1) Most investors make mistakes in decisions about risk versus return due to specific cognitive weaknesses. These mistakes can cost investors real money over time. 2) Research has provided an understanding of these cognitive weaknesses, such as not being good at math, myopic loss aversion, and not properly accounting for the benefits of diversification. 3) Nudges and alternative presentations of investment information, such as broad framing and focusing on long-term goals, can help reduce problems like loss aversion and result in better investment decisions over the long run.