Public Reactions to Risk Messages Communicating Different Sources of Uncertainty: An Experimental Test

ABSTRACT

There is an abundant literature on the challenge of integrating uncertainties in experts’ risk assessments, but the evidence on the way they are understood by the public is scarce and mixed. This study aims to better understand the effect of communicating different sources of uncertainty in risk communication. A causal design was employed to test the effect of communicating risk messages varying in type of advisory warning (no risk and suggests no protective measure, or risk and recommends a protective measure) and sources of uncertainty (no uncertainty, divergence between experts, contradictory data, or lack of data) on public reactions. Participants from the general public (N = 434) were randomly assigned to read and react to variants of a fictitious government message discussing the presence of a new micro-organism found in tap water. Multiple analysis of variance showed that to report uncertainty from divergence between experts or from contradictory data reduced the adherence to the message, but not to mention the lack of data. Moreover, the communication of diverse sources of uncertainty did not affect trust in the government when the advisory warning stated there was a risk and recommended a protective measure. These findings have important implications for risk communication.

Key Words:

• uncertainty
• risk perception
• risk communication
• trust

ACKNOWLEDGMENTS

This study was approved by the Research Ethics Board of the University of Ottawa. It was supported financially by the Social Sciences and Humanities Research Council (SSHRC) of Canada and by the McLaughlin Research Chair on Psychosocial Risk of Dr. Louise Lemyre. The authors acknowledge the constructive feedback given by Dr. Patrick Gaudreau and Dr. Pierre Mercier on the methods and analytical strategy.