Measuring the Reinforcing Strength of Abused Drugs

Bimodality of function in self-administration studies. In this graph, the dose per injection is shown along the abscissa. The number of injections that are self-administered (reinforcers) is shown along the ordinate. Note that low and high unit doses of cocaine and heroin result in few reinforcer deliveries, whereas intermediate doses of either drug result in the greatest self-administration. As discussed in text, this type of dose-response relationship is not easily interpreted in terms of reinforcing strength.