Throughout history, humans have had to make decisions based on numerical comparisons of competing choices. Does this part of the forest yield more fruit than the other? What route leads to more or fewer violent encounters? Which shop has better deals? Although a computer with unlimited capacity could simply compute precise averages, humans often (by necessity) employ other methods. In a new set of experiments, Spitzer et al. asked people to decide which of two streams of numbers had a higher average value. Doing so, they provide new and exciting insights into the strategies humans employ to compare numerical magnitudes.