Some days you’re so sharp you could beat Stephen Hawking in pub trivia. The next you stumble over words like a pissed athlete at a hurdle. Stephen Pincock, biochemist and author of Get Smart! 100 Lifestyle Choices That Affect Your Brain Power, says our sharpness varies depending on a host of factors, and he analyses things that enhance mental prowess and those that dampen it. Here, our pick of the surprising ones.

Mnemonics
No, this has nothing to do with Keanu Reeves. It’s all about your memory. Organising the mess on your desk makes life easier when you’re trying to find an important document, and the same principle applies when it comes to organising your memory. One trick used for centuries to help people remember things is the mnemonic (pronounced “nuhmonic”): a poem, word, sound or movement that creates easy connections to help organise related information. Remember that one from your piano-playing days, “Every Good Boy Deserves Fruit”? It’s based on the idea that it’s easier to remember meaningful information than to recall random details. Try this phrase for recalling the planets in order of distance from the sun: My Very Easy Method: Just Set Up Nine Planets = Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto. Or “Brass” for how to shoot a rifle (hey, you never know): Breathe, Relax, Aim, Sight, Squeeze. (Even saying “mnemonic” should make you sound more intelligent.)

Listening to music
New mums may rush out and buy classical music to encourage a clever child, but new studies suggest they may as well crank up Beyoncé in the nursery. In the early 90s, the idea that listening to Mozart boosted intelligence gained attention after researchers found that 26 college undergraduates improved their ability to mentally manipulate objects in a three-dimensional space after listening to a 10-minute Mozart sonata. Unfortunately for sales of classical CDs, repeat studies have failed to support these results. In fact, one study, published in the Annals of the New York Academy of Sciences found that the spatial abilities of 10 and 11 year olds were improved when they listened to pop music, but not when they were played Mozart. If 100 All-Time Classical Greats is your favourite download, by all means crank it. But the evidence is showing that listening to any music – yes, even Cliff Richard – can boost your brain power.

Gardening
If you want a sharp brain, cultivate green fingers. Australian researchers followed nearly 3000 people over the age of 60 for 16 years in the “Dubbo Study” – a longitudinal study of healthy ageing in Australian senior citizens conducted by universities in NSW and Victoria. They found that daily gardening reduced their risk of dementia by 36 per cent. The potential benefits of gardening are easy to imagine: exercise, stress relief and a creative outlet, all of which are known to have positive mental impacts. Researchers found that getting your hands dirty outdoors even just once a week keeps you mentally fit, so pitch in with weeding the next time you visit your folks, or just show your basil plant some love.

Leaving work early
It’s 4.45 on a Friday arvo. You’ve worked hard all week, the sun is still shining and escape is whispering your name. Your colleagues may be staring determinedly at their computers, lingering over an “urgent” report due in on Monday morning, but you grab your bag and run. Maybe you’ll earn a black mark in your boss’s book, but studies show that by doing this you’re actually protecting your mental facilities (good luck telling your boss that, though). Research published in the American Journal of Epidemiology found that people who worked more than 55 hours a week had noticeably lower scores in memory, attention and speed of information processing tests than those who called it quits after 40 hours. The authors of the study also found that the scale of decline seen in the overworked employees was similar in magnitude to that of smoking – a known risk factor for dementia.

Iron deficiency
Some 30 per cent of the world’s population is anaemic, approximately half of which is caused by iron deficiency. As well as an impaired immune response and lower physical endurance, scoring too low in this mineral can cause noticeable behavioural changes, including reduced attention span, lower emotional responsiveness and poor scores on tests of intelligence. A study reported in the American Journal of Clinical Nutrition showed that women who took iron supplements for 16 weeks significantly improved their attention, short and long-term memory, and their performance on cognitive tasks, even though many were not considered to be anaemic when the study began. Check with your doctor before taking iron supplements, but make sure you fill up on iron-fortified foods and beans if you don’t eat meat.

Early exposure to TV
OK, so there’s not much you can do about this one, but if you’re planning to go forth and multiply, take heed. In a 2005 study in the Archives of Pediatrics and Adolescent Medicine, researchers investigated how watching television affected the intellectual abilities of more than 5000 children. They found that for each hour of the idiot box watched before age three, kids did progressively worse on tests of reading and memory. The impact was strong enough for the researchers to recommend that children under two should not watch any TV. Good luck enforcing that rule when the Erky Perky theme song comes on.

This is an edited extract from Get Smart! 100 Lifestyle Choices That Affect Your Brain Power by biochemist Stephen Pincock