Delay Discounting
Delay discounting is the fall in a reward's subjective value as the wait for it lengthens. Twenty pounds now and twenty pounds in a year are the same twenty pounds and they are not the same offer. Everybody discounts the future, and the variable that matters is how steeply, because a steep curve lets the immediate option beat an objectively larger delayed one. The behavioural finding that people with active addictions discount much more steeply is among the better-replicated results in the area. What is not settled is the direction of causation, and one widely repeated imaging claim built on this literature is a misreading that should not be passed on.
What it is
The idea does its main work in explaining why a person with an addiction is not making a stupid choice so much as making a choice on a differently shaped curve. The reward that is available now is not merely preferred. It is worth more, on the curve that person is actually using.
Popular accounts of this material tend to introduce the concept as though defining it fresh, and the formal study of discounting curves is usually absent from them. This publication records its own identification, and records it as unverified: hyperbolic discounting and the preference-reversal result are conventionally credited to George Ainslie, with the hyperbolic functional form usually given as Mazur's and the wider behavioural framework as Rachlin's. No year, journal or title for any of the three has been traced here, so none of those names should be printed in an article without going to the papers first.
Two behavioural findings carry the applied claim. In a lottery-ticket task reported by Bretteville-Jensen, people were offered less money now against more money later. About one in five active drug users took the smaller immediate sum, against roughly one in twenty-five former users and one in fifty matched controls. And in a study of temporal horizon by Petry, Bickel and Arnett, participants asked to imagine the future gave horizons averaging nine days when opioid-addicted, against nearly five years for controls. That second finding is the most quotable in the set and it is properly cited. Note the author order, because secondary coverage routinely gives the paper to Bickel and the first author is Petry.