People that participated in this study were divided into two groups and given alcoholic and non-alcoholic beverages. They were, of course, not aware if they took alcohol or not. They had ten minutes to finish with their drink and then they had to watch for a basketball match and count how many times the ball was passed between players.
Somewhere in the middle of the game, a gorilla walked into the screen, started thumping its chest and disappeared.

Those study participants who had an alcoholic beverage and tested mildly intoxicated were more likely not to spot the gorilla. Such findings suggest that even people who have been mildly intoxicated and had just the half of the legal intoxication limit have impaired judgment and cannot focus on all the things they should be focusing and may easily miss one of the things they should be watching for-like a pedestrian for example.