The United States is experiencing a major heat wave right now, and hopefully you’re doing your best to stay hydrated – not just for your body, but for your brain as well, according to a new study conducted at the University of East London School of Psychology.

Subjects in the study, which was admittedly small, consumed about 24 ounces of water and performed better on several mental tests than subjects who didn’t drink any water immediately before the test. Test scores were even worse for individuals who went into the test feeling thirsty, leading researchers to conclude that mental response time may be slowed by the distraction of thirst. The study results might not be too surprising, however, as water consumption is well-known to have many benefits including calorie control, body fluid maintenance, improved kidney function, and healthy skin.

Drinking Water Improves Reaction Time

The study involved 34 healthy adults who stopped all eating and drinking (including water, of course) beginning at 9:00 in the evening. The very next day, they underwent a series of mental tests in a laboratory environment. This happened twice, with subjects being given a cereal bar and 24 ounces of water one morning and just a cereal bar without water the next morning.

One particular test that showed a marked difference between those who did and didn’t drink water beforehand was a reaction test. Those who drank water scored about 14% better on average than those who didn’t drink water. There didn’t seem to be much of a difference in test scores between those who drank water and those who didn’t on a word memory test. However, a previous study on children found that getting proper hydration resulted in improved memory test scores, and a previous study on adults found that dehydration resulted in weakened mental performance. Of course, getting proper hydration throughout the day is different from drinking water immediately before a test, so the comparison is less than fair.

But it Doesn’t Always Hold True

Unfortunately, a separate study found the opposite: that drinking water prior to a test actually reduces cognitive functioning, although this particular test was focused on learning rules.

Caroline Edmonds, one of the lead researchers behind the study, said that whether or not drinking water improves a person’s ability to perform a task may depend on the specific task in question. Edmonds theorizes that this could have something to do with vasopressin, the hormone responsible for making you feel thirsty when you’re lacking hydration. Some studies have found that vasopressin can influence arousal, awareness and attention.

Regardless of any study data, common sense and established medical reasoning dictate that you should drink plenty of water, especially in the summer, in order to support all types of bodily functioning.

The Bottom Line

A new study from England suggests that drinking water may improve your reaction time, though the same improvements were not observed in memory tests. The full text of the study can be found online in the medical journal Frontiers in Human Neuroscience.