One of the youngest sciences, psychology did not emerge as a formal discipline until the late 19th century. But its roots extend to the ancient past. For centuries, philosophers and religious scholars have wondered about the nature of the mind and the soul. Thus, the history of psychological thought begins in philosophy.


Philosophical Roots


The Greek physician Hippocrates was one of the first scholars to challenge the notion that disease was punishment sent from the gods. He believed that all illnesses, including mental illnesses, had natural origins.

From about 600 to 300 bc, Greek philosophers inquired about a wide range of psychological topics. They were especially interested in the nature of knowledge and how human beings come to know the world, a field of philosophy known as epistemology. The Greek philosopher Socrates and his followers, Plato and Aristotle, wrote about pleasure and pain, knowledge, beauty, desire, free will, motivation, common sense, rationality, memory, and the subjective nature of perception. They also theorized about whether human traits are innate or the product of experience. In the field of ethics, philosophers of the ancient world probed a variety of psychological questions: Are people inherently good? How can people attain happiness? What motives or drives do people have? Are human beings naturally social?

Early thinkers also considered the causes of mental illness. Many ancient societies thought that mental illness resulted from supernatural causes, such as the anger of gods or possession by evil spirits. Both Socrates and Plato focused on psychological forces as the cause of mental disturbance. For example, Plato thought madness results when a person’s irrational, animal-like psyche (mind or soul) overwhelms the intellectual, rational psyche. The Greek physician Hippocrates viewed mental disorders as stemming from natural causes, and he developed the first classification system for mental disorders. Galen, a Greek physician who lived in the 2nd century ad, echoed this belief in a physiological basis for mental disorders. He thought they resulted from an imbalance of the four bodily humors: black bile, yellow bile, blood, and phlegm. For example, Galen thought that melancholia (depression) resulted from a person having too much black bile.


Galen, a Greek physician who lived during the 2nd century ad, believed that mental disorders resulted from an imbalance of the four bodily humors: black bile, yellow bile, blood, and phlegm.

More recently, many other men and women contributed to the birth of modern psychology. In the 1600s French mathematician and philosopher René Descartes theorized that the body and mind are separate entities. He regarded the body as a physical entity and the mind as a spiritual entity, and believed the two interacted only through the pineal gland, a tiny structure at the base of the brain. This position became known as dualism. According to dualism, the behavior of the body is determined by mechanistic laws and can be measured in a scientific manner. But the mind, which transcends the material world, cannot be similarly studied.

René Descartes

In the 17th century, French philosopher Reneé Descartes proposed that only two substances ultimately exist: mind and body. He believed the two were entirely distinct, and interacted only through the pineal gland at the base of the brain.

English philosophers Thomas Hobbes and John Locke disagreed. They argued that all human experiences—including sensations, images, thoughts, and feelings—are physical processes occurring within the brain and nervous system. Therefore, these experiences are valid subjects of study. In this view, which later became known as monism, the mind and body are one and the same. Today, in light of years of research indicating that the physical and mental aspects of the human experience are intertwined, most psychologists reject a rigid dualist position. See Philosophy of Mind; Dualism; Monism.

Many philosophers of the past also debated the question of whether human knowledge is inborn or the product of experience. Nativists believed that certain elementary truths are innate to the human mind and need not be gained through experience. In contrast, empiricists believed that at birth, a person’s mind is like a tabula rasa, or blank slate, and that all human knowledge ultimately comes from sensory experience. Today, all psychologists agree that both types of factors are important in the acquisition of knowledge.


Physiological Roots

Hermann von Helmholtz

In the mid-19th century German scientist Hermann von Helmholtz conducted some of the first studies of color vision, hearing, and space perception.

Modern psychology can also be traced to the study of physiology (a branch of biology that studies living organisms and their parts) and medicine. In the 19th century, physiologists began studying the human brain and nervous system, paying particular attention to the topic of sensation. For example, in the 1850s and 1860s German scientist Hermann von Helmholtz studied sensory receptors in the eye and ear, investigating topics such as the speed of neural impulses, color vision, hearing, and space perception. Another important German scientist, Gustav Fechner, founded psychophysics, the study of the relationship between physical stimuli and our subjective sensations of those stimuli. Building on the work of his compatriot Ernst Weber, Fechner developed a technique for measuring people’s subjective sensations of various physical stimuli. He sought to determine the minimum intensity level of a stimulus that is needed to produce a sensation.

Charles Darwin

In 1859 English naturalist Charles Darwin published On the Origin of Species, in which he set forth his revolutionary theory of evolution. Darwin’s theory led to comparisons between humans and other animals and was influential in the development of psychology.

English naturalist Charles Darwin was particularly influential in the development of psychology. In 1859 Darwin published On the Origin of Species, in which he proposed that all living forms were a product of the evolutionary process of natural selection. Darwin had based his theory on plants and nonhuman animals, but he later asserted that people had evolved through similar processes, and that human anatomy and behavior could be analyzed in the same way. Darwin’s theory of evolution invited comparisons between humans and other animals, and scientists soon began using animals in psychological research.

Jean Martin Charcot

French neurologist Jean Martin Charcot shows colleagues a female patient with hysteria at La Salpêtrière, a Paris hospital. Charcot gained renown throughout Europe for his method of treating hysteria and other “nervous disorders” through hypnosis. Charcot’s belief that hysteria had psychological rather than physical origins influenced Austrian neurologist Sigmund Freud, who studied under Charcot.

