Isolating behavioral mechanisms of intertemporal choice: nicotine effects on delay discounting and amount sensitivity.
Nicotine changes choice by making small rewards look bigger, not by making clients more impatient.
01Research in Context
What this study did
Matson et al. (2009) gave people choices between a small reward now or a bigger reward later. They repeated the test after giving nicotine gum or a placebo.
The team tracked two things: how long people were willing to wait (delay discounting) and how size changes shifted their pick (amount sensitivity).
What they found
Nicotine did not make people more impatient. Wait times stayed the same.
But nicotine did make the smaller-sooner reward more attractive. The drug tweaked amount sensitivity, not delay tolerance.
How this fits with other research
Collier et al. (1986) showed rats work harder when food pellets shrink. L et al. echo that idea: changing reward size, not timing, steers choice.
Bailey et al. (1990) also isolated amount in risky choice. Rats picked the safe pile more when pellet size grew. Both studies prove amount matters apart from delay or odds.
Hackenberg (2018) notes token economies follow the same rule: backup prize size controls exchange. The nicotine data extend that rule to pharmacology.
Why it matters
When you write a choice program, list both the delay and the amount columns. If a client suddenly prefers the tiny sticker now, ask: did medication, hunger, or token size change? Adjust the amount first; you may not need to shorten the wait.
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02At a glance
03Original abstract
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) on 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.
Journal of the experimental analysis of behavior, 2009 · doi:10.1901/jeab.2009.91-213