Evolutionary Health
Co-Evolution of Disease & Living Conditions
Health Effects
What is Risk?
Environmental Risk
Risk Assessment
Risk Abatement
Risk Perception
Risk Management
Uncertainty & Other Features of Risk Assessment
Precautionary Principle
Appendix 1: Contaminants
Appendix 2: Environmnet & Reproductive Health
Internet Links
Other Resources
Health & Risk System PDF
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Risk Perception

Experiments conducted by psychologists reveal that individuals have a difficult time determining the relative risks in many activities. We also often have a hard time ranking the frequency of many causes of death, because some “exposures, shcuh as floods and motor vehicle accidents are catastrophic and highly publicized while other types of causes such as obesity and diabetes are chronic, and are not as obvious causes of death. Further experiments also show that we are often overconfident in our ability to predict risks.

The individual strategy to estimate risk is called "heuristics.” A "heuristic" is a simple set of rules based on information available to an individual (information that is often based upon experience, or "trial and error") that he or she then uses to make decisions or estimations about a given situation. Two of the main heuristics we use in estimating risk are the availability heuristic and the anchoring and adjustment heuristic.

The availability heuristic simply means that people determine the probability of an event occurring by how easily they can recall or imagine examples of the occurrence of a similar event. A good example of the availability heuristic in action is how one overestimates the deathes by bee sting and cancer and underestimates those from diabetes.

People's feelings about exposure to a risk are also strongly influenced by whether they chose to expose themselves to that risk. For example, a smoker who accepts the risk of her smoking habit might react strongly to the risk of dioxins leaching from tampons and creating the risk of cervical cancer. She may take precautions in this case, even though the risk is smaller than that from smoking.

The objective behind risk assessment is to get a "number" that could be used objectively to determine impacts. However, we discussed all the problems involved with the assessment particularly the DRA. In addition, the risk you calculated is for a generic population. Although, Can you answer the question of "will I get cancer if I live next to this risk?," Or, "am I safe?" No you can't answer those questions definitively. In a democratic society, people have a say in their exposure to chemical risks. Therefore, it is important to understand something about how people perceive risk.

The public’s assessment of risk may be markedly different from quantitative risk assessment using collected data. Several reasons for this discrepancy include:

  • Memorable events alter perception. Media articles, lots of deaths occurring at one time, sudden deaths occurring (airline crash, student shooting spree)
  • Population risk versus individual risk alters perception- uncertain as to who will be the 1 in a million. People still play the lottery hoping to be that 1 in a million or even 1 in 10 million.
  • Immediacy of talking about risk influences public perception of risk and that perception may change over time (media, surveys)
  • Human beliefs change slowly despite evidence to the contrary
  • The way information is presented affects public perception (risk of death is 32% versus risk of survival is 68% say the same thing but can lead to different perceptions)
  • Voluntary versus involuntary risks cause different reactions from the public. Often it is okay to choose a risk but it is not okay for government or industry to put me at risk
  • Natural versus artificial risk are often viewed differently even if the risk is the same (spices versus pesticides)





  ©Copyright 2003 Carnegie Mellon University
This material is based upon work supported by the National Science Foundation under Grant Number 9653194. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.