What Memory, Attention and Alertness Tests Measure in Brain Supplement Trials

Memory, attention and alertness in plain words

• Memory. MedlinePlus describes short-term memory as storing information for a few seconds or minutes, and long-term memory as storing it for longer. [1] Trials often test recall straight after learning and again after a delay. [2]
• Attention. Attention covers staying focused over time and shifting focus. The next section shows how tasks separate these.
• Alertness. This usually means how fast and how steadily someone responds, which sleep loss affects. [3]

For how these abilities work in everyday life, see how attention and memory work.

Common tests and what the sources say they measure

The screening tests belong to clinical care, not to trials of focus supplements. Doctors may repeat them over time to see how a person's thinking changes. [7] A review of the MoCA for detecting MCI found the included studies at high or unclear risk of bias in every area except the reference standard, which limits confidence in the cut-off scores. [8]

Why one number can mislead

Simple tasks and complex tasks are not the same. A meta-analysis found complex task performance may not be hurt by sleep disruption as severely as simple task performance. [11]

Practice raises scores. In healthy young adults who repeated the same tasks, practice effects appeared for all tasks and were reduced but not fully removed at later visits. [2] A trial without a placebo group cannot separate practice from a supplement.

Composite scores hide detail. COSMOS-Mind used a global composite built from standardized scores of several tests. [5] A small change in a composite is a statistical result. It does not tell you how a person's day went.

Lab tasks are not everyday performance. In the PVT study, three of four aviation-related tasks showed strong correlation with the 3-minute PVT, while a transportation task showed lower correlations. [3] Some links exist, but they are task-specific and were tested in sleep and alcohol conditions, not supplements.

What to ask of any study or claim

1. Which test was used, and does it match the claim (memory, attention or speed)?
2. Was there a placebo group, to account for practice?
3. Who was studied? See why results do not transfer between groups.
4. Was the outcome a test score, or a diagnosis or daily function?

A ranking of which cognitive test best captures a true supplement effect: Proper evidence not found. We searched PubMed for reviews of cognitive outcome measures in nutrition trials and found individual studies, such as the practice-effects study, but no source we could read that ranks tests. For how trials are built, see how brain supplement trials are designed, and for outcome-by-outcome results see nootropic evidence by outcome.