The answer lies in what the authors call the abundance effect: “the presence of abundant wealth leads to more frequent cheating than an environment of scarcity.”
To test this, the authors ran a little experiment. They asked people to make as many words as possible out of a random selection of seven letters, paying $3 to anyone who made 12 or more, allowing subjects to report their own success. People were then split into two groups. One group went to a room in which there was a table containing just a few dollars. The other group were sent to a room containing a large pile - $7000 - of dollar bills.
And in this room, 86.4% of players over-stated their success, compared to just 47.6% in the room with little cash.
The mere presence of money, then, can significantly increase cheating.
This could be because the mere presence of wealth increases people’s desire for it; people figure “with this much wealth around, why shouldn‘t I get a bit of it?” Or it could be that, as experimental studies have shown, merely thinking about money makes people more selfish, less willing to help others (pdf) and more willing to be alone (pdf).
And this is where there’s a huge difference between now and the 1930s. Today, we are surrounded by reminders of wealth: celebrity magazines, adverts and many TV programmes. The abundance effect predicts that this will make us more prone to selfish cheating.
This has an obvious implication - that inequality (pdf) causes crime (pdf). Other peoples’ wealth raises crime via the abundance effect, whilst one’s own poverty reduces the costs of crime.
In this light, the Conservatives’ interest in behavioural economics might not be wholly wise - because behavioural economics can have some messages Tories won’t like at all.