EVIDENCE LIBRARY
Can Alcohol Increase Attention Errors Without Clear Reaction-Time Slowing?
A 24-person crossover experiment found increased attentional errors with relatively little effect on measured response times. Reaction speed alone did not capture the performance change.
Yes. In a 24-person experiment, alcohol increased attention errors while measured reaction times were relatively unchanged. The result shows why an assessment based only on how quickly someone responds can miss a different dimension of performance. It does not mean reaction time is never affected by alcohol.
What the experiment compared
Benson and colleagues studied twelve women and twelve men aged 18–40. Each completed four randomized, counterbalanced sessions: alcohol, energy drink, both, and matched placebos.
Alcohol was administered at 0.6 grams per kilogram of body weight. The energy drink was a 250-milliliter serving containing eighty milligrams of caffeine. Participants completed tablet-based tests at baseline and forty-five, ninety and 180 minutes after treatment.
Exposure was checked with a breath analyzer, rather than direct blood sampling. Alcohol-only and combined-drink readings did not differ significantly at the two reported post-drink checks. The study therefore did not establish that an energy drink removed alcohol.
Attention accuracy was consistently sensitive to alcohol
The attention tests required choosing among four response locations, comparing digits within a number string and finding a target letter among distractors. Alcohol significantly increased errors on all three measures and on their combined attention-error score.
The attention composite’s alcohol effect had p = .002. The authors reported that the principal alcohol effects on attention accuracy would remain after adjustment for multiple comparisons, although the original analyses were uncorrected.
There was no significant effect on the composite attention reaction-time measure, and visual-search response time did not show significant treatment effects. The number-pairs response-time analysis showed a more complicated interaction involving drink and time.
Four-choice reaction-time data were lost because of software failure. Its error data were available, but the experiment cannot support a claim about preserved response speed on that particular task.
A speed–accuracy trade-off describes outcomes, not a proven mechanism
The authors described a shift toward more mistakes without compensatory slowing. That is different from uniformly slow and inaccurate performance.
They suggested that alcohol might impair calibration of one’s own errors. This study did not directly establish that explanation. The observed accuracy pattern can be reported without assuming that every participant was overconfident or unaware of mistakes.
Working-memory findings were less uniform. Alcohol increased errors on a serial-subtraction task, but the combined working-memory error score did not show a significant effect. The attention result should not be generalized to every cognitive domain.
Energy-drink comparisons did not produce a uniform correction
The combined drink produced more visual-search errors than alcohol alone at forty-five minutes, while selected memory or symbol-matching comparisons favored the combination at other times. There was no consistent benefit across tasks and time points.
These mixed secondary results are not the same as the main attention-error finding. Numerous comparisons were made, and not all findings would survive multiplicity adjustment.
Limits for a DUI assessment
The selected sample was small and included habitual caffeine consumers who abstained before testing. Caffeine-withdrawal reversal, test timing and possible awareness of beverage contents limit interpretation. The energy-drink manufacturer supplied beverages, and author relationships with industry were disclosed; the paper reported no company role in study design or interpretation.
No driving task or person-specific impairment cutoff was validated. The defensible inference is that prompt responding does not, by itself, exclude an accuracy deficit. The site’s word-decision study found a different pattern, with clearer slowing than accuracy loss. The endpoint and task therefore matter.
Primary source
Benson S, Tiplady B, Scholey A. Attentional and working memory performance following alcohol and energy drink: A randomised, double-blind, placebo-controlled, factorial design laboratory study. PLOS ONE. 2019;14:e0209239. https://doi.org/10.1371/journal.pone.0209239.