SPECIAL FIELDS OF PSYCHOLOGY

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.

3.Psychoanalysis

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.