We do what we imagine others do, even though we know what others do is wrong

Sometimes our understanding of people is so flawed that our attempts to change what they do have the opposite effect.

In Arizona, there is a fascinating national park. In this park, there are trees which have fossilised. Over time, minerals have displaced the organic material in the wood: the forest has literally turned into stone. It is so strange that visitors take mementoes. Irritated that sightseers are carting off fourteen tons of petrified wood a year, staff put up signs to try and discourage the theft. But researchers suspected that the signs, telling visitors that such a huge amount was stolen, ‘mostly a small piece at a time’, were unhelpful.

They had a theory that, just as we mimic people automatically, in bigger things we are also swayed by what we think other people do. This theory predicts that signs telling visitors that other people are stealing from the park will increase the amount of theft. This isn’t how we imagine we work, so well-meaning types create suicide prevention campaigns, eating disorder programs and high-school binge-drinking education efforts which tell their target audience just how big the problem is. Such campaigns have the opposite effect to that intended, and this theory might explain why.

To test their theory, they placed pieces of petrified wood along popular pathways in the park, and rotated different signs on those paths. One of the signs asked ramblers ‘Please don’t remove the petrified wood from the park’. Another told visitors that ‘Many past visitors have removed the petrified wood from the park, changing the natural state of the Petrified Forest’, and was accompanied by a picture of three visitors taking souvenirs.

When no signs were placed along the paths, about 3% of the pieces were stolen. When walkers were asked not to take wood, without any mention of others doing so, this went down marginally to just under 2%. But when the signs told visitors of the damage being done by others (as in the park’s original posters) the theft rate went up dramatically: 8% of the wood was stolen.

Chris Paley's Unthink has been published in six languages. It tells you how you really think rather than how you think you think, and will 'make you happier than a rabbit on a carrot farm'. Buy it here if you want to be that happy.