Alcohol obviously impairs cognition, but here is a nuance you may not have heard before: the amount of alcohol in your blood has different effects depending on if it's rising or falling.
Think of your blood alcohol level as a ramp. It rises when you start drinking, then you get to the top of the ramp, stop drinking, and head down. On the way down, you'll hit all the same levels as you did on the way up, just coming the opposite direction. But like a ramp, elevation isn’t all that matters—the way up is more difficult than the way down.
One review found that, on many cognitive tasks, reaction time was impaired when blood alcohol was on the rise, but not when it was on the decline, even at the same level. Accuracy, however, was impaired regardless of when that level was reached.
In other words, accuracy stays bad when you're coming down from drunkenness, but reaction time may have recovered by that time.
Overall performance on most tasks will still be impaired regardless (so never drink and drive), but it shows how timing and context matter when it comes to a complex system like the brain.
See also:
- The Curious Case of the Memory-Boosting Alcohol
- Staying Up Late Makes You as Mentally Foggy as Being Drunk