Stability and inoculation of risk comparisons' effects under conflict: replicating and extending the "asbestos jury" study by Slovic et al

Our plain-English summary of Stability and inoculation of risk comparisons' effects under conflict: replicating and extending the "asbestos jury" study by Slovic et al, by B.B. Johnson (Risk Analysis, 2002).

The study

• Author: B.B. Johnson
• Journal: Risk Analysis
• Published: 2002;22(4):777-88
• Cited by: 5 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Promotion or criticism of risk comparisons in risk communication has far exceeded empirical tests of their effects. Slovic et al. (1990) experimented with a hypothetical jury trial in which an asbestos-installing firm was accused of subjecting school occupants to unreasonable risk. A risk comparison sharply reduced subjects' estimates of risk and judgments that the firm was guilty, but a critique of the risk comparison had risk estimates and guilt judgments rebounding to the original (without risk comparison) level. Slovic et al. concluded that risk comparisons' effects were highly unstable, at least in conflict-ridden situations such as a jury trial. The present study replicates and extends this important study, using the same stimuli and questions. The respective effects of the risk comparison and the critique recurred, although much less sharply than in Slovic et al. Moreover, judgments of guilt, risk, and other aspects of the case seemed shaped more by demographics and beliefs about risk generically (e.g., about the likelihood of cancer after exposure to a carcinogen) than by either risk comparison or critique. A variant design, in which the defense's expert witness dismissed potential criticisms of the risk comparison, appeared to "inoculate" people against shifting their views after seeing the critique. Overall, these results show that risk comparisons might change some beliefs about risks in conflict and that "inoculation" can reduce vulnerability to criticism. However, the results also show strong limits on effects of both comparisons and their critiques: they shifted only a minority of judgments and had small effects relative to people's social locations and prior risk beliefs.

In plain English

This experiment studied reactions to risk comparisons, not asbestos disease. The author replicated and extended a 1990 experiment by Slovic and colleagues. Participants played jurors in a hypothetical school board lawsuit against an asbestos installer. Students attending that school for three years had an increased lifetime risk of death of 0.23 per million, based on an average air concentration of 0.001 fibers per cubic centimeter. In all, 238 adults from 23 civic groups, mostly in central New Jersey, read one of five versions, some adding a defense expert's risk comparison, a plaintiff expert's critique, and the defense expert's advance rebuttal of criticisms ("inoculation"). The comparison tended to lower risk ratings and guilty verdicts, the critique to raise them; neither shift was statistically significant. Most people did not change their views. After the critique, no inoculation-group member changed a guilt judgment, versus 6 of 47 in the critique group. Guilty verdicts went with being female, poorer or less educated, and believing any carcinogen exposure leads to cancer. The author concluded that risk comparisons under conflict are unlikely to have much effect.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Experiment (replication and extension of an earlier study) in which adults read one of five versions of a hypothetical asbestos jury trial and answered questionnaires
• Who was studied: 238 adults (opportunity samples) recruited through 23 civic organizations, mostly in central New Jersey; 63% female, aged 19 to 89
• Exposure: No real exposure was studied. Participants read a hypothetical scenario about properly installed asbestos in a junior high school. In it, students attending the school for three years had an increased lifetime risk of death of 0.23 per million, based on an average air concentration of 0.001 fibers per cubic centimeter; no fiber type was named. The experimental conditions were background only, a risk comparison table with defense testimony, a plaintiff expert's critique of the comparison, and an 'inoculation' text in which the defense expert dismissed expected criticisms.
• Main results:
  • Mean judged risk (1 to 7 scale) ranged from 2.38 to 3.20 across the baseline, comparison and critique conditions. It was lowest in the comparison group (2.38, N = 42) versus baseline (3.07, N = 43), a difference that was only marginally significant (t = 1.8, p less than 0.10).
  • In this study, 20% to 37% of participants found the company guilty, depending on condition; none of the shifts in guilt between conditions were statistically significant
  • Within the critique group (N = 45), most did not change their answers after reading the critique. 60% did not change their risk rating (33% increased it), and 87% did not change their guilt judgment (11% changed toward guilty).
  • Six of 47 people (13%) in the critique group changed their guilt judgment after the critique, compared with none of 50 in the group that first read the inoculation text. In the inoculation group, mean risk ratings declined slightly after the critique (4.96 to 4.86).
  • In multivariate analysis (N = 225), having or not having seen the risk comparison, or the critique, made no significant difference to guilt or removal judgments
  • Participants who found the firm guilty were more often female (79% vs. 55%), and were also less educated, poorer, more likely to rent, less often white, and more likely to speak a language other than English at home
  • Those who found the firm guilty or wanted the asbestos removed were especially likely to believe that any exposure to a carcinogen will lead to cancer
• The authors' conclusion: The author concluded that risk comparisons in conflict situations are unlikely to have much effect. In the author's view, this is more because they do not shift views rooted in prior beliefs and social position than because they are vulnerable to criticism, and a simple 'inoculation' blocked the modest effect of the critique.
• Limitations the authors state:
  • A single replication for one hazard and one conflict scenario must be generalized cautiously
  • Sample sizes may have been too small to detect significant differences
  • The results may not apply to real jury decisions, because participants gave private individual judgments without group discussion
  • The inoculation effect may have come simply from having more arguments than the critique, rather than from its content

Topics

Medical terms in this study, explained in our Lexicon: Expert Witness.

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• Asbestos disease risk communication conducted by the New Jersey Department of Health — M. Stanbury, G. Solice-Sample, et al. (1993)
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