Drive: The Surprising Truth About What Motivates Us - was published in 2009 and very quickly became a bestseller with its focus on the importance and effectiveness of three intrinsic elements to motivation at work: autonomy, mastery and purpose.
Pink argues that the evidence of scientific studies on motivation and rewards suggests that, for any work task that involves most than the most basic cognitive challenge, basic financial reward systems simply do not work. In fact, they can lead to worse performance.
For simple, straightforward tasks, Pink concedes that traditional financial rewards or a carrot & stick approach to motivation DO work. These can be considered as "external" methods of motivation. They are simple and they still work.