Psychology is an applied and academic discipline that studies the human mind and behavior in order to understand and explain thoughts, emotions and actions. The word psychology comes from the Ancient Greek words psyche, which means spirit or soul, and logos, which means study.
Over the centuries psychology has been criticized for the lack of objective scientific methods, as it relied heavily on subjective perceptions, surveys and questionnaires. In response to these criticisms, today's psychology focuses more on objective scientific methods. It has given up its close relationship with philosophy and adopted more objective and trustworthy tools. Its research methods include qualitative and quantitative research, controlled experiments, surveys, longitudinal studies, observation in natural settings.
In ancient times psychology was a branch of both philosophy and biology. Discussions of psychological issues can be traced back to ancient civilizations in Egypt, Greece, China, India and Persia. De Anima, a treatise by Greek thinker Aristotle (384 to 322 BCE), is credited as the first major work about psychology in Western civilization.
Psychology became a separate science in the 19th century, when German physician Wilhelm Wundt (1832 to 1920) set up the first psychology laboratory in Leipzig, Germany. Wundt belonged to a school known as structuralism, whose aim was to describe the structures composing the mind. His research was based mostly on the analysis of sensations and feelings. This method, known as introspection, was criticized as being highly subjective.
Functionalism emerged as a reaction to structuralism and was strongly influenced by the evolutionary theory of Charles Darwin. In his landmark book Principles of Psychology (1890), American philosopher and psychologist William James (1842 to 1910) argued that the task of psychology is to focus on the purpose of consciousness and behavior. Functionalists tried to explain mental processes in a more systematic and accurate way compared to structuralists. This psychological school had a strong influence later on behaviorism and applied psychology. Its impact on the educational system is also recognized.
The 19th century development of psychology was also marked by the work done by Russian Nobel Prize winner Ivan Pavlov (1849 to 1936). While working in the field of physiology, his discovery of the so-called classical conditioning had a considerable impact on future psychologists. In particular, he was famous for the experiment with a dog, proving that the presentation of a stimulus necessarily evokes a reflexive response.
In the late 19th century and early 20th century, Austrian physician Sigmund Freud (1856 to 1939) developed psychoanalysis, which claimed that human behavior is determined by irrational, unconscious drives. He showed particular interest in the conflict between the conscious level and unconscious layers of the mind, finding out that this clash can result in mental disorders, including neurosis, neurotic traits, anxiety and depression.
The Freudian tenets had a strong impact on Swiss psychiatrist Carl Jung (1875 to 1961), the founder of analytical psychology. Jung elaborated on the role of archetypes in mental processes. The 1950s development of psychology in the United States was marked the emergence of behaviorism. Its eminent advocates include Edward Thomdike (1949-) and B.F. Skinner (1904-1990). The doctrine of behaviorism holds that behavior can be described and explained without any references to mental and psychological processes and therefore the sources of behavior are external, rather than internal. Humanistic psychology emerged in the 1950s in reaction to behaviorism. It adopted a holistic approach to the human. Its research covered meaning, values, freedom, human potential, spirituality and self-actualization.