Why do international non-governmental organizations (INGOs) expend considerable material and communicative resources to help alleviate some forms of humanitarian crises, while other crises fail to attract similar levels of attention? How can we explain why some humanitarian issues are selected for attention by transnational advocacy networks (TANs) over others? Existing scholarship has posited that issue attributes help determine the advocacy agendas of transnational actors. Issues which fit well with pre-existing national and international agendas, resonate with accepted transnational norms, or exude a simple causal chain of blame, such as those pertaining to bodily harm and legal ill-treatment of innocent or vulnerable people, are putatively conducive to selection. However, these explanations remain without empirical corroboration, with recent empirical studies suggesting that variation in the issues which are prioritized by transnational actors cannot be accounted for through existing explanatory frameworks. This study will advance a political psychology approach to the question of humanitarian issue selection by TANs. Drawing on insights from behavioural decision research, particularly advances in theoretical and experimental work in cognitive psychology, it empirically tests the proposition that heuristic-led judgement on the part of key decision-makers in TANs is a central determinant in the (non-)adoption of humanitarian issues by advocacy networks. The proposed explanation will be investigated empirically through a mixed-method research design, encompassing a paired-conjoint experiment with UK NGO workers and qualitative case studies involving three major humanitarian organizations.