Several of these procedures directly or indirectly measure the reinforcing effects of drug administration. Drug reinforcement refers to the ability of some drugs to motivate the individual to engage in behaviors leading to drug administration. This process is described technically as reinforcement and it is a fundamental principle in experimental psychology. Reinforcement theory has broad application in the study of both animal and human behavior. It has also been applied widely in the study of drug addiction.
Clinical methods use human subjects to study drug addiction in a laboratory setting.