Ebola virus disease (EVD) is a severe infection with an extremely high fatality rate spread through direct contact with body fluids. A promising Ebola vaccine (rVSV-ZEBOV) may soon become universally available. We constructed a game-theoretic model of Ebola incorporating individual decisions to vaccinate. We found that if a population adopts selfishly optimal vaccination strategies, then the population vaccination coverage falls negligibly short of the herd immunity level. We concluded that eradication of Ebola is feasible if voluntary vaccination programmes are coupled with focused public education efforts. We conducted uncertainty and sensitivity analysis to demonstrate that our findings do not depend on the choice of the epidemiological model parameters.

Self-deception, paranoia, and overconfidence involve misbeliefs about the self, others, and world. They are often considered mistaken. Here we explore whether they might be adaptive, and further, whether they might be explicable in Bayesian terms. We administered a difficult perceptual judgment task with and without social influence (suggestions from a cooperating or competing partner). Crucially, the social influence was uninformative. We found that participants heeded the suggestions most under the most uncertain conditions and that they did so with high confidence, particularly if they were more paranoid. Model fitting to participant behavior revealed that their prior beliefs changed depending on whether the partner was a collaborator or competitor, however, those beliefs did not differ as a function of paranoia. Instead, paranoia, self-deception, and overconfidence were associated with participants’ perceived instability of their own performance. These data are consistent with the idea that self-deception, paranoia, and overconfidence flourish under uncertainty, and have their roots in low self-esteem, rather than excessive social concern. The model suggests that spurious beliefs can have value–self-deception is irrational yet can facilitate optimal behavior. This occurs even at the expense of monetary rewards, perhaps explaining why self-deception and paranoia contribute to costly decisions which can spark financial crashes and devastating wars.

Humans lie to one another frequently with local and global consequences. Here we examine and operationalize the choice to lie using a mathematical model which we fit to participant behavior. This model combines perceptions of exploitability and fairness attitudes to explore the interaction between two types of utility: instrumental utility and moral utility. These utilities differed in concert with individual differences in participants’ behavioral traits, and those differences underwrote lies with distinct motivations. Strategic deception – wherein the lie benefits the individual - was common amongst people with elevated subclinical psychopathic traits in the absence of paranoia. It was driven by differences in instrumental utility. Whereas pathological deception – which has no apparent economic or strategic benefit – was common among highly paranoid participants (who also had elevated scores on dark triad personality traits) and was governed by the moral utility of the lie. They lied for little apparent benefit because they failed to modulate their fairness attitudes in line with the decision context. These data challenge accounts of deception that suggest deceiving oneself is a prerequisite to successful lying. They also oppose accounts of psychopathology that connect psychopathic traits to pathological lying, and theories that implicate strategic social decision-making dysfunction in paranoia. More broadly, these data highlight the importance of individual differences in efforts to mitigate deception, which have thus far, largely focused on incentive structures and decision architectures.

Humans lie to one another frequently with local and global consequences. Here we examine and operationalize the choice to lie using a mathematical model which we fit to participant behavior. This model combines perceptions of exploitability and fairness attitudes to explore the interaction between two types of utility: instrumental utility and moral utility. These utilities differed in concert with individual differences in participants’ behavioral traits, and those differences underwrote lies with distinct motivations. Strategic deception – wherein the lie benefits the individual - was common amongst people with elevated subclinical psychopathic traits in the absence of paranoia. It was driven by differences in instrumental utility. Whereas pathological deception – which has no apparent economic or strategic benefit – was common among highly paranoid participants (who also had elevated scores on dark triad personality traits) and was governed by the moral utility of the lie. They lied for little apparent benefit because they failed to modulate their fairness attitudes in line with the decision context. These data challenge accounts of deception that suggest deceiving oneself is a prerequisite to successful lying. They also oppose accounts of psychopathology that connect psychopathic traits to pathological lying, and theories that implicate strategic social decision-making dysfunction in paranoia. More broadly, these data highlight the importance of individual differences in efforts to mitigate deception, which have thus far, largely focused on incentive structures and decision architectures.

Self-deception, paranoia, and overconfidence involve misbeliefs about self, others, and world. They are often considered mistaken. Here we explore whether they might be adaptive, and further, whether they might be explicable in normative Bayesian terms. We administered a difficult perceptual judgment task with and without social influence (suggestions from a cooperating or competing partner). Crucially, the social influence was uninformative. We found that participants heeded the suggestions most under the most uncertain conditions and that they did so with high confidence, particularly if they were more paranoid. Model fitting to participant behavior revealed that their prior beliefs changed depending on whether the partner was a collaborator or competitor, however, those beliefs did not differ as a function of paranoia. Instead, paranoia, self-deception, and overconfidence were associated with participants’ perceived instability of their own performance. These data are consistent with the idea that self-deception, paranoia, and overconfidence flourish under uncertainty, and have their roots in low self-esteem, rather than excessive social concern. The normative model suggests that spurious beliefs can have value – self-deception is irrational yet can facilitate optimal behavior. This occurs even at the expense of monetary rewards, perhaps explaining why self-deception and paranoia contribute to costly decisions which can spark financial crashes and costly wars.