From bonuses, office foosball tables and flextime, to inspirational speeches from managers and decorative prints of soaring eagles, business owners have a broad palette of choices when it comes to motivating their employees (and, ultimately, raising more revenue).

But going down any of these roads involves costs and complex trade offs. Will that rewards program really pay for itself long-term or just induce your sales team to jam in more deals right before the end of the quarter? Is the office ping pong master really making up for his practice time with quicker, clearer thinking? Is my team just secretly sniggering at my inspirational eagle? (The answer to that last one is probably yes.)

Misstep in your efforts at motivation, entrepreneurs worry and you could easily dent the bottom line instead of improving it. So what if I told you a professor out of Wharton has found a totally free, relatively easy-to-implement method to motivate employees and substantially boost revenue?

Tell me how, you'd probably say. Fast Company's Anya Kamenetz explains the basics:

If you want to impact sales and revenue…  you also should consider bringing employees into contact with those who benefit from their work.

That's the finding of Adam Grant, a Wharton professor who studied the training given to 71 new call center employees of a Midwestern software firm. One group of trainees was chosen to meet an "internal customer"--an employee of another department whose salary depends on the sales that the new hires make--during their initial training. In combination with some inspirational words from the CEO, this contact with a real live beneficiary significantly improved both sales and revenue during the employees' first seven weeks.

The difference? A not-insignificant 20% improvement in revenue per shift. Leadership messages from the CEO about purpose, vision, mission, and meaning, however, had no such effect on their own.

Surprised by the magnitude of the impact of such a simple intervention? So was Grant, who explains in the TEDx talk below, how he had to repeat similar experiments at a fundraising call center a half dozen times before he was convinced that such a little thing could make such a big difference. (The talk discusses his call center research but after minute ten is largely directed at educators, so non-teachers may want to sign off early.)

As an entrepreneur you may not have cash to feed your team free lunches or offer a new bonus scheme, but just about every business owner has access to customers and internal beneficiaries of other employees' work on hand. By simply arranging to bring together workers and these folks they help, you may motivate your team more than all the foosball tables and fancy recognition programs in the land.  

How do you provide your team with opportunities to see the impact of their work?