignore the contribution of the child in the acquisition of language and proposed that humans are born with a natural ability to acquire language. Work most associated with psychologist Albert Bandura, who initiated and studied social learning theory, showed that children could learn aggression from a role model through observational learning, without any change in overt behavior, and so must be accounted for by internal processes.
Links between brain and nervous system function also became understood, partly due to the experimental work of people such as Charles Sherrington and Donald Hebb, and partly due to studies of people with brain injury (see cognitive neuropsychology). With the development of technologies for measuring brain function, neuropsychology and cognitive neuroscience have become increasingly active areas of contemporary psychology. Cognitive psychology has been subsumed along with other disciplines, such as philosophy of mind, computer science, and neuroscience, under the umbrella discipline of cognitive science.
In modern times, psychology has adopted an integrated perspective towards understanding consciousness, behavior, and social interaction. This perspective is commonly referred to as the biopsychosocial approach. The basic tenet of the biopsychosocial model is that any given behavior or mental process affect and are affected by dynamically interrelated biological, psychological, and social factors.
The psychological aspect refers to the role that cognition and emotions play in any given psychological phenomenon. For example, the effect of mood or beliefs and expectations on an individual's reactions to an event. The biological aspect refers to the role that biological factors (such as genetic variability or brain function and development) play in a psychological phenomenon. For example, the effect that the prenatal environment and brain development may have on an individual's future cognitive ability. The socio-cultural aspect refers to the role that social and cultural environments play in a given psychological phenomenon. For example, the role of parental or peer influence in the behaviors or characteristics of an individual.
In the study of abnormal behavior, it can be difficult to define the line between which behaviors are considered normal and which are not. In general, abnormal behaviors must be maladaptive and cause an individual subjective discomfort (signs of emotional distress). Generally, abnormal behaviors are classified as:
Biological psychology is the scientific study of the biological bases of behavior and mental states. Because all behavior is controlled by the nervous system, it is sensible to study how the brain functions in order to understand behavior. This is the approach taken in behavioral neuroscience, cognitive neuroscience, and neuropsychology. Neuropsychology is the branch of psychology that aims to understand how the structure and function of the 'brain' relate to specific behavioral and psychological processes. Often neuropsychologists are employed as scientists to advance scientific or medical knowledge. Neuropsychology is particularly concerned with the understanding of brain injury in an attempt to work out normal psychological function. The approach of cognitive neuroscience to studying the link between brain and behavior is to use neuroimaging tools, such as to observe which areas of the brain are active during a particular task.
Cognitive psychology studies cognition, the mental processes underlying behavior. It uses information processing as a framework for understanding the mind. Perception, learning, problem solving, memory, attention, language and emotion are all well researched areas. Cognitive psychology is associated with a school of thought known as cognitivism, whose adherents argue for an information processing model of mental function, informed by positivism and experimental psychology.
On a broader level, Cognitive science is a conjoined enterprise of cognitive psychologists, neurobiologists, workers in artificial intelligence, logicians, linguists, and social scientists, and places a slightly greater emphasis on computational theory and formalization. Both areas can use computational models to simulate phenomena of interest. Because mental events cannot directly be observed, computational models provide a tool for studying the functional organization of the mind. Such models give cognitive psychologists a way to study the "software" of mental processes independent of the "hardware" it runs on, be it the brain or a computer.
Comparative psychology refers to the study of the behavior and mental life of animals other than human beings. It is related to disciplines outside of psychology that study animal behavior, such as ethology. Although the field of psychology is primarily concerned with humans, the behavior and mental processes of animals is also an important part of psychological research, either as a subject in its own right (e.g., animal cognition and ethology), or with strong emphasis about evolutionary links, and somewhat more controversially, as a way of gaining an insight into human psychology by means of comparison or via animal models of emotional and behavior systems as seen in neuroscience of psychology (e.g., affective neuroscience and social neuroscience).
The work performed by clinical psychologists tends to be done inside various therapy models, all of which involve a formal relationship between professional and client—usually an individual, couple, family, or small group—that employs a set of procedures intended to form a therapeutic alliance, explore the nature of psychological problems, and encourage new ways of thinking, feeling, or behaving. The four major perspectives are Psychodynamic, Cognitive Behavioral, Existential-Humanistic, and Systems or Family therapy. There has been a growing movement to integrate these various therapeutic approaches, especially with an increased understanding of issues regarding culture, gender, spirituality, and sexual-orientation. With the advent of more robust research findings regarding psychotherapy, there is growing evidence that most of the major therapies are about of equal effectiveness, with the key common element being a strong therapeutic alliance. Because of this, more training programs and psychologists are now adopting an eclectic therapeutic orientation.
