This document introduces heuristics, which are simple decision-making strategies or rules of thumb that ignore part of the available information. The author discusses research showing that in situations of uncertainty, heuristics can predict customer behavior as well or better than complex statistical models that take all available data into account. A simple heuristic based on the recency of a customer's last purchase outperformed a complex model in predicting which customers would make future purchases. The author argues that heuristics work well under uncertainty because they avoid overfitting past data and have lower variance than complex models. Under uncertainty about the future, heuristics that simplify by ignoring some information can make more accurate predictions than approaches that optimize based on all past data.