Concurrent schedules of cocaine injection in rhesus monkeys: dose variations under independent and non independent variable interval procedures

The purpose of this study was to rank the reinforcing efficacy of a range of cocaine doses by comparing them with a standard dose, and to compare concurrent schedule performances obtained by using intravenous cocaine as the reinforcer with concurrent schedule performances obtained by using other reinforcers. Under both concurrent scheduling procedures, even with very small dose differences monkeys reliably preferred the higher of two doses presented for comparison, suggesting that over the dose range examined, higher cocaine doses are more reinforcing than lower ones with which they are compared.