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SPECIAL FIELDS OF PSYCHOLOGY
2. Physiological psychology
5. Gestalt psychology
7. Tests and Measurements
8. Development psychology
9. Social psychology
10. Psychiatry and mental health
11. Forensic psychology and criminology
12. Psychology, religion and phenomenology
14. Industrial Psychology
Psychology, scientific study of behavior and experience—that is, the study of how human beings and animals sense, think, learn, and know. Modern psychology is devoted to collecting facts about behavior and experience and systematically organizing such facts into psychological theories. These theories aid in understanding and explaining people’s behavior and sometimes in predicting and influencing their future behavior.
Psychology, historically, has been divided into many subfields of study; these fields, however, are interrelated and frequently overlap. Physiological psychologists, for instance, study the functioning of the brain and the nervous system, and experimental psychologists devise tests and conduct research to discover how people learn and remember. Subfields of psychology may also be described in terms of areas of application. Social psychologists, for example, are interested in the ways in which people influence one another and the way they act in groups. Industrial psychologists study the behavior of people at work and the effects of the work environment. School psychologists help students make educational and career decisions. Clinical psychologists assist those who have problems in daily life or who are mentally ill.
History. The science of psychology developed from many diverse sources, but its origins as a science may be traced to ancient Greece.
Philosophical Beginnings. Plato and Aristotle, as well as other Greek philosophers, took up some of the basic questions of psychology that are still under study: Are people born with certain skills, abilities, and personality, or do all these develop as a result of experience? How do people come to know the world? Are certain ideas and feelings innate, or are they all learned?
Such questions were debated for many centuries, but the roots of modern psychological theory are found in the 17th century in the works of the French philosopher Ren Descartes and the British philosophers Thomas Hobbes and John Locke. Descartes argued that the bodies of people are like clockwork machines, but that their minds (or souls) are separate and unique. He maintained that minds have certain inborn, or innate, ideas and that these ideas are crucial in organizing people’s experiencing of the world. Hobbes and Locke, on the other hand, stressed the role of experience as the source of human knowledge. Locke believed that all information about the physical world comes through the senses and that all correct ideas can be traced to the sensory information on which they are based.
Most modern psychology developed along the lines of Locke’s view. Some European psychologists who studied perception, however, held onto Descartes’s idea that some mental organization is innate, and the concept still plays a role in theories of perception and cognition.
Against this philosophical background, the field that contributed most to the development of scientific psychology was physiology—the study of the functions of the various organ systems of the body. The German physiologist Johannes Miller tried to relate sensory experience both to events in the nervous system and to events in the organism’s physical environment. The first true experimental psychologists were the German physicist Gustav Theodor Fechner and the German physiologist Wilhelm Wundt. Fechner developed experimental methods for measuring sensations in terms of the physical magnitude of the stimuli producing them. Wundt, who in 1879 founded the first laboratory of experimental psychology in Leipzig, Germany, trained students from around the world in this new science.
Physicians who became concerned with mental illness also contributed to the development of modern psychological theories. Thus, the systematic classification of mental disorders developed by the German psychiatric pioneer Emil Kraepelin remains the basis for methods of classification that are now in use. Far better known, however, is the work of Sigmund Freud, who devised the system of investigation and treatment known as psychoanalysis. In his work, Freud called attention to instinctual drives and unconscious motivational processes that determine people’s behavior. This stress on the contents of thought, on the dynamics of motivation rather than the nature of cognition in itself, exerted a strong influence on the course of modern psychology.
Modern psychology still retains many aspects of the fields and kinds of speculation from which it grew. Some psychologists, for example, are primarily interested in physiological research, others are medically oriented, and a few try to develop a more encompassing, philosophical understanding of psychology as a whole. Although some practitioners still insist that psychology should be concerned only with behavior—and may even deny the meaningfulness of an inner, mental life—more and more psychologists would now agree that mental life or experience is a valid psychological concern.
The areas of modern psychology range from the biological sciences to the social sciences.
2. Physiological psychology
The study of underlying physiological bases of psychological functions is known as physiological psychology. The two major communication systems of the body—the nervous system and the circulatory system—are the focus of most research in this area.
The nervous system consists of the central nervous system (the brain and the spinal cord) and its outlying neural network, the peripheral nervous system; the latter communicates with the glands and muscles and includes the sensory receptors for seeing, hearing, smelling, tasting, touching, feeling pain, and sensing stimuli within the body. The circulatory system circulates the blood and also carries the important chemical agents known as hormones from the glands to all parts of the body. Both these communication systems are very important in overall human behavior.
The smallest unit of the nervous system is the single nerve cell, or neuron. When a neuron is properly stimulated, it transmits electrochemical signals from one place in the system to another. The nervous system has 12.5 billion neurons, of which about 10 billion are in the brain itself.
One part of the peripheral nervous system, the somatic system, transmits sensations into the central nervous system and carries commands from the central system to the muscles involved in movement. Another part of the peripheral nervous system, the autonomic system, consists of two divisions that have opposing functions. The sympathetic division arouses the body by speeding the heartbeat, dilating the pupils of the eye, and releasing adrenaline into the blood. The parasympathetic division operates to calm the body by reversing these processes.
A simple example of communication within the nervous system is the spinal arc, which is seen in the knee-jerk reflex. A tap on the patellar tendon, just below the kneecap, sends a signal to the spinal cord via sensory neurons. This signal activates motor neurons that trigger a contraction of the muscle attached to the tendon; the contraction, in turn, causes the leg to jerk. Thus, a stimulus can lead to a response without involving the brain, via a connection through the spinal cord.
Circulatory communication is ordinarily slower than nervous-system communication. The hormones secreted by the body’s endocrine glands circulate through the body, influencing both structural and behavioral changes . The sex hormones, for example, that are released during adolescence effect many changes in body growth and development as well as changes in behavior, such as the emergence of specific sexual activity and the increase of interest in the opposite sex. Other hormones may have more direct, short-term effects; for instance, adrenaline, which is secreted when a person faces an emergency, prepares the body for a quick response—whether fighting or flight.
Psychoanalysis, name applied to a specific method of investigating unconscious mental processes and to a form of psychotherapy. The term refers, as well, to the systematic structure of psychoanalytic theory, which is based on the relation of conscious and unconscious psychological processes.
Theory of Psychoanalysis
The technique of psychoanalysis and much of the psychoanalytic theory based on its application were developed by Sigmund Freud. His work concerning the structure and the functioning of the human mind had far-reaching significance, both practically and scientifically, and it continues to influence contemporary thought.
The first of Freud’s innovations was his recognition of unconscious psychiatric processes that follow laws different from those that govern conscious experience. Under the influence
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