Interview with Leonard Mlodinow (part 10)

ROBERTS What did you think of The Black Swan on the same topic?

MLODINOW It’s on the topic of how little things can cause big changes, you mean, and . . .

ROBERTS And how poorly we understand what really matters.

MLODINOW  I haven’t read the book from beginning to end so it’s hard to comment on that.

ROBERTS What about his previous book? There are similar ideas in the two books.

MLODINOW I didn’t really notice that book when I started writing Drunkard’s Walk; I wasn’t aware of the book. I had looked–in the library–gone through tons of books that seemed somehow related to randomness and somehow that one didn’t stand out to me. Sometime later it came out in paperback and it got very popular. Then I rediscovered it, and yes, I agree with a lot of what he says in that first book, but I still never read it from cover to cover. I’m not the type who feels compulsive about reading everything that’s been written on the subject that I’m writing on.

ROBERTS Yes. I always think of his book as being about these very long-tailed distributions–not only about that, but they play a large role–whereas you didn’t mention long-tailed distributions in your book.

MLODINOW Not explicitly, but I did talk about that idea and certainly the idea that not everything follows a normal distribution and how important it is to note that, for instance in Hollywood–Hollywood box office receipts. But I think The Black Swan was exclusively about that, so in that sense it was a different topic.

[For readers who don’t know what that is, if you’re talking about the probability of events occurring–let’s say you’re talking about the probability of a movie making a certain amount of money–there may be a mean amount of money that a movie makes or that a movie of that type makes. Then there will be fluctuations around it; some movies will make more, some movies will make less. The normal distribution is a distribution of the revenues that would follow a bell curve and the long-tailed distribution differs. One of the important respects that it differs in is that it has a lot more results that are far from the average that you would expect in a normal distribution. So if the average movie makes $1,000,000 or to be more realistic let’s say the average movie makes $50,000,000 and if it was normally distributed you would have, depending on the variance, but let’s just say you would have a certain number that make 40 or would make 60 and another small number would make 30 or 70 and you have a very small number indeed–probably practically zero–that would make $500,000,000. In Hollywood the way it really works is there are more that differ that far from the median than you would have if it were a normal distribution. That’s what they call a long-tailed distribution–the number of occurrences that are far from the average is much higher than you would expect with the normal distribution. — LM]

So that applies in many areas of life as well. I think that translated into what we were just talking about, it means that these little minor incidents can have major effects on you. It’s not all kind of pushed toward the mean effect, which is just going into my office and doing more physics.

ROBERTS Yes, I think that if you take the different things that have happened to you and you measured their effect, the effects will have a power-law distribution. A tiny number will have a huge effect and . . .


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