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A disease of the nervous system characterized by a progressive dementia that leads to profound impairment in cognition and behavior. Dementia occurs in a number of brain diseases where the impairment in cognitive abilities represents a decline from…

A psychiatric disorder in which a dramatic reduction in caloric intake consequent to excessive dieting leads to significant bodily, physiological, biochemical, emotional, psychological, and behavioral disturbances. Anorexia nervosa is one of three…

A group of distinct psychiatric disorders including generalized anxiety disorder, panic disorder, obsessive-compulsive disorder, social anxiety disorder, specific phobia, and posttraumatic stress disorder. Whereas fear is an adaptive emotion that is…

A neurodevelopmental condition that impairs the way that a person relates to and communicates with other people. Persons with autism have difficulties with social communication and interaction. They also can have unusual behaviors, such as…

Unwanted, aggressive behavior that involves a real or perceived power inequity. The behavior of bullying is often chronic and includes actions such as threats, spreading rumors, attacking someone physically or verbally, and purposefully excluding or…

The visual perception of different wavelengths of light. Light can be understood both as electromagnetic waves and as particles called photons. Photons can have different energies. The energy of a photon determines the frequency and wavelength of…

A form of cognitive-behavioral therapy. Dialectical behavior therapy (DBT) is a psychotherapy developed by psychologist Marsha M. Linehan in the 1990s and designed originally to treat borderline personality disorder (BPD). DBT derives from a…

Those organ systems of the animal body which mediate overt behavior. Injury to an effector system leads to loss or to subnormal execution of behavior patterns mediated by the system, conditions termed paralysis and paresis, respectively.Overt…

Application of the theories, constructs, and analytical methods of linguistics to questions that arise in civil, criminal, and security investigations and adjudication. Understanding linguistics as a social science is essential, because almost all…

The human brain is a bilaterally symmetrical structure which is for the most part richly interconnected by two main bridges of neurons called the corpus callosum and anterior commissure. These structures can be surgically sectioned in humans in an…

A term most commonly used to refer to the subjective feelings that accompany the need for food. Hunger is the craving or desire for food. In addition, the study of the topic of hunger has come to include consideration of the overall control of food…

A relatively complex response pattern that is usually present in one or both sexes of a given animal species. Instinctive behavior (see illustration) comprises any species-typical pattern of responses that are not clearly acquired through training.…

A developmental disorder characterized by significantly subaverage general intellectual functioning, with concurrent, significant deficits in adaptive behavior. Intellectual disability, formerly termed mental retardation, is a condition in which the…

An instrumental device that in theory could detect an involuntary physiological response that all persons exhibit when lying but never when telling the truth. Lie detector tests rely on polygraphic recordings of palmar sweating, respiration, and…

The science of language. Linguistics, that is, the scientific study of language, is concerned with the general and universal properties of language. Interest in language seems to have arisen in the earliest history of the human species. Every…

The perceptual intensity of sound. Loudness depends importantly on the physical intensity of sound, increasing when physical intensity increases and decreasing when physical intensity decreases. But loudness also depends on other physical properties…

Interference with the audibility of a sound caused by the presence of another sound. More specifically, the number of decibels (dB) by which the intensity level of a sound (signal) must be raised above its threshold of audibility, to be heard in the…

The mental ability to store and access information that has been acquired through experience. Memory (Fig. 1) is a critical component of practically all aspects of human thinking, including perception, learning, language, and problem solving.…

Clusters of emotional, cognitive, and/or behavioral symptoms in an individual reflecting an underlying psychobiological disturbance of sufficient severity to cause clinically significant distress or impairment in social or occupational functioning.…

Any of a number of procedures for the fitting of a selected geometric model to a body of multivariate data. In the original form advanced by Warren S. Torgerson, multidimensional scaling dealt with judgments about stimuli, with its major aim being…

An integrative field of research that analyzes brain activity while experimental subjects make decisions. Neuroeconomics is a consilient discipline (that is, a discipline that combines the principles of other disciplines to produce a comprehensive…

One of the chemical senses, specifically the sense of smell. Olfaction comprises the action or capacity of smelling, and is a form of chemoreception (the ability of organisms to detect changes in the chemical composition of their exterior or…

All of the psychological interactions between humans (and animals) and the world of sound. It encompasses all studies of the perception of sound, as well as the production of speech. Hearing The simplest sounds—that is, pure sine waves—can be…

An area of study which draws from linguistics and psychology and focuses upon the comprehension and production of language in its spoken, written, and signed forms. Although psychologists have long been interested in language, and the field of…

Any disorder of higher mental processes of such severity that judgments pertaining to the reality of external events are significantly impaired. Psychosis, or psychotic disorder, is a defective mental state in which there is a critical derangement…

