How do people use 'killing', 'letting die' and related bioethical concepts? Contrasting descriptive and normative hypotheses.

Bioethicists involved in end-of-life debates routinely distinguish between 'killing' and 'letting die'. Meanwhile, previous work in cognitive science has revealed that when people characterize behaviour as either actively 'doing' or passively 'allowing', they do so not purely on descriptive grounds, but also as a function of the behaviour's perceived morality. In the present report, we extend this line of research by examining how medical students and professionals (N = 184) and laypeople (N = 122) describe physicians' behaviour in end-of-life scenarios. We show that the distinction between 'ending' a patient's life and 'allowing' it to end arises from morally motivated causal selection. That is, when a patient wishes to die, her illness is treated as the cause of death and the doctor is seen as merely allowing her life to end. In contrast, when a patient does not wish to die, the doctor's behaviour is treated as the cause of death and, consequently, the doctor is described as ending the patient's life. This effect emerged regardless of whether the doctor's behaviour was omissive (as in withholding treatment) or commissive (as in applying a lethal injection). In other words, patient consent shapes causal selection in end-of-life situations, and in turn determines whether physicians are seen as 'killing' patients, or merely as 'enabling' their death.