Summary of “Mental Performance Can Be Hurt By Even Mild Dehydration”

Now there’s evidence that too little water can hurt cognitive performance, too, making complex thinking tasks harder.
A growing body of evidence finds that being just a little dehydrated is tied to a range of subtle effects – from mood changes to muddled thinking.
How long does it take to become mildly dehydrated in the summer heat? Not long at all, studies show, especially when you exercise outdoors.
For an average-size person, 2 percent dehydration equates to sweating out about a liter of water.
“Most people can’t perceive that they’re 1.5 percent dehydrated,” Casa says.
Already there are subtle – maybe even imperceptible – effects on our bodies and our mental performance.
“We did manage to dehydrate them by [about] 1 percent just by telling them not to drink for the day,” says Nina Stachenfeld, of the Yale School of Medicine and the John B. Pierce Laboratory, who led the research.
Dehydration didn’t hamper performance on all the tests; the women’s reaction time, for example, was not impeded.

The orginal article.