There are three main potential explanations, says Scholey. In March 2000, Japanese researchers showed that brain activity in the hippocampus, an area important for memory, increases while people chew - but it is not clear why.
Recent research has also found that insulin receptors in the hippocampus may be involved in memory. "Insulin mops up glucose in the bloodstream and chewing causes the release of insulin, because the body is expecting food. If insulin receptors in the brain are involved in memory, we may have an insulin-mediated mechanism explaining our findings - but that is very, very speculative," Scholey says.
But there could be a simpler answer. "One interesting thing we saw in our study was that chewing increased heart rate. Anything that improves delivery of things like oxygen in the brain, such as an increased heart rate, is a potential cognitive enhancer to some degree," he says.