Ninjas in Supply Chain (like yours truly), front-line customer service, Accounting, anywhere and everywhere are motivated by a number of factors. It’s not necessarily fruit, either. (From the popular mobile and Microsoft Kinect game Fruit Ninja.) For some, motivation comes from factors such as a good work environment (next to a beach?), money, or other external factors called extrinsic motivators. For most, motivation comes from sources of intrinsic motivators such as vertical job ascension (read: promotions), recognition of work, and other internal, personal factors.
I recently stumbled upon a TED talk of Dan Pink back in July 2009: The puzzle of motivation. What a great talk. You can watch the video here. 
Dan discusses the people aspect of motivation and their true motivators — the battle of intrinsic and extrinsic motivators. In business school, half the students would argue money is a massive motivator. However, money is also one of those factors which only causes workers to not only want more but people then tend to EXPECT compensation (salary bumps, bonuses, etc.) as normal procedure. Dan adds that compensation actually motivates those with finite, discrete processes, but compensation does NOT motivate those with more challenging, innovative tasks. In fact, “these contingent motivators — if you do this, then you get that — work in some circumstances but for a lot of tasks, they actually either don’t work or often, do harm.” 
Dan cites several social experiments including the Candle Problem from 1945 by an American Psychologist named Karl Duncker . Groups were tasked to attach a candle to a wall so that the wax does not drop onto the table. An illustration of the materials is shown in the figure below .
Sam Glucksberg, a Psychology Professor at Princeton University, pivoted on the Candle Problem by gathering participants and challenged them to solve the problem based on: 1) solve to help establish norms vs. 2) incentivize monetary incentives (top 25% of fastest times earn $5; fastest time earns $20). The incentivized group solved the problem faster than the group who were tasked to help establish norms. NOT! The incentivized group actually solved the problem 3.5 minutes SLOWER than the group without the incentives! (I tricked you, didn’t I?)
Another iteration was performed on the Candle Problem… I won’t describe it now, but I’ll let you watch Dan’s video for more information. What Glucksberg found was that incentives only motivate people when the path to solve are explicit and known — a concept Dan Pink touches on called Functional Fixedness. Incentives actually do NOT foster innovation and creativity! Who would have thought?! This tells us that today’s motivation and incentives programs are actually hampering people from using their creativity to solve problems!
This TED talk was one of the best I’ve heard (and there are many on TED). There has been so much attention recently regarding intrinsic vs. extrinsic motivators. This TED Talk further supports intrinsic motivation as THE way to foster creativity and innovation and to ultimately higher performing and happier employees. The incentives today of if-then only dulls creativity, and will continually hamper people from thinking creatively to solve today’s problems. So as leaders in our respective domains, remember to motivate fellow Ninjas with intrinsic motivators and as Dan Pink says, “we can strengthen our businesses, we can solve a lot of those candle problems, and maybe, maybe, maybe, we can change the world.” 
 Wikipedia contributors. “Candle problem.” Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 7 Sep. 2012. Web. 19 Sep. 2012.
 Dewey, Russ (2007). From Puzzles. Intro Psych. [Website]. Retrieved September 19, 2012, from http://www.intropsych.com/ch07_cognition/puzzles.html