Once again, politicians ask experts and come out none the wiser

Today in the Commons, MPS have to decide whether to answer Boris Johnson’s plea, and vote to impose a lockdown on England. It’s a tough choice. So yesterday, to help everyone make up their minds, a group of MPS interrogated the Government’s top scientific advisers, Prof Chris Whitty, the Chief Medical Officer for England, and Sir Patrick Vallance, the Government’s Chief Scientific Adviser.

Unfortunately, the interrogation wasn’t easy to follow because of this basic problem: politicians are very good communicators but don’t necessarily know a lot about science, while scientists know lots about science but aren’t necessarily very good communicators.

As a result, the two sides seemed to be struggling to understand each other – while the viewer at home struggled to understand either. Naturally the MPS wanted to ask about the alarming series of graphs shown during the Prime Minister’s news conference on Saturday night. These exchanges, however, proved both lengthy and gruellingly repetitive.

On one side was a succession of MPS endlessly asking how likely it was that their terrifying predictions might come true. On the other side were the scientists, endlessly trying to explain to MPS that the predictions weren’t predictions, they were scenarios. Then the MPS would struggle to grasp the difference between a prediction and a scenario – while the scientists, in turn, would struggle to explain it to them.

At times it felt like watching an English tourist with no Spanish ask directions from a Spaniard with no English. Half way through, Chris Clarkson (Con, Heywood & Middleton) asked the scientists to tell him the rate of false positives (that is, when people who don’t have Covid nonetheless test positive for it).

Here’s a sample reply from Prof Whitty: “The point I’d make as an epidemiologist is that the key metric is actually not the sensitivity of specificity, although that’s important, it’s the positive and negative predictive value, which varies by prevalence at a point in time, and those will become more accurate as the prevalence rates go up, so that the risk of a false positive is higher when the rates are actually lower.”

Mr Clarkson didn’t ask Prof Whitty to clarify. Which could mean that he understood the answer. Although it could equally mean that by this point his head was spinning so fast he couldn’t even remember his original question.

Still, it seems that scientists and politicians do at least have one thing in common. They hate to give a straight yes or no answer.

Greg Clark (Con, Tunbridge Wells) asked Prof Whitty whether he believed the lockdown could be lifted on Dec 2.

“I think that the aim of this,” replied Prof Whitty, “is to get the rates down far enough that it’s a realistic possibility to move into a different state of play at that point in time.”

Magnificently non-committal. Now he was speaking their language.