Violence Risk Assessment and Risk Communication: The Effects of Using Actual Cases, Providing Instruction, and Employing Probability Versus Frequency Formats
Paul Slovic, John Monahan and Donald MacGregor mailed case summaries of hospitalised psychiatric patients to members of the American Academy of Psychiatry and Law and asked them to estimate each patient's chance of harming someone within six months of discharge and to rate the risk as high, medium or low. Response scales that distinguished finely among small probabilities led clinicians to rate patients as less likely to cause harm. Asking for relative frequencies instead of probabilities, or giving clinicians instruction, did not remove the effect. Frequency scales produced lower average likelihood estimates overall, yet at the same likelihood level frequency-based estimates signalled higher risk. Describing dangerousness as a frequency made risk seem much greater than an equivalent probability did, which the authors attribute to the more vivid and alarming imagery that frequencies evoke.
Paul Slovic, John Monahan and Donald MacGregor mailed case summaries of hospitalised psychiatric patients to members of the American Academy of Psychiatry and Law and asked them to estimate each patient's chance of harming someone within six months of discharge and to rate the risk as high, medium or low. Response scales that distinguished finely among small probabilities led clinicians to rate patients as less likely to cause harm. Asking for relative frequencies instead of probabilities, or giving clinicians instruction, did not remove the effect. Frequency scales produced lower average likelihood estimates overall, yet at the same likelihood level frequency-based estimates signalled higher risk. Describing dangerousness as a frequency made risk seem much greater than an equivalent probability did, which the authors attribute to the more vivid and alarming imagery that frequencies evoke.
Written from the abstract read 2026-10-22 via the National Criminal Justice Reference Service record.
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Slovic, P., Monahan, J., & MacGregor, D. G. (2000). Violence Risk Assessment and Risk Communication: The Effects of Using Actual Cases, Providing Instruction, and Employing Probability Versus Frequency Formats. Law and Human Behavior, 24(3), 271-296. doi:10.1023/A:1005595519944