Rock Breaks Scissors | William Poundstone

Summary of: Rock Breaks Scissors: A Practical Guide to Outguessing and Outwitting Almost Everybody
By: William Poundstone

Uncovering Patterns in Human Behavior

This book explores the concept of identifying unconscious patterns in human behavior to make more accurate predictions. It highlights how you can apply this skill to win at games like “Rock, Paper, Scissors” and even multiple choice tests. The idea is that people tend to avoid clusters of similar moves, which means that predicting what they will do becomes easier. The same applies to test makers, who tend to have a bias towards true answers for their convenience. This presents a chance for test-takers to make educated guesses with over a 50% chance of being right. The trick is to answer the questions you are sure of first, then look for patterns within the surrounding answers for the ones you left blank. If two adjacent answers are the same, for instance, and the blank space requires a true or false answer, then the opposite choice to those two may be more accurate. Conversely, if the two adjacent answers differ, true is more often the right answer to guess. This book equips readers with invaluable insights for understanding human behavior and acting with a level of anticipation.

Maximizing Stock-Market Earnings

Many investors make the mistake of buying stocks when prices rise and selling when they fall. However, stock-market averages vary widely over the years because most investors chase perceived hot hands and fail to analyze long-term buy-and-sell patterns. To make sound investments, you can profit from other people’s predictability and do the opposite – buy when the market’s PE ratio approaches historical lows and sell when it climbs toward high levels. Instead of focusing on the current PE ratio, look at a long-term indicator like Yale economist Robert Shiller’s Cyclically Adjusted PE ratio that divides the latest S&P 500 ratio by the average earnings of the indexed companies for the past decade. You can also maximize earnings with a trailing stop order, which involves selling a stock when its price drops a specified percentage from its high, and reinvesting in fixed-income instruments. By adopting these strategies, you can make significantly more money in the stock market than the average investor.

The Power of Randomness in Strategy

To outsmart your opponents, it is not enough to predict their moves; you also need to make your moves unpredictable. The key is to incorporate randomness into your strategy. Tennis players, for example, can randomize their serves with the help of nonhuman aids, such as a wristband heart-rate monitor. By choosing a direction based on whether the number displayed on the monitor is odd or even, players can make their serves unpredictable and prevent their opponents from predicting their moves. This strategy applies to many other areas of life, as any human action that is not random is to some degree predictable. Therefore, incorporating randomness into our decision-making process can improve our chances of success. Letting go of the belief in the gambler’s fallacy, which assumes that chance outcomes that haven’t occurred in the recent past are more likely to occur in the near future, is key. By embracing randomness, we can become more unpredictable and enhance our performance.

Secure Passwords

When choosing a password, it’s essential to be unpredictable. Many people prefer easy-to-remember passwords rather than secure ones. However, it makes it easy for criminals to guess common passwords. Identity thieves can also use software that tries various dictionary words, names, nicknames, and pet names. To choose a safe password, choose one that’s too complex to remember and write it down. Use sites like for truly randomized letters and numbers. Be cautious of website security questions, which can aid users who forget their passwords. Make sure not to use easily guessable answers, or the thief wins an identity they can sell.

Final Recap

In conclusion, ‘Rock Breaks Scissors’ offers enlightening insights into the world of prediction and how to leverage it to outguess your opponents. Discover the secrets behind how our brain’s pattern-recognition works and how this can be exploited in a wide range of scenarios. The summary consolidates the importance of understanding patterns in human behavior and applying this knowledge to improve performance in various aspects of life, from business to personal choices. By learning and mastering these patterns, you gain a competitive edge that could prove invaluable in numerous situations. So grab the opportunity and expand your strategic arsenal with these predictive tools.


Prepare to elevate your strategic gamesmanship with the book summary of ‘Rock Breaks Scissors’ by William Poundstone. This engaging piece explores the fascinating world of predicting human actions and exploiting their unconscious patterns. Unearth the intriguing predictability in human choices concerning randomness, useful in various real-life situations such as sports, making sales, stock market investments, and even securing your passwords. The book highlights the importance of anticipating your opponents’ moves and, at the same time, effectively concealing your own.

Want to read the full book summary?