Behavioral economics of drug self-administration. IV. The effects of response requirement on the consumption of and interaction between concurrently available coffee and cigarettes.

In behavioral economics, consumption of a reinforcer is determined by its price and by the price of other available reinforcers. This study examined the effects of price manipulations on the consumption of concurrently available coffee and cigarettes. During fifteen 4-h sessions, coffee and cigarettes were concurrently available according to fixed-ratio (FR) schedules of reinforcement. After consumption stabilized under a fixed ratio 100 for both reinforcers, the response requirement for each reinforcer was varied separately (i.e., FR 100, 1000 and 2500), while the response requirement for the other reinforcer was kept at 100. Increasing the FR value decreased coffee and cigarette consumption to a similar degree. Also, as the price for cigarettes increased (and consumption decreased), coffee consumption decreased; however, as the price of coffee increased, cigarette consumption did not change. These results indicate that for this setting the reinforcing effects of cigarettes and coffee were comparable but interacted asymmetrically. These findings when analyzed and quantified via economic concepts of own-price and cross-price elasticity illustrate the viability of using behavioral economics to examine drug self-administration in a choice paradigm.