Mainly 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 processes change as they age. This may focus on intellectual, cognitive, neural, social, or moral development. Researchers who study children use a number of unique research methods to make observations in natural settings or to engage them in experimental tasks. Such tasks often resemble specially designed games and activities that are both enjoyable for the child and scientifically useful, and researchers have even devised clever methods to study the mental processes of small infants. In addition to studying children, developmental psychologists also study aging and processes throughout the life span, especially at other times of rapid change (such as adolescence and old age). Developmental psychologists draw on the full range of theorists in scientific psychology to inform their research.
Personality psychology studies enduring psychological patterns of behavior, thought and emotion, commonly called an individual's personality. Theories of personality vary between different psychological schools. Trait theories attempts to break personality down into a number of traits, by use of factor analysis. The number of traits have varied between theories. One of the first, and smallest, models was that of Hans Eysenck, which had three dimensions: extroversion—introversion, neuroticism—emotional stability, and psychoticism. Raymond Cattell proposed a theory of 16 personality factors. The theory that has most empirical evidence behind it today may be the "Big Five" theory, proposed by Lewis Goldberg, and others.
Psychology and law (or Legal psychology) is a research-oriented field populated with researchers from several different areas within psychology (although social and cognitive psychologists are typical). Legal psychologists explore such topics as jury decision-making, eyewitness memory, scientific evidence, and legal policy. The term "legal psychology" has only recently come into use, and typically refers to any non-clinical law-related research.
Quantitative psychology involves the application of mathematical and statistical modeling in psychological research, and the development of statistical methods for analyzing and explaining behavioral data. The term Quantitative psychology is relatively new and little used (only recently have Ph.D. programs in quantitative psychology been formed), and it loosely covers the longer standing subfields psychometrics and mathematical psychology.
Psychometrics is the field of psychology concerned with the theory and technique of psychological measurement, which includes the measurement of knowledge, abilities, attitudes, and personality traits. Measurement of these unobservable phenomena is difficult, and much of the research and accumulated knowledge in this discipline has been developed in an attempt to properly define and quantify such phenomena. Psychometric research typically involves two major research tasks, namely: (i) the construction of instruments and procedures for measurement; and (ii) the development and refinement of theoretical approaches to measurement.
Whereas psychometrics is mainly concerned with individual differences and population structure, mathematical psychology is concerned with modeling of mental and motor processes of the average individual. Psychometrics is more associated with educational psychology, personality, and clinical psychology. Mathematical psychology is more closely related to psychonomics/experimental and cognitive, and physiological psychology and (cognitive) neuroscience.
Social psychology is the study of the nature and causes of human social behavior and mental processes, with an emphasis on how people think towards each other and how they relate to each other. Social Psychology aims to understand how we make sense of social situations. For example, social psychologists study the influence of others on an individual's behavior (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 behavior.
Research in experimental psychology is conducted in broad accord with the standards of the scientific method, encompassing both qualitative ethological and quantitative statistical modalities to generate and evaluate explanatory hypotheses with regard to psychological phenomena. Where research ethics and the state of development in a given research domain permits, investigation may be pursued by experimental protocols. Psychology tends to be eclectic, drawing on knowledge from other fields to help explain and understand psychological phenomena. Qualitative psychological research utilizes a broad spectrum of observational methods, including action research, ethography, exploratory statistics, structured interviews, and participant observation, to enable the gathering of rich information unattainable by classical experimentation. Research in humanistic psychology is more typically pursued via ethnographic, historical, and historiographic methods.
The testing of different aspects of psychological function is a significant area of contemporary psychology. Psychometric and statistical methods predominate, including various well-known standardized 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. These approaches are not mutually exclusive, and many psychologists will be involved in both researching and applying psychology at some point during their career. Many clinical psychology programs aim to develop in practicing psychologists both knowledge of and experience with research and experimental methods, which they may interpret and employ as they treat individuals with psychological issues.
When an area of interest requires specific training and specialist knowledge, especially in applied areas, psychological associations normally establish 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.
Experimental psychological research is conducted in a laboratory under controlled conditions. This method of research relies on the application of the scientific method to understand behavior. Experimenters use several types of measurements, including rate of response, reaction time, and various psychometric measurements. Experiments are designed to test specific hypotheses (deductive approach) or evaluate functional relationships (inductive approach). They are important for psychological research because they allow researchers to establish causal relationships between different aspects of behavior and the environment. Importantly, in an experiment, one or more variables of interest are controlled by the experimenter (independent variable) and another variable is measured in response to different conditions (dependent variable). (See also hypothesis testing.) Experiments are one of the primary research methodologies in many areas of psychology, particularly cognitive/psychonomics, mathematical psychology, psychophysiology and biological psychology/cognitive neuroscience.
