Further, there is a growing body of evidence, which suggests for open, creative activities, the presence of an If/Then reward (If you do this, Then I'll give you a Scooby Snack), also decreases performance. The logic here is that we are so focused on the reward, we become closed to alternative, non-obvious solutions to a problem. So the presence of a reward not only decreases motivation but also performance. The goal of having a reward in the first place was exactly the opposite.
This has important implications for us as individuals - in how we are incentivized, in how we manage our teams, in how we relate to our kids. For instance, if you tell your child you'll give them a toy for reading a book, you erode the enjoyment of reading and transpose it onto the toy. Later on, no toy means no enjoyment in reading. Equally, that manager you offered a 10% cut of additional revenue, will actually start only doing it for the bonus, and will be closed to new ways to deliver the sales.
This also applies in agency life, in how we work with clients. Some clients look to increase performance by setting stretch goals with additional payments if they are achieved. The aim is to incentivize 'extra mile' performance. But the effect could be exactly the opposite. If the team intrinsically enjoys the work, adding a bonus will erode that fun, and also make their thinking more linear. Later on, if budgets decrease and there's no pot for bonuses, the program could under-perform the level it would have done prior, absent the bonus.
You can't give people motivation. You have to nurture it. Dangling a carrot can debase the level of motivation, reducing the activity to a transaction not a calling. According to the research, a better approach to motivating your team or agency, might be to clarify the mission and their role, give them all the resources they need (including financial), then let their intrinsic passion do the rest.