Reluctance to Vaccinate: Omission Bias and Ambiguity

Abstract

Subjects are reluctant to vaccinate a (hypothetical) child when the vaccination itself can cause death, even when this is much less likely than death from the disease prevented. This effect is even greater when there is a 'risk group' for death (with its overall probability held constant), even though the test for membership in the risk group is unavailable. This effect cannot be explained in terms of a tendency to assume that the child is in the risk group. A risk group for death from the disease has no effect on reluctance to vaccinate. The reluctance is an example of omission bias (Spranca, Minsk &Baron, in press), an overgeneralization of a distinction between commissions and omissions to a case in which it is irrelevant. Likewise, it would ordinarily be prudent to find out whether a child is in a risk group before acting, but in this case it is impossible, so knowledge of the existence of the risk group is irrelevant. The risk-group effect is consistent with Frisch & Baron's (1988) interpretation of ambiguity. KEY WORDS Omission bias Ambiguity VaccinationThe present study concerns the role of two biases in hypothetical decisions about vaccinations. One bias is the tendency to favor omissions over commissions, especially when either one might cause harm. We show that some people think that it is worse to vaccinate a child when the vaccination can cause harm than not to vaccinate, even though vaccination reduces the risk of harm overall. The other bias is the tendency to withhold action when missing information about probabilities is salientsuch as whether the child is in a risk group susceptible to harm from the vaccineeven though the missing information cannot be obtained. We show that this bias is found even when the overall probability of each outcome is clearly constant across the conditions compared. We take both of these effects to be overgeneralizations of principles or heuristics that are generally useful to situations in which they are not useful.Consider first what we shall call omission bias, the tendency to favor omissions (such as letting someone die) over otherwise equivalent commissions (such as killing someone actively). In most cases, we have good reasons for the distinction between omissions and commissions: omissions may result from ignorance, and commissions usually do not; commissions usually involve more malicious intentions than the corresponding omissions; and commissions usually involve more effort, itself a sign of stronger intentions. In addition, when people know that harmful omissions are socially acceptable, they look out for themselves; this self-help principle is, arguably, sometimes the most efficient way to prevent harm.

Regret as autobiographical memory

“…Also, since it has been shown that actions are more likely to be associated with immoral acts (Ritov & Baron, 1990;Spranca, Minsk, & Baron, 1991), being asked to think about the consequences of one"s regrettable behaviours, which are likely to include feelings of guilt, shame or remorse, might actually inhibit the search for consequences of action regrets relative to inactions.…”

“…In health and medical contexts the prospect of regret has been shown to bias people"s judgement in decisions concerning both real (Asch et al, 1994;Meszaros et al, 1996;Ziarnowsky, Brewer & Weber, 2008) and hypothetical vaccinations Connolly & Reb, 2005;Ritov & Baron, 1990). The increasing involvement of patients in medical decision making is seen as a major source of potential regret (Brehaut et al, 2003) and the anticipation of regret is recognised as something likely to shape treatment choices.…”

Paradise to parking lots: Creation versus maintenance of a public good

“…The omission bias reflects a preference for inaction that results in a worse outcome rather than action that results in the same worse outcome. For example, subjects have revealed a preference for withholding vaccination for a child because the vaccination may itself cause the child's death, even if the risk of death from the prevented disease is even greater (Ritov and Baron, 1990). Andreoni's (1995) warm glow/cold prickle theory is a mirror image of the omission bias, a commission bias; a preference for action that results in a beneficial outcome rather than inaction that results in the same beneficial outcome.…”

The Origins and Extent of Entrepreneurial Action-Orientedness: An Experimental Study

“…On the contrary, it might also be that action-orientedness is related to opportunity recognition or the tendency to exploit opportunities. For this reason, biases towards inaction are mostly studied in hypothetical settings (Ritov and Baron, 1990;Patt and Zeckhauser, 2000;Tanner and Medin, 2004). This does not often lead to findings that are relevant from an economic perspective because incentives are lacking.…”