We know that good nutrition has a role in staving off mental decline. Now it seems there’s an even easier way to boost your short term memory: drink more water. Or at least make sure you’re drinking enough. This, according to a new study from Britain, which tested how volunteers reacted to 30 degree temparatures for four hours. Half were allowed to drink 300 millilitres of water and half were not.

Those who did not drink water found the tests more difficult to perform than those who hydrated during study, and their scores were lower. Previous work has also shown that being even just slightly dehydrated can impair attention and memory, and it is easy to get this minor degree of dehydration even in cool fall temparatures if you don’t drink water often enough. Dehydration can also reduce your mood, which in turn can affect memory.

The researchers say men need 12 to 13 cups of water and women need 9 cups. The good news is that all drinks except alcoholic one count towards that requirement. That includes beverages with caffeine. The work is published in the Journal of Clinical Nutrition.