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The early 20th century refers to the time period from approximately 1900 to 1940 when significant advancements were made in various fields, including psychology and neuroscience.
Behaviorism is a school of thought in psychology that focuses on observable behavior rather than internal mental processes.
Neurotransmitters are chemical messengers that transmit signals between neurons in the brain and nervous system.
Psychopharmacology is the study of how drugs affect behavior and mental processes.