Sunday, December 20, 2009

The Expected Unexpected, a review of The Black Swan by Taleb

The Expected Unexpected - or, What can we learn from White Swans?

A review of The Black Swan, by Nassim Nicholas Taleb

Review by Todd I. Stark, 12/20/2009

Link to review on Amazon.

I came to this book expecting a clever but flawed argument for intellectual laziness or superficial thinking, another popular argument for "gut" or "intuition" or "Zen." Or perhaps a slick Gladwell-esque treatment of randomness. Perhaps a popularization of postmodernism or neo-pragmatism applied to financial markets, or a "Thriving on Chaos" (Tom Peters) for the 21st century.

This book is none of those things. Instead I found myself immersed in a very intriguing and deep intellectual journey into the roots of applied statistics and empirical science that had me thinking and taking notes prolifically. As readable as it is, this is not (or should not be) a quick read. Taleb is an erudite scholar but he uses his scholarship in the service of ideas rather than to accumulate impressive footnotes. His lectures are conversational but convey great weight.

I do find his tone somewhat arrogant in spots, oddly so. The half dozen or so people he finds interesting are worthy dinner companions, the rest of the world of intellegent mortals are pretty much fools who he chooses to stereotype and parody. Anyway, that's the impression I get. Contempt for audience usually works against an author. Still, very few modern authors can combine technical knowledge, originality, and readability the way Taleb can, and this to me kept me reading even when I imagined I was one of the many targets of the author's contempt.

Enough on style and impression, the content of this book is what makes it merit five stars. The core idea here is that we are creatures who quickly and easily sort things into categories and tell stories to make sense of them. Narration comes unbidden to us, but not skillful abstract thinking. This much of course we have heard before from the heuristics and biases school and behavioral economics.

Taleb's contribution is to point out a particularly broad implication of this principle, that our knowledge rapidly degrades when rare events are consequential. We explain them away and miss their importance. At the same time, we overestimate the impact of rare events for arbitrary reasons when they really have no consequence.

That would be of mostly academic interest except for one thing. The key to Taleb's overall argument is his claim that the impact of rare events is domain-specific. That means we can learn to distinguish domains where: (a) classical risk statistics apply ("Mediocristan") from (b) those where rare events and winner-take-all competitions dominate ("Extremistan").

In "Mediocristan" domains, classical decision theory in principle should help us (although Taleb seems to feel that these domains are few and far between among things we really care about). In "Extremistan," Taleb advises, we should take steps to protect ourselves from rare adverse events and use diverse aggressive risk taking to exploit rare positive events.

The idea here is that we are betting that something rare will eventually impact us in these domains, even though we can't know what specifically it will be. The point is that in domains where likelihood can't really be calculated, we should focus our efforts instead on the impact rather than guessing at the probability. Taleb doesn't make this argument lightly, he explains the limits in our predictive ability in an understandable way yet he also takes heed of technical details in his arguments.

"Extremistan" consists of all of the domains where scaling and nonlinear accumulations occur, or rapid deviations from small differences in initial conditions. In line with complexity theorists, Taleb finds these effects pretty much everywhere of interest to social scientists, economists, and people in general. He suggests that we might be able to use scalable non-linear maths to get a rough idea of what to expect in some domains, but that we need to remain careful of the illusion of mathematical predictive power.

Biological values like height and weight and average life expectancy are areas where the normal curve applies, and perhaps mean failure rate of parts in engineering. But when important things like money or fame or success can accumulate virtually without limit and often for arbitrary reasons like contagion, the assumptions of Gaussian distributions are just not relevant. At least that's how I understand Taleb's claim that the normal distribution is a great intellectal fraud: it is applied confidently to things where it has no place being applied.

With one strange but perhaps unavoidable exception, Taleb usually follows his own advice. He considers theories for storytelling purposes and explanation but doesn't take them seriously or depend on them for his argument. He does use storytelling quite a bit to make his point, even though his argument is largely about the unreliability of our stories. He seems to be saying that we automatically make sense of events through stories, so it takes a story to help us understand the argument against relying on storytelling.

I suppose there is a touch of the postmodernist skepticism of narratives in The Black Swan, but the possibility of having specific strategies for dealing differently with specific domains is an intriguing and welcome update to that tradition, bringing it perhaps more in line with the critical rationalism and conjectures and refutations of Karl Popper and the scientific skepticism of the classical pragmatists than with the modern cynics. Taleb is not rejecting theory entirely, but he certainly prefers direct experiment and aggressive risk taking (in strategic areas) to bland assumptions of predictable statistical likelihood and the reliability of knowledge.

For me this book ties together a lot of diverse ideas very nicely in an original and interesting way, and yet stays on target with its message.

Very impressive effort and a very worthwhile read.

No comments:

Post a Comment