Motivating people is an extremely difficult and delicate task as anyone who’s ever taught, managed, collaborated with or given birth to someone knows. In business, as opposed to say, child-rearing, the debate is slightly less daunting, though not always much clearer. For instance, offering incentives to employees for improved performance is a fairly common approach to encouraging higher sales —though surprisingly unproven by data.

For the most part, the effectiveness of incentives is supported by intuition and some anecdotal evidence. Wouldn’t everyone work at least a little harder for a $100 bill on top of their usual paycheck? Certainly it can’t hurt. But one important open question is whether monetary or tangible (spa retreat, ipod, dinner for two, etc) rewards more efficacious motivators?

Those who advocate for monetary incentives claim they have the greatest appeal given that the winners can do anything with them; what if someone needs an ipod like they need another hole in their head? On the other side, those in favor of tangible incentives argued that money lacks the emotional appeal of, say, a weekend for two at a romantic country inn or swank hotel. But either way, there was nothing to back up either camp.

Thankfully, there is some data on this debate.  A few years ago Goodyear Tire & Rubber Company decided to test which method was more successful in an effort to improve sales of a new line of Aquatred tires. Their plan was simple and elegant: first they ranked their 60 retail districts according to previous sales, then divided them into two groups of equal performance and assigned one group to receive monetary incentives and the other to receive tangible incentives of equal value to the first group.

The results were very interesting; it turned out that the tangible-reward group increased sales by 46% more than the monetary-reward group. They also improved in terms of the mix of products sold by 37%. One explanation, and it seems to me a fairly good one, is that we can visualize tangible rewards (imagine yourself on a Hawaiian beach), which creates an emotional response. Money, on the other hand, is not accompanied by images as often (aside from maybe Scrooge McDuck swimming in piles of it), and lacks the emotional pull that tangible rewards have, so they’re less effective in motivating employees. I guess it’s called “cold, hard cash” rather than “future beach vacation cash” for a reason.