In hindsight bias, people who know the outcome of a situation believe the outcome should have been easy to predict in advance. Knowing the outcome, we reinterpret the situation in light of that outcome. Even when warned, we can’t de-interpret to empathize with someone who doesn’t know what we know.

Closely related is the illusion of transparency : We always know what we mean by our words, and so we expect others to know it too. Reading our own writing, the intended interpretation falls easily into place, guided by our knowledge of what we really meant. It’s hard to empathize with someone who must interpret blindly, guided only by the words.

June recommends a restaurant to Mark; Mark dines there and discovers (a) unimpressive food and mediocre service or (b) delicious food and impeccable service. Then Mark leaves the following message on June’s answering machine: “June, I just finished dinner at the restaurant you recommended, and I must say, it was marvelous, just marvelous.” Keysar (1994) presented a group of subjects with scenario (a), and 59% thought that Mark’s message was sarcastic and that Jane would perceive the sarcasm.1 Among other subjects, told scenario (b), only 3% thought that Jane would perceive Mark’s message as sarcastic. Keysar and Barr (2002) seem to indicate that an actual voice message was played back to the subjects.2 Keysar (1998) showed that if subjects were told that the restaurant was horrible but that Mark wanted to conceal his response, they believed June would not perceive sarcasm in the (same) message:3

They were just as likely to predict that she would perceive sarcasm when he attempted to conceal his negative experience as when he had a positive experience and was truly sincere. So participants took Mark’s communicative intention as transparent. It was as if they assumed that June would perceive whatever intention Mark wanted her to perceive.4

“The goose hangs high” is an archaic English idiom that has passed out of use in modern language. Keysar and Bly (1995) told one group of subjects that “the goose hangs high” meant that the future looks good; another group of subjects learned that “the goose hangs high” meant the future looks gloomy.5 Subjects were then asked which of these two meanings an uninformed listener would be more likely to attribute to the idiom. Each group thought that listeners would perceive the meaning presented as “standard.”6

Keysar and Henly (2002) tested the calibration of speakers: Would speakers underestimate, overestimate, or correctly estimate how often listeners understood them?7 Speakers were given ambiguous sentences (“The man is chasing a woman on a bicycle.”) and disambiguating pictures (a man running after a cycling woman). Speakers were then asked to utter the words in front of addressees, and asked to estimate how many addressees understood the intended meaning. Speakers thought that they were understood in 72% of cases and were actually understood in 61% of cases. When addressees did not understand, speakers thought they did in 46% of cases; when addressees did understand, speakers thought they did not in only 12% of cases.

Additional subjects who overheard the explanation showed no such bias, expecting listeners to understand in only 56% of cases.

As Keysar and Barr note, two days before Germany’s attack on Poland, Chamberlain sent a letter intended to make it clear that Britain would fight if any invasion occurred. The letter, phrased in polite diplomatese, was heard by Hitler as conciliatory—and the tanks rolled.

Be not too quick to blame those who misunderstand your perfectly clear sentences, spoken or written. Chances are, your words are more ambiguous than you think.