Drinking coffee can cause tip-of-the-tongue moments when the brain struggles to retrieve information, according to a study.

Caffeine, widely held to make people more alert, can make the mind go blank or struggle to switch between trains of thought.

It can help the brain process information rapidly but interferes once the brain tries to switch between subjects, researchers claim.

Volunteers were split into two groups, with one given 200 milligrams of caffeine -- the equivalent of two cups of coffee. They then answered 100 questions after reading 10 "priming words" with between two and eight of the words sounding similar to the answer.

Caffeine appeared to help participants find the correct answers when primed with many similar sounding words. However, when there were more unrelated priming words, they suffered more tip-of-the-tongue moments than those who had not had coffee.

The study, by researchers in Italy, is published in Behavioral Neuroscience.