New York, Mar 6 (IANS): Caffeine increases the ability to focus and solve problem, but it doesn't stimulate creativity, according to a new study.

While the cognitive benefits of caffeine -- increased alertness, improved vigilance, enhanced focus and improved motor performance -- are well established, the stimulant's affect on creativity is less known.

"In Western cultures, caffeine is stereotypically associated with creative occupations and lifestyles, from writers and their coffee to programmers and their energy drinks, and there's more than a kernel of truth to these stereotypes," said study researcher Darya Zabelina, Assistant Professor at University of Arkansas in the US.

In the study, published in the journal Consciousness and Cognition, the researchers differentiates "convergent" from "divergent" thinking. The former is defined as seeking a specific solution to a problem, for example, the "correct" answer.

The latter is characterised by idea generation where a large set of apt, novel or interesting responses would be suitable.

Caffeine was shown to improve convergent thinking in the study, while consuming it had no significant impact on divergent thinking.

For the study, 80 volunteers were randomly given either a 200mg caffeine pill, equivalent to one strong cup of coffee, or a placebo.

They were then tested on standard measures of convergent and divergent thinking, working memory and mood.

In addition to the results on creativity, caffeine did not significantly affect working memory, but test subjects who took it did report feeling less sad.

"The 200mg enhanced problem solving significantly, but had no effect on creative thinking, it also didn't make it worse, so keep drinking your coffee; it won't interfere with these abilities.

The University of Arkansas is a public land-grant, research university in the US.