The withdrawal symptoms that occur in heroin addicts are less dangerous than those that occur in alcoholics. Withdrawal symptoms are primarily the opposite of the effects of the drug itself. The most appropriate definition of drug addiction would emphasize negative personal, legal, and social effects of drug taking. Drugs that do not produce physical dependence can still be addictive. A reinforcing stimulus is most effective if it occurs immediately after the behavior.
Positive reinforcement works better in humans than in laboratory animals.
Immediacy of reinforcement takes precedence over quantity. Addictive drugs can trigger the release of dopamine in the nucleus accumbens by stimulating the reuptake of dopamine by terminal buttons. Lamb et al. Negative reinforcement does not refer to a behavior that reduces an aversive stimulus. All of the following are compensatory mechanisms that have been proposed to explain the phenomena of tolerance to and withdrawal from drugs except down regulation of opiate receptors.