The Sting of Rejection: Deferring Blood Donors due to Low Hemoglobin Values Reduces Future Returns.

BACKGROUND: Roughly one quarter of short-term temporary deferrals (STTD) of blood donors are low-hemoglobin deferrals (LHD), i.e. STTD due to a hemoglobin (Hb) value falling below a cutoff of 125 g/L for female and 135 g/L for male donors. Since voluntarily donating blood is a prosocial activity, donors may perceive deferral as social exclusion, which can cause social pain, decrease self-esteem, and lead to antisocial behavior. However, little is known about the causal impacts of LHD on donor return. STUDY DESIGN AND METHODS: We conducted a quasi-experiment with 80,060 donors invited to blood drives in the canton of Zurich, Switzerland, between 2009 and 2014. Within a narrow window of Hb values around the predetermined cutoff, the rate of LHD jumps discontinuously. This discontinuous jump allows us to quantify the causal effects of LHD on donor return, as it is uncorrelated with other unobserved factors that may also affect donor return. RESULTS: We found different behavioral reactions to LHD for female and male donors. Female donors do not react to the first LHD. However, after any repeated LHD, they are 13.53 percentage points (p <0.001) less likely to make at least 1 donation attempt within the next 18 months and make 0.389 fewer donation attempts (p <0.001). Male donors react to the first LHD. They are 5.32 percentage points (p = 0.139) less likely to make at least 1 donation attempt over the next 18 months and make 0.227 (p = 0.018) fewer donation attempts. After any repeated LHD, male donors are 13.30 percentage points (p = 0.004) less likely to make at least 1 donation attempt and make 0.152 (p = 0.308) fewer donation attempts. CONCLUSION: LHD have detrimental impacts on donor return, especially if they occur repeatedly - suggesting that avoiding false LHD and helping donors to better cope with them helps to maintain the pool of prospective donors.

Spillovers of prosocial motivation: Evidence from an intervention study on blood donors.

Blood donations are increasingly important for medical procedures, while meeting demand is challenging. This paper studies the role of spillovers arising from social interactions in the context of voluntary blood donations. We analyze a large-scale intervention among pairs of blood donors who live at the same street address. A quasi-random phone call provides the instrument for identifying the extent to which the propensity to donate spills over within these pairs. Spillovers transmit 41% to 46% of the behavioral impulse from one donor to the peer. This creates a significant social multiplier, ranging between 1.7 and 1.85. There is no evidence that these spillovers lead to intertemporal substitution. Taken together, our findings indicate that policy interventions have a substantially larger effect when targeted towards pairs instead of isolated individuals.

The risk elicitation puzzle.

Evidence shows that people's preference for risk changes considerably when measured using different methods, which led us to question whether the common practice of using a single behavioural elicitation method (EM) reflects a valid measure. The present study addresses this question by examining the across-methods consistency of observed risk preferences in 1,507 healthy participants using six EMs. Our analyses show that risk preferences are not consistent across methods when operationalized on an absolute scale, a rank scale or the level of model parameters of cumulative prospect theory. This is at least partly explained by the finding that participants do not consistently follow the same decision strategy across EMs. After controlling for methodological and human factors that may impede consistency, our results challenge the view that different EMs manage to stably capture risk preference. Instead, we interpret the results as suggesting that risk preferences may be constructed when they are elicited, and different cognitive processes can lead to varying preferences.

Call of duty: the effects of phone calls on blood donor motivation.

BACKGROUND: Little is known about the long-term effects of interventions aimed at increasing turnout among voluntary blood donors. STUDY DESIGN AND METHODS: We use a retrospective natural experiment with all 40,653 donors who were repeatedly invited to blood drives in Zurich, Switzerland, between 2010 and 2013. The intervention is a quasi-randomized phone call informing donors of a current shortage of their blood type. The panel structure of the data allows identification of different types of donors reacting to the phone call. RESULTS: Our analysis reveals two types. Type 1 donors make up 27.1% of the population. They are highly motivated and exhibit a baseline donation rate of 59.4% (p < 0.001). The phone call raises their probability to donate by 9.9% at the upcoming blood drive (p < 0.001). However, the phone call reduces their donation rate by 2.3% (p = 0.003) at each future blood drive. In contrast, the 72.9% of Type 2 donors exhibit a low baseline donation rate of 5.8% (p < 0.001). The phone call raises their probability to donate by 5.8% at the upcoming blood drive (p < 0.001). Moreover, the phone call leads to habit formation in Type 2 donors and increases their donation rate by 2.1% at the next blood drive (p = 0.03). CONCLUSION: Behavioral interventions are effective at increasing donation rates in the short run. However, they can crowd out the intrinsic motivation of the most motivated donors. Thus, blood donation services should avoid interventions for highly motivated donors and target them at irregular donors. Our results also sound a warning on using other interventions.

Linking brain structure and activation in temporoparietal junction to explain the neurobiology of human altruism.

Human altruism shaped our evolutionary history and pervades social and political life. There are, however, enormous individual differences in altruism. Some people are almost completely selfish, while others display strong altruism, and the factors behind this heterogeneity are only poorly understood. We examine the neuroanatomical basis of these differences with voxel-based morphometry and show that gray matter (GM) volume in the right temporoparietal junction (TPJ) is strongly associated with both individuals' altruism and the individual-specific conditions under which this brain region is recruited during altruistic decision making. Thus, individual differences in GM volume in TPJ not only translate into individual differences in the general propensity to behave altruistically, but they also create a link between brain structure and brain function by indicating the conditions under which individuals are likely to recruit this region when they face a conflict between altruistic and selfish acts.