Working Papers

How Effective are Reminders and Frames in Incentivizing Blood Donations?


This paper studies the effects of reminders, and frames used to invoke higher levels of empathy and altruistic motives on the willingness to donate blood. We have conducted a randomized field experiment with 3236 blood donors from Bosnia and Herzegovina, in order to test how effective frames were when used in letter soliciting blood donations. Further, we tested the effectiveness of the letter itself which served as a specific reminder, making the need for blood more salient. Our baseline group did not receive any letter. Another seven groups received letters which differed in terms of goal framing; whether a specific victim was identified; and the gender of a victim. We found that a reminder of the need for blood in the form of a simple letter increases the probability of coming to donate blood by 62% and donors’ turnout in the next 9 months by 26%, relative to the baseline group, suggesting that reminder letters may serve as a cost-effective policy tool. Notably, we rule out the temporal substitution between future and present donations. At the same time, we found that the framing of the letter had relatively little effect when donors are allowed one month period to make their donation decision.

Work in Progress

Gender-Based Favouritism in Blood Donations: Evidence from a Field Experiment


This paper provides the first evidence of the existence of gender-based favoritism in life saving decisions to donate blood. We conduct a field experiment among blood donors from Bosnia and Herzegovina where we exogenously manipulate the signal of a blood recipient’s gender by adding his/her name, and photograph, to a letter soliciting blood donation. Motivated by the literature on identity, we test the influence on donation behavior of two dimensions of shared identity between donor and recipient – gender and age. 74% more blood donors donate if the potential blood recipient is of the same gender. This result is mostly driven by male donors donating to a male recipient. In contrast to gender identity being an important determinant in fostering donors’ participation rates, being of similar age to the blood recipient has relatively little effect. By identifying an important factor that influences willingness to give blood, our results have implications for better targeting of campaigns to increase blood donations.

Hormones are Thicker than Blood: Field Experiment in Blood Donations (jointly with Dejan Kovač , Irena Jukić, and Vanja Lončar)

Abstract (full paper available on request)

Given the presence of competing predictions on the association of oxytocin with pro-social behaviors (Kosfeld, Heinrichs, Zak, Fischbacher & Fehr, 2005; Zak, Stanton & Ahmadi, 2007; Barraza & Zak, 2009; Nave, Camerer, & McCullough, 2015), we used field experiment in which we employed the natural setting of blood donations to test if oxytocin can serve as proxy for empathy. We aimed to induce different levels of empathy among blood donors who came to the Croatian Institute for Transfusion Medicine by showing them neutral or emotional video. While randomly chosen donors from the control group were watching a neutral video when giving blood, the donors from the first and second treatment group were watching an emotional video.  In addition to watching an emotional video, donors from the second treatment group were given a gift which relates to the emotional story from the video. Hence, we were able to observe the differences in initial and induced oxytocin plasma levels within donors and between groups. Further, we could compare the induced empathy measured by the Interpersonal Reactivity Index questioner (Davis, 1980) with the blood donors’ altruism obtained from playing the dictator game shortly after the blood donation – this enabled us to test Empathy-Altruism hypothesis (Batson, 1987) in case of blood donations.

Preferences, Information, and Entry into Academic Careers (jointly with Patrick Gaule and Ina Ganguli)

(Abstract  available on request)

The Influence of Introducing Commercial Plasma Centers on Giving Blood Voluntarily  (jointly with Nicola Lacetera and Mario Macis)

(Abstract  available on request)

Newspaper Articles

(in Bosnian/Serbian/Croatian language only)

(in Czech language only)