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Research Summary

Moderate Drinking Impairs the Ability to See

Drinking alcohol clearly impairs the ability to drive. To determine whether this impairment is partly due to inattentional blindness—the inability to detect unexpected but visually-salient objects—researchers conducted a randomized study of 46 adults, aged 21–35 years, who were not heavy drinkers.

Subjects received either alcohol or tonic (placebo). Some were accurately told which beverage they received, while others were misinformed. The amounts of alcohol administered were enough to achieve a blood alcohol level of 0.04.

After consuming the beverage, each subject watched a video of teams passing a basketball back and forth. Subjects were asked how many times a particular team passed the ball and whether they noticed the person in a gorilla costume who briefly appeared in the video.

  • Only 33% of subjects noticed the “gorilla.”
  • Subjects who received alcohol were less likely than those who received placebo to notice the gorilla (18% vs. 46%, respectively).
  • Telling subjects the content of their beverages did not affect results (30% who were told they received alcohol and 33% who were told they received placebo noticed the gorilla).


This study suggests that inattentional blindness is more common when people drink than when they abstain. This is particularly concerning given that subjects who received alcohol in this study had a blood alcohol level that was half the legal driving limit in most states. The public should be informed that even low-level drinking before driving is risky.

Rosanne T. Guerriero, MPH
Richard Saitz, MD, MPH


Clifasefi SL, Takarangi MKT, Bergman JS. Blind drunk: the effects of alcohol on inattentional blindness. Appl Cognit Psychol. 2006;20(5):697–704.