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Rock Breaks Scissors

Rock Breaks Scissors

A Practical Guide to Outguessing and Outwitting Almost Everybody
by William Poundstone 2014 320 pages
3.49
500+ ratings
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Key Takeaways

1. Humans Struggle with Randomness, Creating Predictable Patterns

All of us are constantly trying to predict the actions of others, while reserving some unpredictability for ourselves.

Inherent Predictability. Humans find it nearly impossible to behave unpredictably, especially in simple matters. This limitation stems from unconscious patterns influenced by training, emotions, and short memories. These patterns make human choices, even when intended to be random, susceptible to prediction.

Randomness Experiments. Studies show that when asked to generate random sequences, people tend to over-alternate between choices and avoid repetitions, creating patterns that deviate significantly from true randomness. This phenomenon is evident in various contexts, from generating digit sequences to playing games like rock, paper, scissors.

Implications for Outguessing. The predictability in human behavior provides a foundation for outguessing strategies. By recognizing these unconscious patterns, one can anticipate choices in various scenarios, including games, tests, and even financial decisions. The key lies in understanding that humans are more "mechanical" than they perceive themselves to be.

2. Exploit Predictable Irrationality in Games of Chance

The strategy for playing RPS depends on how skilled your opponent is.

Rock, Paper, Scissors Strategy. In rock, paper, scissors (RPS), novice players often favor rock, while women are more likely to throw scissors. Naive players also tend to avoid repeating the same throw more than twice in a row. These tendencies can be exploited to gain an advantage.

Advanced RPS Tactics. Expert RPS players use pattern recognition, emotional cues, and even trash talk to influence their opponents. Some plan their opening moves and adapt based on whether they win, lose, or tie. The goal is to anticipate the opponent's strategy and counter it effectively.

Poe's Purloined Letter. Edgar Allan Poe's detective, C. Auguste Dupin, solves crimes by understanding that people are predictable when trying not to be. This principle applies to RPS, where players often fall into predictable patterns despite their attempts to be random.

3. Multiple-Choice Tests Reveal Predictable Design Flaws

Test makers try to make it hard for someone who doesn’t know the material to guess the correct answers.

True-False Patterns. True-false tests often contain more "true" answers than "false" ones, and the sequence of correct answers tends to over-alternate. This information can be used to improve guessing accuracy.

Multiple-Choice Tendencies. In multiple-choice tests, the second answer (B) is often the correct choice in four-option questions, while the last answer (E) is favored in five-option questions. Additionally, "none of the above" and "all of the above" answers are disproportionately likely to be correct.

Strategic Guessing. By avoiding the previous correct choice and eliminating options based on clues within the question, test-takers can significantly improve their odds of guessing correctly. These strategies exploit the unconscious patterns of test makers.

4. Lottery Number Choices Reflect Human Bias, Not Randomness

State lotteries became successful only after New Jersey copied an idea from organized crime—letting bettors pick their own numbers.

Unpopular Numbers. Lottery bettors tend to avoid numbers ending in 0, 8, or 9, as well as those containing the "lucky" number 7. They also favor smaller digits and numbers that could be dates.

Ziemba's Research. William Ziemba found that the ten least played numbers in a standard pick-six lottery are 40, 39, 20, 30, 41, 38, 42, 46, 29, and 49. These numbers are about 15 to 30 percent less popular than average.

Contrarian Strategy. By selecting unpopular numbers, lottery players can increase their chances of winning a larger share of the jackpot. However, the odds of winning remain extremely low, and the strategy is primarily for those who enjoy playing the lottery as entertainment.

5. Anticipate Opponents' Moves in Sports by Recognizing Patterns

When you’re receiving, expect the serve to alternate.

Tennis Serve Patterns. Tennis players often over-alternate their serves, making it possible to anticipate the direction of the next serve. A serve to the right is more likely to be followed by a serve to the left.

Randomization Techniques. To avoid predictability, servers can use a heart-rate monitor or watch to generate random choices. The even or oddness of the last digit can determine the direction or type of serve.

Baseball and Football Strategies. In baseball, pitchers tend to over-alternate their pitches, making it possible for batters to anticipate the next pitch. In football, teams are more likely to switch between running and passing plays after an unsuccessful play.

6. Financial Data Often Contains Predictable Anomalies

The random, the arbitrary, and the made-up are all around us and sometimes take on great importance.

