The social perception of risk

Much research on acceptance of risks implies a distinction between objective and subjective definitions of risk. This paper disputes this distinction, arguing instead that discrepancies between public and 'expert' views are to be better understood in terms of differences in how decisions are seen to be made. Risk is a product of decisions taken in response to environmental events, and depends not simply on the threat posed by such events but on the quality of the decisions. A model of decision quality is presented, derived from signal detection theory, which distinguishes between the ability to discriminate between different kinds of events, and the criterion, or level of certainty that is required before a particular response is chosen. Whereas discrimination ability depends on the expertise of decision-makers and the predictability of the events in question, the response criterion reflects considerations of costs, benefits and equity. Where the cost of overlooking a real threat ('false-negative' response) is high, a cautious criterion may be demanded. Where discrimination ability is also seen to be low, the chance of 'false-negatives' may only be adequately reduced at the price of a large number of 'false-positives', or 'unnecessary' protective responses against imagined threats. In extreme cases, this may amount to total opposition to the operation of a system. (author)