It's happened to all of us. Someone asks you a simple question, you reach for the answer. It's there, you know it's there but, all of a sudden... nothing. Panic sets in. Your pulse quickens. Your heart starts thumping like a snare drum.

Mental blanks can be uncomfortable, disturbing, embarrassing. More often than not though, we shrug them off and move on. For politicians, forgetting the answer to a question (or not knowing the correct answer) is an occupational hazard. At its worst, it can be a career killer.

Journalists know that tripping up a pollie - known as a "gotcha" in the trade - is one of the surest ways to score a headline.

Defence Minister Kevin Andrews was the latest pollie to fall victim to the gotcha in an interview with the ABC's 7.30 program on Tuesday night.

Andrews was asked repeatedly by host Leigh Sales to identify the head of the Islamic State terror group and on all four occasions could not come up with the answer. Given Australia has just committed 330 extra troops to fight Islamic State in Iraq, it was a bad look.

Instead of fessing up, Andrews obfuscated by saying that the group's leadership was complex and shifting. He's hardly the first to try to wriggle out of a tricky interview in this way.

Earlier this year, shadow treasurer Chris Bowen was unable to name the tax-free threshold rate in a television interview with Alan Jones.

"I chose not to answer the question," Bowen insisted a day later. "I didn't see it being as relevant to the conversation at hand."

Former Labor powerbroker Graham Richardson, who has been a close friend of Bowen's for years, accused him of making the problem worse with this response.

Bowen didn't lose his job and neither will Andrews.

Senator Ricky Muir has established a more confident media presence after struggling to define "balance of power" in his first television interview. And Annastacia Palaszczuk even scored an upset victory in the Queensland election a week after being unable to name the rate of the GST.

Not every one is so lucky. Bob Hawke sacked his treasurer John Kerin in 1991 after he was unable to say what GOS - Gross Operating Surplus - stood for.

"Every minister will have examples such as that in the back of their mind," says Sean Kelly, a former media adviser to former prime ministers Kevin Rudd and Julia Gillard.

"They don't want this to be the single mistake that blows up and ruins their career.

"Any prime minister or treasurer who goes out the day after the budget not knowing what a litre of milk or petrol costs is signing a death warrant."

Kelly's advice to politicians who freeze under the spotlight is simple: don't fudge.

"Own up to it immediately - say I've forgotten and I will come back to you," he advises. "I reckon the public understands that politicians are human and forget things like everyone else.

Sue Cato, one of the nation's top corporate communications advisers agrees. "You're not going to get away with not knowing the answer but if you front up to having a memory lapse you can help control the size and colour of the bruise."

Responding with a sense of humour and grace - rather than indignation - will help as well, Cato says.

That said, Kelly has sympathy for politicians who try to avoid participating in pop quizzes. Doing so simply encourages gotcha journalism, he says, where journalists focus on embarrassing politicians rather than informing the public.

"Pop quizzes are a very superficial way of assessing a politician's capacity; they don't necessarily reflect how competent a minister is or how good they are at solving policy problems," he says. "They often just show whether they have read briefing notes prepared by their media adviser.

"As long as the mistake is not seen as reflective of a deeper problem, the wrong answer in a pop quiz probably won't do much damage."

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