"All truly great thoughts are conceived by walking." Or so said the half-crazed philosopher, Friedrich Nietzsche. Brian Wansink took that one step further and conceived a great advertising thought while getting others to go walking.

Wansink, professor of psychology at Cornell University, recruited 56 subjects to walk a mile route. Half were told to test an MP3 player as they walked, stopping off at six places along the route to monitor sound quality. The other half were told the walk was exercise, and asked to monitor energy levels at the same set places. After the walk they returned their results, collected payment and were told they were free to go. Before they left they were invited to an all-you-can eat buffet the university had laid on.

Unbeknown to them this was the real experiment. After the diners finally departed Wansink rooted through the bins and weighed the left-overs. The results were clear. The group told they were exercising ate far more unhealthy food than those who thought it was a scenic stroll. Despite covering the same distance, at the same speed, the “exercisers" ate 35% more chocolate pudding than the control group.

Wansink attributed the findings to the idea of moral licensing: the tendency to over-compensate and treat ourselves after acting virtuously.

The proof for moral licensing is widespread

If this experiment was a one-off marketers could ignore it. But the evidence for moral licensing is widespread. One of my favourite experiments was conducted in 2011 by Wen-Bin Chiou, of Kaohsiung Medical University in Taiwan. Chiou recruited two groups of daily smokers who both received a course of placebo pills.

The first group knew what they were being given while the second group thought they were having multi-vitamin pills. After the course of pills was completed the groups returned and filled in an hour long survey about their behaviours. Those who thought they had taken multi-vitamins were less likely to have eaten healthily and exercised and more likely to have been binge drinking.

Of course, claimed data can be misleading. So Chiou surreptitiously monitored how many people lit up while filling in the survey. He found that those who had been on the supposed vitamin course were 50% more likely to smoke.

His explanation for this, was that those who had taken multi-vitamin pills thought they had done their bit in being healthy and were therefore more comfortable about indulging their desire for immediate gratification.

The marketing application

The widespread nature of these findings means that we should be applying them to marketing. Products which appeal to a consumer's indulgent side should target consumers in contexts where they're feeling virtuous. Potential options include reaching consumers in gyms, running ads around healthy eating or fitness content, or time targeting Friday afternoon's after a hard week's work.

This applies to a wide variety of products. Not just obvious ones like beer or chocolate, but any brands that consumers see as a treat. This covers a huge range, from lattes or luxury goods to the latest fashion. There are also opportunities in the other direction. Products which seek to appeal to a consumer's moral side might seek to reach consumers as they have succumbed to temptation.