Why might recipients react differently and more positively to disaster relief assistance than they do to other forms of aid? In part it is surely related to the simple gratitude felt by people who have just lost much of what they had in a flood or earthquake. But it is also more plausible that such aid is given without a broader political motive. Although U.S. food aid flows according to the size of the surplus domestic crop as much as recipient need, using humanitarian relief to reward or punish countries for U.N. voting records or other diplomatic policies presents a practical challenge -- you can't schedule a disaster. Recipients appear to understand that, and are more likely to view such aid as given in good faith. In the Pakistan case, for example, Andrabi and Das note that the positive impact on attitudes was related to a significant on-the-ground presence of foreigners who were assumed to have purely humanitarian motivations -- aid distribution was not perceived to be (and wasn't) linked to war-fighting efforts.
Aid is likely to be a more effective foreign policy tool when it comes to persuading governments to do things that lack popular support. Creating that popular support in the first place is much harder. Perhaps Turkey's Davutoglu is right to say that even government relations won't improve in the case of Israeli disaster aid -- after all, U.S. humanitarian support in the aftermath of Iran's Bam earthquake only temporarily thawed diplomatic tensions. On the other hand, maybe the assistance can play a small role in improving popular opinion towards Israel in Turkey. For good or ill, that's one more reason for governments to respond with open hearts and open checkbooks whenever disaster strikes worldwide.