Preferring a smaller immediate payment over a larger delayed payment measures a particular kind of choice. It is not, by itself, proof of generalized impaired judgment. A 2008 methamphetamine study found group differences in such choices while also showing why task conditions and imaging contrasts matter.
The population and the comparison
Hoffman and colleagues recruited 20 treatment participants and 22 controls. Six had unusable imaging data, leaving 19 recently abstinent methamphetamine-dependent participants and 17 controls for analysis.
Treatment participants had been abstinent for approximately two to eight weeks under the recruitment criteria, and no participant tested positive on the evaluation drug screen. The study did not administer methamphetamine or measure an acute concentration–impairment relationship.
What was a delayed-reward choice?
Participants chose between $100 after a specified delay and a smaller immediate amount. A comparison task held either the amount or delay constant. The investigators distinguished difficult choices near each person’s indifference point from easier choices.
The methamphetamine group chose immediate rewards more often—approximately 65% versus 40% of choices—and showed steeper modeled discounting. These are proportions of repeated task choices, not percentages of participants proven incapable of making future-oriented decisions.
The groups did not significantly differ in reaction times on delay-discounting trials. More immediate choices should therefore not be described as evidence that participants universally responded faster or failed to consider the options.
The reference condition influenced the imaging contrast
Difficult choices activated several cognitive and affective regions across participants. Selected cortical contrasts were smaller in the treatment group. The paper notes that this partly reflected greater activation during easier and comparison trials, rather than simply absent activation during difficult choices.
An imaging contrast is a difference between conditions. Interpreting it as a direct amount of “brain function lost” ignores its reference condition.
The degree of discounting was associated with some regional responses across the combined sample. Some controls also discounted heavily. A group average therefore does not identify a behavior unique to methamphetamine dependence.
What remains uncertain?
The study was small, selected and observational. Smoking was more common in the methamphetamine group, and the task could not separate every stage of evaluation, comparison and response selection. Imaging limitations also affected sensitivity in some regions.
The findings do not establish that methamphetamine caused an individual’s choice preference, that a delayed-reward preference is permanent, or that it predicts conduct in every real-life setting. No clinical or forensic classification threshold was validated.
Appropriate interpretation
The study provides historical evidence of steeper discounting and particular imaging relationships in an abstinent treatment sample. It does not determine competence, intent, truthfulness, acute intoxication or safe driving. Applying its findings requires naming the measured choice process rather than replacing it with a broad label such as “bad judgment.”
Primary scientific source
Hoffman WF, Schwartz DL, Huckans MS, et al. Cortical activation during delay discounting in abstinent methamphetamine dependent individuals. Psychopharmacology. 2008;201(2):183–193. doi:10.1007/s00213-008-1261-1. Historical observational human imaging study.
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