In medicine, physicians were discovering new links between the brain and language. For example, French surgeon Paul Broca discovered that people who suffer damage to a specific part of the brain’s left hemisphere lose the ability to produce fluent speech. This area of the brain became known as Broca’s area. A German neurologist, Carl Wernicke, reported in 1874 that people with damage to a different area of the left hemisphere lose their ability to comprehend speech. This region became known as Wernicke’s area.

Other physicians focused on the study of mental disorders. In the late 19th century, French neurologist Jean Charcot discovered that some of the patients he was treating for so-called nervous disorders could be cured through hypnosis, a psychological—not medical—form of intervention. Charcot’s work had a profound impact on Sigmund Freud, an Austrian neurologist whose theories would later revolutionize psychology.


Pseudoscientific Schools of Thought

Phrenological Chart

Phrenologists believed it was possible to link psychological traits to specific areas of the brain by measuring the bumps and indentations on a person’s skull. Phrenology enjoyed popularity among the lay public during the late 18th and early 19th centuries, but it was eventually discredited as unscientific. Scientists later proved the more general idea that certain mental activities are linked to specific areas of the brain.

Psychology was predated and somewhat influenced by various pseudoscientific schools of thought—that is, theories that had no scientific foundation. In the late 18th and early 19th centuries, Viennese physician Franz Joseph Gall developed phrenology, the theory that psychological traits and abilities reside in certain parts of the brain and can be measured by the bumps and indentations in the skull. Although phrenology found popular acceptance among the lay public in western Europe and the United States, most scientists ridiculed Gall’s ideas. However, research later confirmed the more general point that certain mental activities can be traced to specific parts of the brain.

Early “Treatments” for Mental Illness

Physicians in the 18th and 19th centuries used crude devices to treat mental illness, none of which offered any real relief. The circulating swing, top left, was used to spin depressed patients at high speed. American physician Benjamin Rush devised the tranquilizing chair, top right, to calm people with mania. The crib, bottom, was widely used to restrain violent patients.

Another Viennese physician of the 18th century, Franz Anton Mesmer, believed that illness was caused by an imbalance of magnetic fluids in the body. He believed he could restore the balance by passing his hands across the patient’s body and waving a magnetic wand over the infected area. Mesmer claimed that his patients would fall into a trance and awaken from it feeling better. The medical community, however, soundly rejected the claim. Today, Mesmer’s technique, known as mesmerism, is regarded as an early forerunner of modern hypnosis.


The Birth of Psychology as a Science

Wilhelm Wundt

German physiologist Wilhelm Wundt is generally considered the founder of psychology as a scientific discipline. He established the first laboratory for experimental psychology in 1879 at the University of Leipzig in Leipzig, Germany.

Modern psychology is deeply rooted in the older disciplines of philosophy and physiology. But the official birth of psychology is often traced to 1879, at the University of Leipzig, in Leipzig, Germany. There, physiologist Wilhelm Wundt established the first laboratory dedicated to the scientific study of the mind. Wundt’s laboratory soon attracted leading scientists and students from Europe and the United States. Among these were James McKeen Cattell, one of the first psychologists to study individual differences through the administration of “mental tests”; Emil Kraepelin, a German psychiatrist who postulated a physical cause for mental illnesses and in 1883 published the first classification system for mental disorders; and Hugo Münsterberg, the first to apply psychology to industry and the law. Wundt was extraordinarily productive over the course of his career. He supervised a total of 186 doctoral dissertations, taught thousands of students, founded the first scholarly psychological journal, and published innumerable scientific studies. His goal, which he stated in the preface of a book he wrote, was “to mark out a new domain of science.”

Compared to the philosophers who preceded him, Wundt’s approach to the study of mind was based on systematic and rigorous observation. His primary method of research was introspection. This technique involved training people to concentrate and report on their conscious experiences as they reacted to visual displays and other stimuli. In his laboratory, Wundt systematically studied topics such as attention span, reaction time, vision, emotion, and time perception. By recruiting people to serve as subjects, varying the conditions of their experience, and then rigorously repeating all observations, Wundt laid the foundation for the modern psychology experiment.

William James

Harvard University professor William James laid the foundations of American psychology with his book Principles of Psychology (1890), in which he wrote about consciousness, emotions, the self, and many other psychological topics. James’s ideas influenced generations of psychologists.

In the United States, Harvard University professor William James observed the emergence of psychology with great interest. Although trained in physiology and medicine, James was fascinated by psychology and philosophy. In 1875 he offered his first course in psychology. In 1890 James published a two-volume book entitled Principles of Psychology. It immediately became the leading psychology text in the United States, and it brought James a worldwide reputation as a man of great ideas and inspiration. In 28 chapters, James wrote about the stream of consciousness, the formation of habits, individuality, the link between mind and body, emotions, the self, and other topics that inspired generations of psychologists. Today, historians consider James the founder of American psychology.

James’s students also made lasting contributions to the field. In 1883 G. Stanley Hall (who also studied with Wundt) established the first true American psychology laboratory in the United States at Johns Hopkins University, and in 1892 he founded and became the first president of the American Psychological Association. Mary Whiton Calkins created an important technique for studying memory and conducted one of the first studies of dreams. In 1905 she was elected the first female president of the American Psychological Association. Edward Lee Thorndike conducted some of the first experiments on animal learning and wrote a pioneering textbook on educational psychology.

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