As an example, suppose an experimenter wanted to answer the following question: does talking on a phone affect one's ability to stop quickly while driving? To answer this, the experimenter would want to show that a subject's stopping time is different when they are talking on a phone versus when they are not. If the experiment is properly conducted in a controlled environment and a difference between the two conditions is found, the experimenter would be able to show a causal relationship between phone use and stopping time. In addition to potential practical benefits, this type of experiment may have important theoretical results, such as helping to explain the processes that underlie attention in humans.
Experiments on humans have been put under some controls; namely informed and voluntary consent. After WWII, the Nuremberg Code was established, because of Nazi abuses of experimental subjects. Later, most countries (and scientific journals) adopted the Declaration of Helsinki. In the US, the NIH established the IRB in 1966. And in 1974, adopted the National Research Act (HR 7724). All of which cover informed consent of human participants in experimental studies. There were a number of influential studies which lead to the establishment of these rules, including the MIT & Fernald School radioisotope studies, the Thalidomide Tragedy, Willowbrook hepatitis study, Milgram's obedience to authority studies.
Research designed to answer questions about the current state of affairs such as the thoughts, feelings and behaviors of individuals is known as descriptive research. One distinction that is made in descriptive research concerns whether it is qualitative or quantitative in orientation. Qualitative research is descriptive research that is focused on observing and describing events as they occur, with the goal of capturing all of the richness of everyday behavior and with the hope of discovering and understanding phenomena that might have been missed if only more cursory examinations have been made.
In the same way Jane Goodall studied the role of chimpanzee social and family life, psychologists conduct similar observational studies in human social, professional and family lives. Sometimes the participants are aware they are being observed and other times it is covert; the participants do not know they are being observed. Ethical guidelines need to be taken into consideration when covert observation is being carried out.
Statistical surveys are used in psychology for measuring attitudes and traits, monitoring changes in mood, or checking the validity of experimental manipulations. Most commonly, psychologists use paper-and-pencil surveys. However, surveys are also conducted over the phone or through e-mail. Increasingly, web-based surveys are being used in research. Similar methodology is also used in applied setting, such as clinical assessment and personnel assessment.
Cognitive neuropsychology and cognitive neuropsychiatry study neurological or mental impairment in an attempt to infer theories of normal mind and brain function. This typically involves looking for differences in patterns of remaining ability (known as 'functional disassociation's') which can give clues as to whether abilities are comprised of smaller functions, or are controlled by a single cognitive mechanism.
In addition, experimental techniques are often used which also apply to studying the neuropsychology of healthy individuals. These include behavioral experiments, brain-scanning or functional neuroimaging - used to examine the activity of the brain during task performance, and techniques such as transcranial magnetic stimulation, which can safely alter the function of small brain areas to investigate their importance in mental operations.
Computational modeling is a tool often used in mathematical psychology and cognitive psychology to simulate a particular behavior using a computer. This method has several advantages. Since modern computers process extremely quickly, many simulations can be run in a short time, allowing for a great deal of statistical power. Modeling also allows psychologists to visualize hypotheses about the functional organization of mental events that couldn't be directly observed in a human.
Several different types of modeling are used to study behavior. Connectionism uses neural networks to simulate the brain. Another method is symbolic modeling, which represents many different mental objects using variables and rules. Other types of modeling include dynamic systems and stochastic modeling.
The validity of probability testing as a research tool has been called into question. There is concern that this statistical method may promote trivial findings as meaningful, especially when large samples are used. Some psychologists have responded with an increased use of effect size statistics, rather than sole reliance on the traditional p<.05 decision rule in statistical hypothesis testing.
In recent years, and particularly in the U.S., there has been increasing debate about the nature of therapeutic effectiveness and about the relevance of empirically examining psychotherapeutic strategies. One argument states that some therapies are based on discredited theories and are unsupported by empirical evidence. The other side points to recent research suggesting that all mainstream therapies are of about equal effectiveness, while also arguing that controlled studies often do not take into consideration real-world conditions (e.g. the high co-morbidity rate or the experience of clinicians); that research is heavily biased towards the methods of the cognitive behavioral therapies (CBT); and that it typically under-represents minority groups.