EXAM candidates wanting to boost their performance should take a glucose drink before or after a revision session, drink ginseng tea on the morning of the test, and saunter into the exam itself armed with a stick or two of chewing gum.

But they should leave alcohol and aromatherapy until the ordeal is over. Alcohol makes people over-optimistic about their performance, which may explain why they make more errors. And lavender oil, commonly believed to have sedative properties, does in fact adversely affect attention and memory.

These are among the findings presented by researchers to this week’s annual conference of the British Psychological Society in Blackpool.

Researchers from Lancaster University and the University of Western Australia gave drinks containing glucose or a placebo to 60 young volunteers. They were then shown a list of 20 words which they were asked to recall half an hour later, and again the next day.

Those who drank the glucose could remember 15 words, while those who drank the placebo could remember only 10. It did not matter whether the volunteers received the glucose just before or just after they viewed the list. The improvements were almost the same. This suggests the glucose improves the way that memories are subsequently formed.

“Students may benefit from taking glucose before or shortly after their lectures and during their revision,” Dr Sandra Sunram-Lea of Lancaster University said.

The effects of herbs and other substances on thinking, memory and mood were tested by researchers at the Human Cognitive Neuroscience Unit at the University of Northumbria, the AstraZeneca UK Clinical Research Group in Edinburgh and Cognitive Research Ltd, Reading.

They looked at the effects of ginseng on electrical activity in the brain and concluded that ginseng may improve thinking skills. Chewing gum significantly improved memory, and taking Spanish sage (salvia lavandufolia) improved both mood and thinking skills.