Developmental psychologists study how characteristics and behaviors first appear and how and when they change. They study the relationships between different types of development, such as cognitive and social, as well as individual variations in development, both normal and deviant. Initially, developmental psychology focused on childhood but was subsequently expanded to cover changes that occur o…
Developmental psychologists, by and large, study the way humans develop from an embryo into a full grown adult, focusing mainly on the factors that contribute to intelligence, personality, morality, and lifestyle. Of special interest are the effects certain stimuli have on the development of humans. For instance, does genetics pre-program a person to be introverted, or is that personality trait th…
John Dewey was born near Burlington, Vermont. After receiving his B.A. from the University of Vermont, he taught high school and studied philosophy independently before entering the graduate program in philosophy at Johns Hopkins University. After receiving his Ph.D. in 1884, Dewey served on the faculties of the University of Michigan, the University of Minnesota, the University of Chicago, and Co…
The American Psychiatric Association publishes the Diagnostic and Statistical Manual of Mental Disorders, widely referred to as DSM-IV, a reference work designed to provide guidelines for psychologists and others to use in the diagnosis and classification of mental disorders. The latest edition, DSM-IV, serves as a reference to psychiatrists, other physicians and mental health professionals, psych…
The earliest research in the field of differential psychology began in the late nineteenth century with Francis Galton's investigation of the effects of heredity on individual intelligence and his pioneering work in intelligence testing, which was further advanced by James McKeen Cattell and Alfred Binet. It was Binet who developed the first standardized intelligence test. Growth in related…
In the United States, the term disability is legally defined in the Rehabilitation Act (PL 93-112; 29 U.S.C. 794) Amendments of 1974 and the Americans with Disabilities Act (PL 101-336; 42 U.S.C. 12101) of 1990 as a physical or mental impairment that substantially limits one or more of the major life activities of an individual. Disabilities may be caused by congenital, traumatic, pathological, or…
Dissociation, or the feeling of being detached from the reality of one's body, can be categorized into two types: depersonalization and derealization. Depersonalization is highlighted by a sense of not knowing who you are, or of questioning long-held beliefs about who you are. In derealization, persons perceive reality in a grossly distorted way. Psychologists have identified several types …
Persons suffering from dissociative identity disorder (DID) adopt one or more distinct identities which co-exist within one individual. Each personality is distinct from the other in specific ways. For instance, tone of voice and mannerisms will be distinct, as well as posture, vocabulary, and everything else we normally think of as marking a personality. There are cases in which a person will hav…
The concept of divergent thinking was developed in the 1950s by psychologist J.P. Guilford, who saw it as a major component of creativity and associated it with four main characteristics. The characteristics were fluency (the ability to rapidly produce a large number of ideas or solutions to a problem); flexibility (the capacity to consider a variety of approaches to a problem simultaneously); ori…
The divorce rate in the United States began rising in the 1960s and continued for more than two decades, with a decline in the trend in the 1990s. In 1960 the divorce rate per 1,000 population was 2.6. By 1980, the rate had reached 5.2 and in 1990 dropped to 4.7. This decline continued to 4.3 in 1997. Based on current societal trends, researchers project that 40 to 50 percent of all first marriage…
Down syndrome was named after John Langdon Haydon Down, a British physician and advocate of education for the mentally retarded, who first described it in 1866. In 1959, the French pediatrician Jerome Lejeune discovered that the disorder is caused by a chromosomal abnormality. Ninety-five percent of individuals with Down syndrome have Trisomy 21, an extra chromosome in the 21st pair (altogether, t…
Based on children's drawings of human figures, this test can be used with two different scoring systems for different purposes. One measures nonverbal intelligence while the other screens for emotional or behavioral disorders. During the testing session, which can be completed in 15 minutes, the child is asked to draw three figures—a man, a woman, and him- or herself. To evaluate int…
Dreams defy the laws of physics, the principles of logic, and personal morality, and may reflect fears, frustrations, and personal desires. Often occurring in story-form with the dreamer as participant or observer, dreams usually involve several characters, motion, and may include sensations of taste, smell, hearing, or pain. The content of dreams clearly reflects daytime activities, even though t…
Many psychologists believed that all motivation depended upon the pleasure experienced when basic needs are met. A person who is hungry, for instance, eats in order to reduce the tension that hunger produces. All human behavior could be attributed to the pleasure gained when these drive-induced tensions were reduced. Drive reduction theory lost favor over the years because it failed to explain hum…
Psychoactive drugs alter behavior, thought, or emotions by changing biochemical reactions in the nervous system. They can be addictive (habit-forming), and they can be legal or illegal. Drug abuse is the self-administration of drugs in ways that depart from medical or social norms, and it can lead to psychological or physical dependence. Physical dependence, or addiction, which can occur together …
