If making the simplest of decisions seems difficult in this high twenties (or, yikes, thirties) heat, you are not alone.

Simply put, the warmer it gets, the harder it is to think. And the less we even want to think.

It has long been known the brain suffers as the body dehydrates. Recent studies have also found it only takes a little dehydration to make a huge difference to our power to think.

"Being dehydrated by just 2 per cent impairs performance in tasks that require attention, psychomotor, and immediate memory skills, as well as assessment of the subjective state," Ana Adan from the University of Barcelona wrote in her report Cognitive Performance and Dehydration.


It's not just running out of water that's the problem, it's running low on glucose which is stored and used as energy in the human body.

Provost's distinguished research Professor Dr Peter Hancock points out every organ in the human body needs glucose to survive.

In the brain, he notes, glucose is a necessity for both lower order automatic functions and higher order executive functions.

The body expends greater energy — glucose — to cool the body down. Hot climates require the body to use more energy than when it's cooler.

So once glucose is being used to regulate body temperature, less glucose is available for higher order cognitive functions — such as making decisions.

Not only does dehydration and loss of glucose make it harder to think, it's also believed, it makes us actively avoid making decisions.

An article in Scientific American, cites the work of researchers from the University of Virginia and the University of Houston who gathered sales data for different types of lottery games in St Louis County for a full year, then looked for changes in sales patterns against each day's temperature.

Sales for scratch tickets - in which buyers need to choose between many different options - fell markedly with any increase in temperature. Sales for lotto tickets, which require fewer decisions from the buyer, were not affected.


Another study, also cited in Scientific American, suggests warm conditions may not just cause people to fail at complex decision-making — it may cause them to avoid making some decisions entirely.

In this study, participants were placed in either a warm or a cool room and asked to choose between two products: an innovative one and a traditional one.

Those in warm rooms, relative to those in cool rooms, were much more likely to choose the traditional product — apparently because they did not have the cognitive resources necessary to evaluate the new information about the innovative item.

In a more straightforward test, researchers asked participants to proofread an article while they were in either a warm (25C) or a cool (19C) room.

Those in warm rooms performed much worse than those in cool rooms, failing to pick up almost half of the spelling and grammatical errors — those in cool rooms missed only a quarter of the mistakes.

The results suggest even simple cognitive tasks can be adversely affected by excessive ambient warmth.

And, given the conditions, that's probably enough science to take in for the water cooler conversation.