A simple, unlearned, yet specific behavioral response to a specific stimulus. A reflex is an involuntary response or reaction to a particular stimulus (Fig. 1). Reflexes are exhibited by virtually all animals from protozoa to primates. Along with…

Sequences of deoxyribonucleic acid (DNA) that increase the probability of the development of schizophrenia in an individual. Schizophrenia risk genes increase the likelihood of developing schizophrenia, a debilitating brain disorder characterized by…

Disorders or disturbances of the reversible state during which an individual's voluntary functions are suspended, but the involuntary functions (such as circulation and respiration) are uninterrupted. Sleep is a state of rest in which consciousness…

Problems of speech production, articulation, or voice, or disruptions of the ability to use language. Speech disorders can be categorized in a variety of ways, but most belong to one of the following types: articulation, voice, fluency, and…

The totality of the perceptual processes necessary to distinguish, recognize, and interpret speech sounds. In the broadest sense, speech perception refers to how an individual hears and understands what others are saying (Fig. 1). More narrowly,…

A general term used to describe environmental events of a challenging sort as well as the body's response to such events, in which a sense of control and ability to cope is an important factor in determining responses. In a general biological sense,…

A death that is self-inflicted and carried out with intent to die; also, one who completes such an act. Suicide is a serious epidemiological public health problem that devastates individuals, families, and communities throughout the world. There are…

A pattern of behavior in which an animal actively defends a space or some other resource. Territoriality is an important aspect of the behavior of many animals (see illustration). It is observed throughout the animal kingdom and is particularly…

A type of cell receptor in taste buds that detects the savory taste quality known as umami. Umami is one of the five basic taste qualities that humans can detect, along with sweet, bitter, salty, and sour. It was discovered in 1908 by Kikunae Ikeda,…

Habituation to a specific practice, such as drinking alcoholic beverages or using drugs (for example, heroin, cocaine, or amphetamines), and disorders characterized by the chronic use of a drug, alcohol, or similar substance. Addiction and addictive…

Behavior that is intended to threaten or inflict physical injury or emotional harm on another person or organism. Aggression is a type of behavior (physical or verbal, or both) displayed by an individual who aims or is motivated to harm another…

Any disorder of recognition. Agnosias were named originally by Sigmund Freud in 1891 to denote disturbances in the ability to recognize and name objects. Usually the misrecognition involves one sensory modality, with primary sensation in that…

The repeated and/or excessive use of alcohol (ethanol) that continues despite negative physical, psychiatric, or social consequences. Alcoholism is characterized by consuming alcohol more often, in larger amounts, or over longer periods than…

A significant but relatively selective inability to remember. Amnesia can be characterized along two dimensions with respect to its onset: an inability to remember events that occurred after the onset of amnesia is referred to as anterograde…

A disorder of language, acquired as a result of brain disease. Aphasia strikes at that most human of attributes—communication with other people. Aphasia must be distinguished from three other conditions: motor speech disorders, developmental…

An impairment in the performance of voluntary actions despite intact motor power and coordination, sensation and perception, and comprehension. The apraxic person knows the act to be carried out, and has the requisite sensory-motor capacities; yet…

A common psychiatric disorder (especially in children) characterized by attentional difficulties, impulsivity, and hyperactivity. Attention deficit hyperactivity disorder (ADHD) is a mental disorder marked by an individual's inability to pay…

The quantitative assessment of individual hearing, both normal and defective. In typical tests, pure tones are presented through headphones, though some tests use speech instead of tones. In bone conduction tests, tones are presented through a…

The branch of ecology that focuses on the evolutionary causes of variation in behavior among populations and species. The scientific study of behavioral ecology investigates how changes of behavior are influenced by ecological factors (Fig. 1).…

A major mental disorder in which there are lifelong episodes of both mania and depression; also known as manic-depressive illness. Bipolar disorder, also termed manic-depressive illness or manic depression, is characterized by sudden and often…

The internal structures and processes that are involved in the acquisition and use of knowledge, including sensation, perception, attention, learning, memory, language, thinking, and reasoning. The mental processes and behaviors that constitute…

Technology used to augment human mental capacity. In contrast, technology is widely used to augment human physical capabilities. We can move faster using cars, we can lift heavier weights using cranes, and we can even fly through the air using…

A psychotherapy with roots in both cognitive science and behavioral science. Cognitive-behavioral therapy (CBT) is the most widely used evidence-based psychotherapeutic practice for a variety of mental health disorders, including anxiety, depression…

The ability to discriminate light on the basis of wavelength composition. Color vision is found in humans, in other primates, and in certain species of birds, fishes, reptiles, crustaceans, and insects. These animals have visual receptors that…