Omission bias in vaccination decisions: Where’s the “omission”? Where’s the “bias”?

Several studies have reported that parents are often reluctant to vaccinate their own or other people’s children, even when the balance of health risks and benefits clearly favors vaccination. This reluctance has been interpreted as a manifestation of “omission bias”, a general tendency to prefer inactive to active options even when inaction leads to worse outcomes or greater risks. The research raises significant public health concerns as well as worries about human decision biases in general. In this paper we argue that existing research on vaccination decisions has not convincingly demonstrated any general reluctance to vaccinate nor has it made the case that such a tendency, if found, would constitute a bias. We identify several conceptual and methodological issues that, we argue, cloud interpretation of earlier studies. In a new questionnaire-based study (Experiment 1) we examined the vaccination decisions of undergraduate students (N=103) and non-student adults (N=192). In both groups a clear majority chose to vaccinate when disease and vaccination risks were balanced. Experiments 2 and 3 identify several problems associated with the measures used in earlier studies, and show how these problems could have led to the misleading appearance of majority anti-vaccination preferences. In our data, vaccination intentions appear to be less a function of generalized preferences for action or inaction than they are of the regret respondents expect to feel if vaccination or non-vaccination were to lead to a poor outcome. Regret-avoiding choices led some respondents to favor vaccination, others to oppose it. In two follow-up studies, few respondents mentioned action or inaction per se in explaining their choices. We conclude that there is no convincing evidence that a generalized “omission bias” plays any important role in vaccination decisions.     

Friend networking sites and their relationship to adolescents' well-being and social self-esteem.

The aim of this study was to investigate the consequences of friend networking sites (e.g., Friendster, MySpace) for adolescents' self-esteem and well-being. We conducted a survey among 881 adolescents (10-19-year-olds) who had an online profile on a Dutch friend networking site. Using structural equation modeling, we found that the frequency with which adolescents used the site had an indirect effect on their social self-esteem and well-being. The use of the friend networking site stimulated the number of relationships formed on the site, the frequency with which adolescents received feedback on their profiles, and the tone (i.e., positive vs. negative) of this feedback. Positive feedback on the profiles enhanced adolescents' social self-esteem and well-being, whereas negative feedback decreased their self-esteem and well-being.     

The structure of affective action representations: temporal binding of affective response codes

Two experiments examined the hypothesis that preparing an action with a specific affective connotation involves the binding of this action to an affective code reflecting this connotation. This integration into an action plan should lead to a temporary occupation of the affective code, which should impair the concurrent representation of affectively congruent events, such as the planning of another action with the same valence. This hypothesis was tested with a dual-task setup that required a speeded choice between approach- and avoidance-type lever movements after having planned and before having executed an evaluative button press. In line with the code-occupation hypothesis, slower lever movements were observed when the lever movement was affectively compatible with the prepared evaluative button press than when the two actions were affectively incompatible. Lever movements related to approach and avoidance and evaluative button presses thus seem to share a code that represents affective meaning. A model of affective action control that is based on the theory of event coding is discussed.     

Planning bridges the intention–behaviour gap: Age makes a difference and strategy use explains why

Objective: This study examines age-differential association patterns between intentions, planning and physical activity in young and middle-aged individuals. The effectiveness of planning to bridge the intention–behaviour gap is assumed to increase with advancing age. We explore the use of behaviour change strategies that include selection, optimisation and compensation (SOC) as underlying mechanisms for age differences. Methods: In N = 265 employees of a national railway company (aged 19–64 years), intentions, planning, SOC strategy use and physical activity were assessed at baseline (Time 1) and again 1 month later (Time 2). Hypotheses were tested in two different path models. Results: Age moderates the extent to which planning mediates the intention–behaviour relation due to an increasing strength of the planning–behaviour link. As a possible psychological mechanism for these age differences, we identified SOC strategy use as a mediator of the age by planning interaction effect on physical activity. Conclusion: These findings suggest differential mechanisms in behaviour regulation in young and middle-aged individuals.