Journal
JOURNAL OF THE EXPERIMENTAL ANALYSIS OF BEHAVIOR
Volume 91, Issue 2, Pages 213-223Publisher
SOC EXP ANALYSIS BEHAVIOR INC
DOI: 10.1901/jeab.2009.91-213
Keywords
risk; impulsive choice; reinforer delay; reinforcer amount; nicotine; lever press; rats
Funding
- NIDA NIH HHS [F31 DA021442] Funding Source: Medline
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Many drugs of abuse produce changes in impulsive choice, that is, choice for a smaller-sooner reinforcer over a larger-later reinforcer. Because the alternatives differ in both delay and amount, it is not clear whether these drug effects are due to the differences in reinforcer delay or amount.. To isolate the effects of delay, we used a titrating delay procedure. In phase 1, 9 rats made discrete choices between variable delays (1 or 19 s, equal probability of each) and a delay to a single food pellet. The computer titrated the delay to a single food pellet until the rats were indifferent between the two options. This indifference delay was used as the starting value for the titrating delay for all future sessions. We next evaluated the acute effects, of nicotine (subcutaneous 1.0, 0.3, 0.1, and 0.03 mg/kg) oil choice. If nicotine increases delay discounting, it should have increased preference for the variable delay. Instead, nicotine had very little effect on choice. In a second phase, the titrated delay alternative produced three food pellets instead of one, which was again produced by the variable delay (1 s or 19 s) alternative. Under this procedure, nicotine increased preference for the one pellet alternative. Nicotine-induced changes in impulsive choice are therefore likely due to differences in reinforcer amount rather than differences in reinforcer delay. In addition, it may be necessary to include an amount sensitivity parameter in any mathematical model of choice when the alternatives differ in reinforcer amount.
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