Introduction

Contemporary moral psychology emphasises the universality of moral judgement across age, gender, religion and ethnicity. People's judgement about classic dilemmas is considered to be sensitive to the same moral principles.1 Euthanasia is a moral dilemma, standing at the intersection of medicine and ethics, which has been used by moral psychologists and philosophers as a theme or stimulus to study moral judgement.2–8 Cushman and Young⁹ write, for example, that, ‘ordinary people's judgments are guided by explicit rules like that put forth by the American Medical Association distinguishing between “active” and “passive” euthanasia, the action/omission distinction may play a basic role in moral judgment’ (p1055). Despite philosophical arguments that deny the distinction between active and passive euthanasia,10 surveys show that the public perceive a distinction between these two whereby it may be permissible to withhold treatment and allow a patient to die (ie, passive euthanasia), but it is not permissible to take direct action to kill a patient (ie, active euthanasia).11 However, several studies in Iranian samples showed that, although ‘ordinary people’ clearly distinguish between action and omission, they do not see much of a difference between the two types of euthanasia.8 This difference may show that moral views are, at least to some extent, culture-dependent.

Attitudinal research on euthanasia, as well as moral psychology studies, has been performed extensively in the USA and Europe. With a few notable exceptions, there has been little work that directly compares euthanasia attitudes across cultures. One small qualitative study found dramatic differences among ethnic groups in the USA for starting and stopping life support, noting that the influence of culture, above religious foundations, explains key differences.12 Of particular note here, the Iranian subgroup in that study was the most supportive of starting life support and among the most disapproving of stopping it, followed by the Filipino and the Korean subgroups. There were almost no differences in the responses of Muslim and Christian Iranians, suggesting that the trend was based in culture, not a particular religion.12

Theories of moral judgement consider certain neuropsychological systems, such as affective intuition, to be central to moral judgement.13 Empirical studies have shown that individual differences in dispositional traits are predictive of ethical judgement, reasoning and activities.14 ,15 One key concept in morality is altruism, which is covered by almost every treatise on the evolution of morality.16 ,17 Findings in evolutionary psychology point to the origins of human morality in a set of emotions that make individuals care about the welfare of others (eg, kin altruism), and about cooperation, cheating and norm-following (eg, reciprocal altruism).13 The case of euthanasia provides an opportunity to explore how altruism functions in morality.

The HEXACO model partitions personality factors into six dimensions: Honesty–Humility, Emotionality, Extraversion, Agreeableness, Conscientiousness and Openness. Within the HEXACO model, reciprocal altruism has been represented by the Honesty–Humility and Agreeableness factors. Honesty–Humility and Agreeableness embody individual differences in two aspects of reciprocal altruism, which correspond to the tendency to cooperate with another even when (a) one could get away with defecting and (b) reciprocation has not been forthcoming. Emotionality is related to kin altruism, which involves survival of kin (especially offspring) or personal survival.18 A new facet-level scale has also been incorporated into the HEXACO model, which measures the overall altruism versus antagonism, and contains items describing sympathy, soft-heartedness and generosity. The overall tendency to be altruistic represents a blend of the Honesty–Humility, Agreeableness and Emotionality domains and shows moderate and similar correlations with these three factors, but weak correlations with the remaining HEXACO domains.18 On the basis of this distinction, I propose that Honesty–Humility, Agreeableness and altruism—defined here as a tendency involving willingness to benefit others and unwillingness to harm them—are related to viewing euthanasia as unacceptable. Emotionality is related to harm-avoidant and help-seeking behaviours that are associated with investment in kin and self.18 Because the case of euthanasia, as presented here, does not include a dimension related to administering euthanasia for one's self or kin, I expect Emotionality not to be related to euthanasia.

Thus, this study investigates the association between acceptance of euthanasia and the HEXACO model of personality, with a specific focus on altruism. I expect to find no difference between active and passive euthanasia, showing again that a deed may be considered permission (ie, letting die in passive euthanasia) and still viewed as unacceptable as an action (ie, killing in active euthanasia). Also, by adding a measure of religiosity—which is an especially salient variable for the end-of-life preferences—I will be able to flesh out the extent to which altruism is a unique predictor of attitudes toward euthanasia, if at all.