uring times of crisis, such as wars, natural disasters or pandemics, citizens look to leaders for guidance. Successful crisis management often depends on mobilizing individual citizens to change their behaviours and make personal sacrifices for the public good 1 . Crucial to this endeavour is trust: citizens are more likely to follow official guidance when they trust their leaders 2 . Here, we investigate public trust in leaders in the context of the COVID-19 pandemic, which continues to threaten millions of lives around the globe at the time of writing 3,4 .Because the novel coronavirus is highly transmissible, a critical factor in limiting pandemic spread is compliance with public health recommendations such as social distancing, physical hygiene and mask wearing 5,6 . Trust in leaders is a strong predictor of citizen compliance with a variety of public health policies [7][8][9][10][11][12] . During pandemics, trust in experts issuing public health guidelines is a key predictor of compliance with those guidelines. For example, during the avian influenza pandemic of 2009 (H1N1), self-reported trust in medical organizations predicted self-reported compliance with protective health measures and vaccination rates 13,14 . During the COVID-19 pandemic, data from several countries show that public trust in scientists, doctors and the government is positively associated with self-reported compliance with public health Moral dilemmas and trust in leaders during a global health crisis

It is known that greater social cohesion increases a group's ability to enforce cooperation. Despite this, defectors often go unpunished, and groups with social structures that are a priori favorable often fail. A critical distinction is required between the structural effect on ability versus willingness to punish. The authors develop a theoretical framework in which variation in a group's social structure generates a tension between ability and willingness to enforce cooperation. Structures that promote ability to punish also often reduce interest in carrying out sanctions, thus changing collective outcomes. The authors' empirical analysis involves a well-defined cooperative dilemma: group lending in Sierra Leone. They complement statistical modeling, based on a data set containing 5,487 group repayments, with ethnographic analysis. They find that (1) structural cohesion only increases economic cooperation between borrowers to a point, beyond which unwillingness outweighs increased ability to punish, reducing group repayments, and that (2) groups with disconnected subgroups perform worse on average. Although borrowers are more willing to punish defectors in the out-subgroup, they are unable to do so effectively.

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It is known that greater social cohesion increases a group’s ability to enforce cooperation. Despite this, defectors often go unpunished and groups with social structures that are a priori favorable often fail. A critical distinction is required between the structural effect on ability versus willingness to punish. We develop a theoretical framework in which variation in a group’s social structure generates a tension between ability and willingness to enforce cooperation. Structures that promote ability to punish also often reduce interest in carrying out sanctions, thus changing collective outcomes. Our empirical analysis involves a well-defined cooperative dilemma: group lending in Sierra Leone. We complement statistical modelling, based on a dataset containing 5,487 group repayments, with ethnographic analysis. We find: (1) Structural cohesion only increases economic cooperation between borrowers to a point, beyond which unwillingness outweighs increased ability to punish, reducing group repayments. (2) Groups with disconnected subgroups perform worse on average. Although borrowers are more willing to punish defectors in the out-subgroup, they are unable to do so effectively.