This timeline document outlines the development of abnormal psychology from ancient times to the present day. It includes important individuals such as Hippocrates, Plato, Aristotle, and Galen in ancient times. In the Middle Ages, figures like Avicenna and Hildegard are noted. The 16th through 18th centuries section highlights individuals including Paracelsus, Weyer, Pinel, and Rush who contributed to understanding abnormal psychology. The 19th through early 20th centuries section lists psychologists such as Mesmer, Dix, Kraepelin, Wundt, Skinner, Pavlov, Watson, and Freud.