Wilhelm Wundt established the first psychological laboratory in 1879 in Germany. Two early schools were structuralism and functionalism.

Early researchers defined psychology as “the science of mental life.” In the 1920s, under the influence of John B. Watson and the behaviorists, the field’s focus changed to the “scientific study of observable behavior.” In the 1960s, the humanistic psychologists and the cognitive psychologists revived interest in the study of mental processes. Psychology is now defined as the science of behavior and mental processes.

Our growing understanding of biology and experience has fed psychology’s most enduring debate. The nature–nurture issue centers on the relative contributions of genes and experience, and their interaction in specific environments. Charles Darwin’s view that natural selection shapes behaviors as well as bodies led to evolutionary psychology’s study of our similarities because of our common biology and evolutionary history, and behavior genetics’ focus on the relative power and limits of genetic and environmental influences on behavior.
Cross-cultural and gender studies have diversified psychology’s assumptions while also reminding us of our similarities. Attitudes and behaviors may vary somewhat by gender or across cultures, but because of our shared human kinship, the underlying processes and principles are more similar than different.
Psychology’s traditional focus on understanding and treating troubles has expanded with positive psychology’s call for more research on human flourishing and its attempt to discover and promote traits that help people to thrive.

The biopsychosocial approach integrates information from three differing but complementary levels of analysis: the biological, psychological, and social-cultural. This approach offers a more complete understanding than could usually be reached by relying on only one of psychology’s current perspectives (neuroscience, evolutionary, behavior genetics, psychodynamic, behavioral, cognitive, and social-cultural).

Within the science of psychology, researchers may conduct basic research to increase the field’s knowledge base (often in biological, developmental, cognitive, personality, and social psychology) or applied research to solve practical problems (in industrial-organizational psychology and other areas).
Those who engage in psychology as a helping profession may assist people as counseling psychologists, helping people with problems in living or achieving greater well-being, or as clinical psychologists, studying and assessing people with psychological disorders and treating them with psychotherapy. (Psychiatrists also study, assess, and treat people with disorders, but as medical doctors, they may prescribe drugs in addition to psychotherapy.) Community psychologists work to create healthy social and physical environments (in schools, for example).

The testing effect shows that learning and memory are enhanced by actively retrieving, rather than simply rereading, previously studied material. The SQ3R study method—survey, question, read, retrieve, and review—applies principles derived from memory research. Four additional tips are (1) distribute your study time; (2) learn to think critically; (3) process class information actively; and (4) overlearn.