a realistic possibility

thetimes.com How likely is ‘almost certainly’? Tom Whipple

There is a realistic possibility that your idea of “realistic possibility” is very different from everyone else’s. It is probable, or even likely, that my understanding of what the words “could happen” mean diverges markedly from yours.

And that’s before we get into whether saying something is “likely” is a stronger statement than saying it is “probable”.

This is the conclusion of a survey about the “weasel words” we use to denote the chance of something happening without putting a number on it.

For an area of linguistics in which misunderstandings have contributed to at least one military disaster, the new research finds that when we talk about likelihoods, a lot of meaning is — wittingly or not — almost certain to be lost between speaker and recipient. “Almost certain”, for instance, is interpreted as denoting a probability of anywhere between 80 per cent and 100 per cent.

Adam Kucharski, an epidemiologist, carried out the investigation in part because of his experience communicating risk during the pandemic. In particular, when called on to assess a new Covid variant in 2021, he said: “Sage colleagues and I concluded early on that it was a ‘realistic possibility’ that the Delta variant was much more transmissible.”

They chose those words deliberately. The UK, like many organisations, now has official guidance on what phrases such as “realistic possibility” mean — in this case equating to between 40 per cent and 50 per cent.

But do general readers understand it? Kucharski, author of Proof: The Uncertain Science of Certainty, decided to conduct a poll of more than 5,000 people, asking what they thought phrases meant.

Some words, such as “better than even” and “almost certain” were pretty well understood. Others were not at all.

Kucharski also found that different groups, and countries, saw phrases differently. People from America were consistently more optimistic — meaning they assumed a given phrase denoted a slightly higher probability. People who spent more time in education, conversely, were consistently more pessimistic.

The phrase Kucharski used for the Delta variant, “realistic possibility”, was the least well defined of all: interpretations of probability ranged from 10 per cent to 100 per cent. “I now realise that wider audiences may have heard something very different,” he said.

It was in fact, he concluded, the “weaseliest of words” — a nod to the man who first identified such terms as problematic in the 1950s. After the CIA warned of a “serious possibility” that the Soviet Union would invade Yugoslavia, the analyst Sherman Kent wondered whether everyone was hearing the same meaning when they heard the same words. They weren’t: estimates for the probability ranged from 20 per cent to 80 per cent. Portrait of Sherman Kent, a Yale history professor and pioneer of intelligence analysis.

Sherman Kent

CENTRAL INTELLIGENCE AGENCY

He called for a complete reform of advice, arguing that “weasel words” like “could” and “suggest” were “expressions with sound but upon reflection almost without meaning”.

“He said these words were used when people just didn’t want to get pinned down,” Kucharski said.

The agency was soon to get a lesson in why pinning down meaning was important. After assuming the presidency, John F Kennedy was presented with an assessment of a planned invasion of Cuba. The joint chiefs of staff told him it had a “fair chance” of success. He later said he had interpreted that as a good sign, and went ahead with the plan.

The joint chiefs later said they meant “3 to 1 against”. The result was the Bay of Pigs fiasco.