Scientific evidence has been produced to confirm a long-derided advertising slogan which claimed that chewing gum speeds up thinking and alertness. Newly published research shows that reaction times are up to 10 per cent faster while chewing gum, and that as many as eight different areas of the brain are affected.

One theory is that chewing increases arousal and leads to temporary improvements in blood flow to the brain, which may help to explain its widespread use among successful football managers, most notably Alex Ferguson.

A new study, being reported in the journal Brain and Cognition, says volunteers carried out tests while chewing or not chewing gum. The gum used was flavourless to avoid distractions. The brains of the men and women were also scanned with functional magnetic resonance imaging (fMRI) to see which areas were active.

The 30-minute tests involved volunteers pressing a button with their right or left thumb according to the direction of an arrow on a screen in front of them. One test was more complicated than the other. During both tests, alertness and reaction times were measured.

Results show that alertness and reaction times improved while chewing gum. Men and women who were not chewing took 545 milliseconds to react, compared with 493 milliseconds among the chewers. The scan results show that the brain regions most active during chewing were those involved with movement and attention.

"Our results suggest that chewing induced an increase in the arousal level and alertness in addition to an effect on motor control and, as a consequence, these effects could lead to improvements in cognitive performance," say the researchers from the National Institute of Radiological Sciences in Japan, and other centres.

Just how chewing could have such a profound effect is not clear, but there are theories. In one small experiment, chewing a piece of gum for 20 minutes led to an increased heart rate, and one suggestion is that this forces more oxygen and nutrients to the brain. Another is that chewing leads to the production of higher levels of insulin, which stimulates areas of the brain concerned with memory and alertness.

Professor Andy Smith of Cardiff University, a leading health-related behavioural specialist who has investigated chewing gum and behaviour, said: "It is an interesting study. The improvement in reaction time they found is highly significant. It may be that the more complicated the task, the greater the effect on reaction times. We don't really know how chewing could have such effects. Is it simply the stress-relieving effect of the rhythmic action of chewing, like chanting or a squeeze ball, or is something more fundamental going on?

"The effects of chewing on reaction time are profound. Perhaps football managers arrived at the idea of chewing gum by accident, but they seem to be on the right track."