Mr Spock is not as logical as he’d like to think

8th July, 2021

Mr Spock, Star Trek’s pointy-eared, nimble-eyebrowed Vulcan, is a beloved figure, especially as portrayed by the late Leonard Nimoy. He is a cultural touchstone for superior rationality. There’s just one problem: Spock is actually terrible at logic.

As Julia Galef explains in her new book on how to make better decisions, The Scout Mindset, Spock turns out to be highly illogical in more than one way. The most obvious is that Spock’s model of other minds is badly flawed.

For example, in an early episode, “The Galileo Seven”, Spock and his subordinates have crashed a small ship and face hostile aliens who kill one crew member. Spock decides to deter any further attacks by firing warning shots. The aliens respond not by retreating in fear, but by attacking in anger, killing another of the crew.

“Most illogical reaction,” comments Spock. “[When] we demonstrated our superior weapons, they should have fled . . . I’m not responsible for their unpredictability.”

“They were perfectly predictable,” rages Dr McCoy, “to anyone with feeling.”

Spock is not being rational here, but the problem is not that he lacks feeling, rather that he lacks the capacity to learn from experience. He should have noticed aggression is often met with aggression.

To a fan of rational inquiry, which Galef is, Spock’s portrayal is an infuriating smear. Spock, she says, is a “Straw Vulcan” — a caricature of rationality designed to make rationality look foolish. Perhaps so, but the reason that I winced when I rewatched the episode is not because he was a caricature, but because his error looked all too familiar.

“Rationality is an assumption I make about other people . . . Rationality is the best predictive assumption available . . . If irrational behaviour is random, its effects may average out.”

That’s not Spock. It’s David Friedman in Hidden Order: The Economics of Everyday Life offering a distinctly Spock-like justification for assuming rationality in others: you might as well because rationality gives a predictive toehold, while irrational behaviour is hopelessly unpredictable.

I recommend Hidden Order as a superb introduction to economic thinking. However, it shares the weakness of mainstream economic approaches in the 1990s, when the book was published. The most obvious rejoinder to Friedman’s argument is McCoy’s: “irrational” does not mean “unpredictable”. People may be irrational in perfectly predictable ways, and indeed they are. (Not for nothing is a popular behavioural science book titled Predictably Irrational.)

There is a value in assuming rational behaviour. It is simple to describe and analyse, and it has predictive power. As a tractable, one-size-fits-all model of human behaviour, it may be as good as we are going to get. But in specific cases it may help to bring in perspectives from psychology, from experimental data, or simply from judgment and experience.

“I’ve always said that if you want one unifying theory of economic behaviour, you won’t do better than the neoclassical [rational] model,” Richard Thaler told me back in 2014, a few years before winning the Nobel Memorial Prize for his work on more psychologically realistic economics. He added that while the rational-choice model might be the best available unified theory, it was also “not particularly good at describing actual decision-making”.

Spock, then, may not be a Straw Vulcan after all, but a dramatic portrayal of the mistakes economists have tended to make in insisting that we must assume everyone is rational.

There is another way that we economists might learn from observing Spock’s mistakes. He is a truly terrible forecaster. Galef, rather delightfully, has gone through the full catalogue of Star Trek, finding every occurrence she could of Spock making a prediction.

“[There’s] only a very slight chance [this plan] would work,” Spock tells Captain James T Kirk at one stage. The plan works. “Intercepting all three ships is an impossibility,” he warns Kirk during another adventure. Kirk intercepts all three ships. The chance of a daring escape? “Difficult to be precise, Captain. I should say approximately 7,824.7 to one.” They escape.

Other fictional characters have made similar remarks. C-3PO (Star Wars) and Dr Strange (Marvel) spring to mind. We cannot blame them; blame, instead, the writers.

Yet this sort of overconfident nonsense is common in real-world punditry. We seem to have an unslakable thirst for knowledge about the future. Sadly, knowledge about the future is not easy to acquire, so we satisfy ourselves with the pretence of knowledge.

If you can’t be accurate, at least sound self-assured. Spock does, every time. “My choice will be a logical one,” he upbraids a subordinate, shortly before making another fatal error, “arrived at through logical means.”

Well said. But his record is not so good. According to Galef’s tally, when Spock says something is “impossible” it happens 83 per cent of the time, and when he gives something more than a 99.5 per cent chance, it happens just 17 per cent of the time. (He does OK with his forecasts of “likely”.) This makes him a reliably contrarian indicator, as Kirk seems to have realised — just ask Spock for his opinion, then do the opposite.

Failing that, if you want to become a better forecaster, do what Galef did: look back at old forecasts and keep score.

Written for and first published in the Financial Times on 11 June 2021.

The paperback of “How To Make The World Add Up” is now out. US title: “The Data Detective”.

“One of the most wonderful collections of stories that I have read in a long time… fascinating.”- Steve Levitt (Freakonomics)

“If you aren’t in love with stats before reading this book, you will be by the time you’re done.”- Caroline Criado Perez (Invisible Women)

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