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Abstract

In public health contexts, adherence to official guidance depends critically on effective information processing, as failure to integrate health information appropriately may result in inadequate behavioural change and can be detrimental for population-level outcomes. Public health information is delivered via evidence and advice. Existing research suggests that people might deviate from optimality when updating beliefs in response to evidence and advice. In particular, exhibiting conservatism —people integrate evidence less than they should — and egocentric discounting —people integrate advice less than expected. While there is abundant research on evidence and advice integration, little is known about whether people are more optimal when integrating evidence or advice into their beliefs, if they can effectively combine evidence and advice, and which factors might deter from the optimal integration of evidence and advice. Using Bayesian standards, this thesis introduces a novel paradigm and an optimality measure that enables direct comparison of advice and evidence integration, and to examine the combination of evidence and advice integration in belief-updating, providing insights into potential cognitive mechanisms limiting optimal integration.

In three experiments (N = 632), we examined how participants integrated advice and evidence when making pharmaceutical investment decisions. The paradigm manipulated information strength, as well as presentation order, format, and sequence to understand if people integrate medical information optimally and which factors impact optimal integration. Findings show that people exhibit suboptimal, conservative integration of evidence and advice, suggesting cognitive capacity constraints rather than fundamental departures from rationality.

Conservatism increased for high quality information and when combining multiple pieces of evidence. Recency effects suggest that conservative belief updating results from cognitive capacity limitations. Participants were also more optimal when they received only advice, not evidence. However, participants also showed a marked preference for evidence over advice; relying on evidence and neglecting advice, which led to decreases in optimality. Sequential advice presentation was more effective than simultaneous presentation; and consensus advice was beneficial when it agreed with existing beliefs. Furthermore, disagreements predicted the greatest conservatism, but agreement/disagreement asymmetries in responsiveness existed only for advice and not evidence. Taken together, this research provides new insights into how belief updating should be studied, providing new methods and highlighting the critical importance of distinguishing responsiveness from optimality. Practically, our findings offer important suggestions for public health, science communication, and policy development.

Publication Type:	Thesis (Doctoral)
Subjects:	B Philosophy. Psychology. Religion > BF Psychology H Social Sciences > HA Statistics R Medicine > RA Public aspects of medicine > RA0421 Public health. Hygiene. Preventive Medicine
Departments:	School of Health & Medical Sciences > Department of Psychology & Neuroscience School of Health & Medical Sciences > School of Health & Medical Sciences Doctoral Theses Doctoral Theses

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