[MUSIC PLAYING] - Psychology began to emerge as a field distinct from philosophy in the 19th Century. Prior to this, philosophers such as Plato, Aristotle, and Descartes explored the causes of behavior and the nature of the mind, but in 1879, German physician Wilhelm Wundt established the first laboratory within the philosophy department at the University of Leipzig with the goal of applying the experimental methods of natural science to philosophical problems. 

Specifically, Wundt believed that he could understand the structure of the mind through introspection, close examination of one's own conscious experience. This school of thought became known as structuralism, as wundt believed that introspection would eventually reveal the hidden structures of the mind. Even though it has been replaced with more objective measures, this work represents the beginning of psychology as a science because it showed that mental processes could be quantified. 

Another important early psychologist was American William James. He built upon Charles Darwin's ideas about natural selection. Specifically, he proposed that, much like our physical characteristics, humans psychological characteristics evolved because they were functional. They provided some kind of evolutionary advantage. 

This school of thought became known as functionalism, and it was focused on understanding how specific mental processes helped people survive and adapt to their environment. These days, this work has evolved into a branch of study called evolutionary psychology, which attempts to explain psychological processes such as perception, language, and memory as being the product of evolutionary adaptation. 

Sigmund Freud is considered the father of psychoanalysis, or Freudian psychology, which focuses on the role of the unconscious in shaping behavior. Freud believed that behavior was driven by forgotten childhood experiences and unconscious desires. He developed psychoanalytic treatment approaches intended to treat psychological symptoms by bringing unconscious material into conscious awareness through the analysis of dreams and talk therapy. 

Freud's work also inspired other psychologists, such as Carl Jung, Eric Erikson, Alfred Adler, and Karen Horney. Each of these theorists shared Freud's beliefs about the importance of early childhood experiences, but they felt that Freud overemphasized certain factors like sexual desires, and that he had an overly negative view of human nature. They began to explore other motivators, such as the drive to achieve or to build close connections. 

Many of Freud's ideas were not falsifiable, and therefore, not scientific. For example, it's not possible to test whether a person's behavior is influenced by an undetectable unconscious desire. As psychology developed, it became more scientific, and later schools of thought shifted away from psychoanalytic perspectives to focus on testable hypotheses about the causes of thoughts, feelings, and behaviors.