Economist Steven E. Landsburg has written
Most of economics can be summarized in four words: People respond to incentives. The rest is commentary.But it has been argued that this is not entirely true for some areas of social activity where "intrinsic" motivation is important, such as blood donation. A number of contributions in both the psychology and economics literatures have argued that when people are "intrinsically" motivated to perform a task, as in activities such as blood donation, adding an extrinsic incentive could reduce supply of the activity because the extrinsic incentive might undermine the intrinsic motivation and also attract the "wrong" types of agents to perform the activity. Surveys and laboratory experiments lend support to this non-standard response to economic incentives for the provision of pro-social behaviour. But new research shows that blood donors responding to incentives in the "standard" way; offering donors economic incentives significantly increases turnout and blood units collected, and more so the greater the incentive’s monetary value.
The abstract of the paper, Will There Be Blood? Incentives and Substitution Effects in Pro-social Behavior by Nicola Lacetera, Mario Macis and Robert Slonim, Discussion Paper No. 4567, November 2009, Institute for the Study of Labor, reads,
We examine how economic incentives affect pro-social behavior through the analysis of a unique dataset with information on more than 14,000 American Red Cross blood drives. Our findings are consistent with blood donors responding to incentives in a “standard” way; offering donors economic incentives significantly increases turnout and blood units collected, and more so the greater the incentive’s monetary value. In addition, there is no disproportionate increase in donors who come to a drive but are ineligible to donate when incentives are offered. Further evidence from a small-scale field experiment corroborates these findings and confirms that donors are motivated by the economic value of the items offered. We also find that a substantial fraction of the increase in donations due to incentives may be explained by donors substituting away from neighboring drives toward drives where rewards are offered, and the likelihood of this substitution is higher the higher the monetary value of the incentive offered and if neighboring drives do not offer incentives. Thus, extrinsic incentives motivate pro-social behavior, but unless substitution effects are also considered, the effect of incentives may be overestimated.