On a related note: I suspect that humans cannot "guesstimate" numbers greater than 20 by sight. I have tried this experiment on myself, friends and relatives an

On a related note: I suspect that humans cannot "guesstimate" numbers greater than 20 by sight. I have tried this experiment on myself, friends and relatives and so far no one has succeeded. Take a glance at the next longish queue and try to guess, are there greater than 50 people or fewer than that? The first guess is usually wrong. This is similar to the picture of the logjam in the article. Somehow, we know abstractly to count, have representations for numbers, and algorithms for arithmetic, but at a gut level, our instinct for numbers is not very spot-on.