Individual solidarity towards other EU member states during crises is crucial for facilitating a joint EU response without triggering a backlash from the public, which can act as a constraint on further integration (Hooghe & Marks, 2009). Patterns of solidarity differ across crises (Kriesi et al., 2024), yet we do not fully understand why. One set of explanations puts forward that crisis characteristics impact solidarity, with exogenous and symmetric crises being more conducive to solidarity compared to endogenous and asymmetric crises (Ferrara & Kriesi, 2022). Truchlewski et. al. (2025) show that COVID, beyond being perceived as symmetric and exogenous, also generated a high degree of empathy among EU citizens. In turn, this empathy translated into greater support for solidaristic policy. This study aims to untangle the role of crisis characteristics and individual empathy as determinants of EU solidarity.

Psychological research has shown that common difficulties bring individuals together and result in stronger individual bonds (Bastian et al., 2014). This effect has also been experimentally demonstrated for the COVID-19 pandemic, as individuals became more generous towards outsiders when primed with fear about the pandemic (Han et al., 2021). Is this effect specific to COVID or does it travel to other crises that are perceived to be shared among EU member states?

This study employs a parallel encouragement design (Imai et al., 2013) to untangle the role of crisis characteristics and individual empathy. It presents respondents with hypothetical scenarios regarding a future financial crisis. The experiment varies whether the crisis has origins outside the EU or within the EU as well as whether it affects all countries or only some. Second, the experiment presents respondents with a memory task to stimulate empathy with other EU citizens (empathy encouragement), or preferentially with citizens of their own country (empathy discouragement). Finally, all respondents are asked whether they would support an EU aid package aimed at helping affected countries.