How likely is ‘likely’?

Episode Summary

Executive Summary: This episode examines how words used to express probability in news, government, and intelligence reporting often mean different things to different people. Using Adam Kucharski’s quiz of 5,000+ respondents, the show shows that some terms are widely understood, but others—especially “realistic possibility”—are highly ambiguous, creating risks for public communication and accountability.

Main Topics: Why probability words matter (Priority: 5/5): The episode opens by showing how everyday and news language uses words like likely, possible, and probable to communicate risk, but listeners may not interpret them consistently. Historical ambiguity in intelligence language (Priority: 5/5): A 1951 CIA example involving Sherman Kent shows that even experts and colleagues assigned very different numerical meanings to the same phrase, prompting concern about unclear risk communication. The probability yardstick (Priority: 4/5): The episode explains efforts, especially in UK intelligence, to standardize verbal probability terms by mapping them to numerical ranges so that phrases like “highly likely” or “realistic possibility” have agreed meanings. Results from Adam Kucharski’s quiz (Priority: 5/5): A large public quiz tested how people interpret probability phrases and compare them side by side, revealing which terms are stable and which are highly variable. Ambiguous terms and public risk communication (Priority: 5/5): The discussion highlights that phrases such as “realistic possibility,” “likely,” and “probable” can be interpreted very differently, which is problematic in contexts like pandemics, war, and climate change. Recommendations for clearer communication (Priority: 4/5): Kucharski argues that risk communicators should ensure their intended meaning matches what audiences hear, and should avoid hiding behind vague language to evade accountability.

Key Arguments: Verbal probability terms are often ambiguous and do not reliably convey the same level of risk to all listeners. Standardizing terms with a probability yardstick can improve clarity in intelligence and government communication. Public understanding varies widely, especially for phrases like “realistic possibility,” which can be interpreted anywhere from low probability to near certainty. Some phrases are relatively stable and widely understood, such as “will happen,” “almost certain,” and “almost no chance.” Education and nationality produced only small differences in responses; the main issue is the inherent ambiguity of the language itself. Risk communicators should use explicit numerical judgments where possible and ensure the speaker’s intended meaning matches the audience’s interpretation.

Data Points: Quiz participants: More than 5,000 - Number of people who took Adam Kucharski’s probability quiz Probability of “highly likely”: 80% to 90% - UK intelligence probability yardstick mapping Probability of “realistic possibility”: 40% to 50% - UK intelligence probability yardstick mapping Sherman Kent’s estimate of “serious possibility”: About 65% - Kent’s interpretation of a CIA report phrase in 1951 Average for “about even”: About 50% - Most consistent phrase in the quiz “Will happen” interpretation: 100% - Most respondents treated this as certainty “Almost certain” interpretation: Around 95% - Common respondent interpretation “Almost no chance” interpretation: 1% to 5% - Common respondent interpretation “Remote chance” interpretation: 1% to 10% - Common respondent interpretation “Highly unlikely” interpretation: 1% to 10% - Common respondent interpretation “Realistic possibility” range: 10% to near certainty - Most variable phrase in the quiz Average for “realistic possibility”: Just over 50% - Mean response in the quiz “Probable” and “likely” ranges: Around 50% to 100% - Respondent interpretations of these terms Average for “probable” and “likely”: Just under 75% - Mean response in the quiz

Pivotal Quotes: "“What did you mean by serious possibility?”" — Chairman: The chairman challenges Sherman Kent’s wording in the 1951 CIA example "“I thought about 65%.”" — Sherman Kent: Kent explains what he meant by “serious possibility” "“The most variable phrase was realistic possibility.”" — Adam Kucharski: Kucharski summarizes the quiz result showing extreme ambiguity

Implications: Listeners should be cautious when hearing vague risk language in media or official statements. For journalists, scientists, and policymakers, clearer numerical communication can reduce misunderstanding and improve accountability.