When an expert claims that methamphetamine necessarily worsens performance, the first scientific question is what “performance” means. A claim about every cognitive or psychomotor function is broader than a claim about a particular task.
Two affirmative findings worth examining
Hart and colleagues’ 2008 experiment found improved divided-attention tracking and response latency in experienced methamphetamine users; intermediate doses also improved digit-symbol substitution measures. Kirkpatrick and colleagues’ 2012 comparison found improved divided-attention performance after methamphetamine administration. Neither experiment demonstrated improvement on every tested function. [1,2]
These studies provide a concrete basis for asking an expert to define and support the scope of a claim. The useful question is whether the claimed impairment concerns a function actually measured by the cited research.
Questions that test the scientific reasoning
- Are you claiming impairment of a specific function, or deterioration in every cognitive and psychomotor function?
- Have you considered controlled studies that reported improved tracking speed or response latency after methamphetamine administration?
- Which measured outcome supports your conclusion about this person?
- How do the study participants, administration route, and assessment timing compare with the facts under review?
- Does the research establish the particular real-world activity you are discussing, or only performance on a laboratory task?
Avoid the reverse overstatement
A performance-enhancement finding does not itself prove that an individual was unimpaired. It establishes what happened under the experiment’s conditions. An expert who relies on that result still needs to explain its relevance to the person, activity, and time at issue.
The same discipline applies to both sides of a scientific dispute. An impairment claim should not erase documented improvements; an improvement claim should not erase the boundaries of the experiment. The strongest use of these studies is a precise challenge to an overbroad proposition, followed by an analysis of the actual evidence.
References
- Hart CL, et al. (2008). Acute Physiological and Behavioral Effects of Intranasal Methamphetamine in Humans. DOI: 10.1038/sj.npp.1301578.
- Kirkpatrick MG, et al. (2012). Comparison of intranasal methamphetamine and d-amphetamine self-administration by humans. DOI: 10.1111/j.1360-0443.2011.03706.x.