On Crimes and Cognitive Biases

In my previous post, I touched on how we often prefer a smaller reward now than a larger one later (depending on the size of the rewards and the interval between them of course). After writing it, I went back to reading Steven Pinker’s The Better Angels of Our Nature. It was as Pinker was discussing historical changes in our criminal justice system that I made a connection between the two topics which I felt could make for an interesting blog post.

The question that popped into my mind was this: If our brains aren’t always effective at picturing a far-future reward, are they also worse at picturing a far future punishment?

Consider a potential criminal. One of the reasons that we have prison sentences is as a deterrent. However, if potential criminals don’t see a 30 year sentence as 20 percent worse than a 25 year sentence (as we might predict for a rational actor) then the longer sentence is not 20 percent more effective a deterrent.

Furthermore, a crime that would warrant a 30 year sentence could be more rewarding for the potential criminal so it could actually be rational to commit the more rewarding crime and to accept the longer punishment. Crime pays, kids!

I guess some people could draw the conclusion from that that we need even longer sentences to override that bias but that’s not the view I would take. There are many problems associated with increasing the length of a prison sentence such as cost-effectiveness (older people are less likely to commit crimes) and of course, the danger of sentencing an innocent person for even longer.

Pinker references an essay entitled On Crimes and Punishments by the 18th century Italian economist Cesare Beccaria in which Beccaria makes the point that the promptness and certainty of a punishment are more important than its severity.

We now have strong evidence to prove Beccaria right. An effective criminal justice system is one in which criminals expect that both they and their competitors will be punished fairly and predictably by the state because this dissuades them from taking matters into their own hands.

It follows then that instead of politicians consistently trying to portray themselves as “tough on crime” by boasting of their willingness to introduce longer sentences, they should instead realise that a longer sentence is not an equally more effective deterrent.




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