Drunkard's Walk - Leonard Mlodinow [11]
We can never know for certain whether Maris was a far better player in 1961 than in any of the other years he played professional baseball or whether he was merely the beneficiary of good fortune. But detailed analyses of baseball and other sports by scientists as eminent as the late Stephen Jay Gould and the Nobel laureate E. M. Purcell show that coin-tossing models like the one I’ve described match very closely the actual performance of both players and teams, including their hot and cold streaks.20
When we look at extraordinary accomplishments in sports—or elsewhere—we should keep in mind that extraordinary events can happen without extraordinary causes. Random events often look like nonrandom events, and in interpreting human affairs we must take care not to confuse the two. Though it has taken many centuries, scientists have learned to look beyond apparent order and recognize the hidden randomness in both nature and everyday life. In this chapter I’ve presented a few glimpses of those workings. In the following chapters I shall consider the central ideas of randomness within their historical context and describe their relevance with the aim of offering a new perspective on our everyday surroundings and hence a better understanding of the connection between this fundamental aspect of nature and our own experience.
CHAPTER 2
The Laws of Truths and Half-Truths
LOOKING TO THE SKY on a clear, moonless night, the human eye can detect thousands of twinkling sources of light. Nestled among those haphazardly scattered stars are patterns. A lion here, a dipper there. The ability to detect patterns can be both a strength and a weakness. Isaac Newton pondered the patterns of falling objects and created a law of universal gravitation. Others have noted a spike in their athletic performance when they are wearing dirty socks and thenceforth have refused to wear clean ones. Among all the patterns of nature, how do we distinguish the meaningful ones? Drawing that distinction is an inherently practical enterprise. And so it might not astonish you to learn that, unlike geometry, which arose as a set of axioms, proofs, and theorems created by a culture of ponderous philosophers, the theory of randomness sprang from minds focused on spells and gambling, figures we might sooner imagine with dice or a potion in hand than a book or a scroll.
The theory of randomness is fundamentally a codification of common sense. But it is also a field of subtlety, a field in which great experts have been famously wrong and expert gamblers infamously correct. What it takes to understand randomness and overcome our misconceptions is both experience and a lot of careful thinking. And so we begin our tour with some of the basic laws of probability and the challenges involved in uncovering, understanding, and applying them. One of the classic explorations of people’s intuition about those laws was an experiment conducted by the pair who did so much to elucidate our misconceptions, Daniel Kahneman and Amos Tversky.1 Feel free to take part—and learn something about your own probabilistic intuition.
Imagine a woman named Linda, thirty-one years old, single, outspoken, and very bright. In college she majored in philosophy. While a student she was deeply concerned with discrimination and social justice and participated in antinuclear demonstrations. Tversky and Kahneman presented this description to a group of eighty-eight subjects and asked them to rank the following statements on a scale of 1 to 8 according to their probability, with 1 representing the most