Abstract:

The communication of risk assessment uncertainty to the public and to policy makers is a matter of increasing concern and debate. Although both past research and psychological theory predict that presenting information about the uncertainty associated with a risk estimate will increase perceived risk, recent work (Johnson & Slovic, 1995) suggests that it may in fact have a negligible impact on the average response to hazard risks. The present study argues that, when hazards are evaluated in the context of risk-benefits tradeoffs, uncertainty information interacts with individual value differences in its effects on perceived risk. One hundred and seventy-seven subjects evaluated five hypothetical environmental risk scenarios, with probabilistic risk information presented in one of four ways: (1) a single best estimate, (2) a best estimate with a verbal qualification of its associated uncertainty, (3) a numerical range centered on that estimate, and (4) a numerical range with the values explained as the conclusions of two different sources with opposing biases. Average level of perceived risk did not differ across these experimental groups, but type of uncertainty information and the individual's level of environmental concern had an interactive effect. (C) 2000 Academic Press.