He named this body of water “Lake Disappointment.” Hann felt let down by the lake because his prior experience in geography pointed toward it being a freshwater lake. In human communication, we continuously repair mismatches between what we think is true and what we think others think is true. When Frank Hann realized the lake had salt water in it, his brain did exactly what it had evolved to do. But by choosing the name “Lake Disappointment,” he wasn’t just correcting a prediction error, he was leaving a monument to it.