Washington: Researchers have discovered that stress is not all bad, after all -- some bit of it can push one to a level of heightened alertness and better performance, a new study claims.

"You always think about stress as a really bad thing, but it's not," said Daniela Kaufer, associate professor of integrative biology at the University of California-Berkeley. "Some amounts of stress are good to push you just to the level of optimal alertness, behavioural and cognitive performance."

New research by Kaufer and UC-Berkeley post-doctoral fellow Elizabeth Kirby has uncovered exactly how acute stress -- short-lived, not chronic -- primes the brain for improved performance.

In studies on rats, they found that significant, but brief stressful events caused stem cells in their brains to proliferate into new nerve cells that, when mature two weeks later, improved the rats' mental performance, reports media.

"I think intermittent stressful events are probably what keep the brain more alert, and you perform better when you are alert," she said.