Benford's Law. Benford's Law states that in many real-life sets of numerical data, the leading digit is likely to be small. For example, about 30% of numbers start with 1, while only 4.6% start with 9. This law can be used to detect fraud.

Fabricated Numbers. People who make up numbers often unconsciously repeat themselves and favor certain digits. They also tend to avoid round numbers and create patterns that deviate from Benford's Law.

Applications in Fraud Detection. Digit analysis can be used to authenticate expenses, sales figures, tax returns, and election results. By recognizing the idiosyncrasies of invented numbers, investigators can identify potential fraud.

7. The Hot Hand Fallacy Distorts Perceptions of Performance

The semi- is the hardest part of that idea to accept.

The Hot Hand Illusion. The hot hand theory is the belief that a player who has made several successful shots in a row is more likely to make the next shot. However, research has shown that this belief is often an illusion.

Randomness Misconception. People tend to see patterns in random sequences, leading them to believe in the hot hand even when it doesn't exist. They also underestimate the likelihood of streaks in random data.

Implications for Decision Making. The hot hand fallacy can lead to poor decisions in sports, investments, and other areas. It's important to recognize that performance is often more random than it appears.

8. Crowd-Sourced Ratings Reflect Biases and Can Be Outguessed

We are all currently engaged in a Zenith experiment, and the stakes are our privacy, our wealth, and our very identities.

The Number 7 Bias. People asked to think of a number between 1 and 10 most often pick 7. This bias can distort crowd-sourced ratings, causing them to peak at around 7 out of 10.

Scale Limit Significance. Ratings at or near the scale limits (e.g., 0-star or 5-star) carry the most conviction. These ratings are more likely to reflect genuine opinions and experiences.

Implications for Decision Making. When evaluating crowd-sourced ratings, pay particular attention to the proportion of lowest and highest ratings. These extremes provide more valuable information than the average score.

9. Password Creation is Limited by Predictable Human Choices

The computer user believes that she has utter freedom to choose a password.

Common Password Patterns. Many people use easily guessable passwords, such as "password," "123456," and "qwerty." They also tend to follow predictable patterns when adding numbers, punctuation marks, and capitalization.

Mangled Passwords. Even prudent users favor the same patterns of obfuscation, such as adding "123" onto the end or alternating capitals and lowercase letters. This reduces the range of potential options and makes passwords easier to crack.

Creating Strong Passwords. To create a secure password, use a random string of characters. You can also convert a phrase or sentence to a password, but avoid using famous quotes.

10. Outguessing Requires Understanding Both Psychology and Statistics

The random, the arbitrary, and the made-up are all around us and sometimes take on great importance.

Combining Disciplines. Outguessing involves understanding both the psychology of human behavior and the statistics of random events. By combining these disciplines, one can develop effective strategies for predicting and influencing outcomes.

Applications in Various Fields. The principles of outguessing can be applied to a wide range of fields, including sports, finance, marketing, and security. The key is to recognize the predictable patterns in human choices and exploit them to one's advantage.

Ethical Considerations. While outguessing can be a powerful tool, it's important to use it ethically and responsibly. The goal should be to improve decision-making and create positive outcomes, not to manipulate or deceive others.

Last updated:

Review Summary

3.49 out of 5
Average of 500+ ratings from Goodreads and Amazon.

Rock Breaks Scissors offers practical strategies for outguessing others in various situations, from games to investments. Readers appreciate the blend of psychology, statistics, and real-world applications, finding it informative and entertaining. Some criticize the book's repetitiveness and dense mathematical content, while others praise its insights into human behavior and decision-making. The book's broad coverage of topics means not all chapters appeal equally to every reader. Overall, reviewers find it an interesting read that provides useful tips for improving one's odds in everyday scenarios.

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About the Author

William Poundstone is an accomplished non-fiction author with over ten books to his name. His work explores the intersection of science, psychology, and society, often focusing on the financial and social impacts of scientific ideas. Poundstone's writing has appeared in prestigious publications like The New York Times, Harvard Business Review, and The Economist. He has also made numerous media appearances, including on popular television shows. With a background in physics from MIT, Poundstone brings a scientific perspective to his work. His books have achieved commercial success, selling over half a million copies worldwide, with "Fortune's Formula" receiving particular acclaim as Amazon's top non-fiction pick in 2005.

Other books by William Poundstone

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