Message format and audience values: Interactive effects of uncertainty information and environmental attitudes on perceived risk

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