Because research has shown that many psychiatric illnesses are biological in origin, drug therapy is often the prescribed treatment. Drug therapy is used to treat a variety of psychological disorders, including attention deficit/hyperactivity disorder (ADHD), major depression, schizophrenia, Tourette's syndrome, anxiety disorders, autism, panic attacks, and obsessive-compulsive disorder, am…
Although this term is used casually in popular culture, health care professionals define dysfunctional family as one where the relationships among family members are not conducive to emotional and physical health. Sexual or physical abuse, alcohol and drug addictions, delinquency and behavior problems, eating disorders, and extreme aggression are some conditions commonly associated with dysfunctio…
Dyslexia is a specific learning disability characterized by a significant disparity between an individual's general intelligence and his or her language skills, usually reflected in school performance. Estimates of people with dyslexia range from 2% to the National Institutes of Health figure of 15% of the U.S. population. It is a complicated disorder with no identifiable cause or cure, yet…
Eating disorders are rooted in complex emotional issues that center on self-esteem and pervasive societal messages that equate thinness with happiness. Eating disorders usually surface in adolescence, and more than 90% of sufferers are female, although the incidence among males appears to be growing. Because eating disorders are neither purely physical nor purely psychological, effective treatment…
Hermann Ebbinghaus (Corbis-Bettmann. Reproduced with permission.) Born in Germany, Hermann Ebbinghaus received his formal education at the universities of Halle, Berlin, and Bonn, where he earned degrees in philosophy and history. After obtaining his philosophy degree in 1873, Ebbinghaus served in the Franco-Prussian War. For the next seven years following the war, he tutored and studied in…
John Carew Eccles was a neurophysiologist whose research explained how nerve cells communicate with one another. He demonstrated that when a nerve cell is stimulated it releases a chemical that binds to the membrane of neighboring cells and activates them in turn. He further demonstrated that by the same mechanism a nerve cell can also inhibit the electrical activity of nearby nerve cells. For thi…
Using a mechanical, robot like speech pattern, an individual with certain mental disorders may repeat words or phrases spoken by others. Known as echolalia, this behavior is observed in children with autism, Tourette's syndrome, schizophrenia, and certain other brain disorders. …
Educational psychology departments in many universities provide training to educators, school psychologists, and other educational professionals. Applied research in this field focuses on how to improve teaching, solve learning problems, and measure learning ability and progress. Other concerns of educational psychology include cognitive development, the dynamics of pupil behavior, and the psychol…
An effector acts in special ways in response to a nerve impulse. In humans, effectors may either be muscles, which contract in response to neural stimuli, or glands, which produce secretions. The muscles are generally divided into two groupings: somatic effectors, which are the body's striated muscles (such as those found in the arm and back), and autonomic effectors, which are smooth muscl…
Sigmund Freud believed that human personality has three components: the id, the ego and the superego. In his scheme, the id urges immediate action on such basic needs as eating, drinking, and eliminating wastes without regard to consequences. The ego is that portion of the personality that imposes realistic limitations on such behavior. It decides whether id-motivated behavior is appropriate, give…
Electrical stimulation of the brain (ESB) is useful in a variety of situations, including neurosurgical operations and experimental research. In neurosurgery, this procedure may be used to assist physicians in determining which brain tissue should be removed. Because the patient must remain awake during the procedure, only a local anesthetic is administered. Focal epilepsy has been surgically trea…
Electroconvulsive therapy, also known as ECT and electroshock therapy, was developed in the 1930s when various observations led physicians to conclude that epileptic seizures might prevent or relieve the symptoms of schizophrenia. After experiments with insulin and other potentially seizure-inducing drugs, Italian physicians pioneered the use of an electric current to create seizures in schizophre…
Electroencephalography is used for a variety of research and diagnostic purposes. It is usually conducted using electrodes, metal discs attached to the scalp or to wires connected to the skull or even to the brain itself. The signals obtained through the electrodes must then be amplified in order to be interpreted. EEG patterns typically take the form of waves, which may be measured according to b…
Psychologist and educator David Elkind was born in Detroit, Michigan, to Peter and Bessie (maiden name Nelson) E. Elkind. He and his family moved to California when he was an adolescent. He received the Bachelor of Arts from the University of California at Los Angeles (UCLA) in 1952, and his Doctorate in Philosophy (Ph.D.) from UCLA in 1955. He also received an honorary Doctorate in Science from R…
Raised in the Bronx, New York, Albert Ellis was shy and physically frail when he was young. Although he had literary ambitions in his teens and twenties, he earned degrees in accounting and business. While in his twenties, he found that he had a gift for advising his friends on sexual matters and undertook an intensive independent study of human sexuality. Deciding to become a professional therapi…