The objective of this study was to examine the effects of alcohol on cognitive performance with increasing blood alcohol concentration (BAC), as measured by the King-Devick (KD) test and Mobile Universal Lexicon Evaluation System (MULES).


Cognitive impairments from alcohol consumption may manifest on tests that assess cognitive function, such as the KD test and MULES. Studies suggest that the threshold for detecting impairment from concussion is 3-seconds on KD testing and 4-seconds on MULES; however, a similar threshold has not been identified for detecting alcohol intoxication.


Eleven subjects (7 females, 4 males; ages 21-39) participated in four, 20-minute blocks of alcohol consumption, 10 minutes of rest with BAC measurement, and KD and MULES testing. The KD and MULES testing focused on performance time, while KD also evaluated the number of saccades/blinks. Women received alcohol (vodka in orange juice) doses of 0.75+/-0.1 g/kg body mass and men received 1.0 +/- 0.1 g/kg body mass.


On average, each 20-minute period of consuming alcohol raised BAC by 0.02. There was a statistically significant effect of BAC on both the KD (p<0.001) and MULES (p<0.001) performance times. Specifically, KD times demonstrated a ≥3 sec increase at a BAC of 0.08, while the ≥4 sec threshold was reached at a BAC of 0.06 for the MULES testing. No statistical differences were noted between BAC and saccades or numbers of blinks during the KD test (p>0.05).


At a BAC of 0.08, KD test time exceeded 3 seconds, consistent with thresholds used to diagnose concussion. However, the ≥4 seconds threshold was achieved with a BAC of 0.06 for the MULES test. Thus, the MULES test may be a more sensitive measure of alcohol intoxication. Further studies with larger sample sizes are warranted to further characterize changes in testing times resulting from increasing BAC.

Summary Points:

  • K-D Test scores were significantly slower as blood alcohol concentration increased.
  • A blood alcohol concentration of 0.08 resulted in a 3-second increase in K-D Test scores, which is similar to changes observed following a concussion.
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