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Log response- and time-allocation ratios plotted as a function of log injection ratios with concurrent 0.1 µg/kg/inj remifentanil and 56 µg/kg/inj cocaine. Squares represent log ratios of behavior with 0.1 µg/kg/inj remifentanil on the left lever and 56 µg/kg/inj cocaine on the right and circles represent the lever reversal. Other details are as in Figure 3.
