In Dan Gardner’s excellent Risk, he lists psychologist Paul Slovic‘s list of 18 factors that influence how we judge the severity of risk:
- Catastrophic Potential If fatalities would occur in large numbers in a single event — instead of in small numbers dispersed over time — our perception of risk rises.
- Familiarity Unfamiliar or novel risks make us worry more.
- Understanding If we believe that how an activity or technology works is not well understood, our sense of risk goes up.
- Personal Control If we feel the potential for harm is beyond our control — like a passenger in an airplane — we worry more than if we feel in control — the driver of a car.
- Voluntariness If we don’t choose to engage the risk, it feels more threatening.
- Children It’s much worse if kids are involved.
- Future Generations If the risk threatens future generations, we worry more.
- Victim Identity Identifiable victims rather than statistical abstractions make the sense of risk rise.
- Dread If the effects generate fear, the sense of risk rises.
- Trust If the institutions involved are not trusted, risk rises.
- Media Attention More media means more worry.
- Accident History Bad events in the past boost the sense of risk.
- Equity If the benefits go to some and the dangers to others, we raise the risk ranking.
- Benefits If the benefits of the activity or technology are not clear, it is judged to be riskier.
- Reversibility If the effects of something going wrong cannot be reversed, risk rises.
- Personal Risk If it endangers me, it’s riskier.
- Origin Man-made risks are riskier than those of natural origin.
- Timing More immediate threats loom larger while those in the future tend to be discounted.
For more on risk perception, you can do worse than peruse the Wikipedia entry.