Risk perception mechanisms

Risk perception mechanisms lay behind the fact that subjective risk perception deviates from objective risks. What people perceive, is real for them; so their behaviour will be influenced not by the actual level of security, but of their perception of it. Citizens always assess risks, threats and uncertainties on a subjective and individual basis. To a certain extent, gaps between felt and factual risks/security are normal phenomena.

Factors affecting human risk percpetion

Factors that affect citizens' perception of risk are variable and complex. Risk research, independent of the subject matter in question, sees citizens’ assessment of risks and threats considerably dependent on knowledge of precedents, frequency and extent of risk experience as well as perceived immediate effects on themselves.

The following listing summarizes factors that affect citizens' perception of risk and felt need for public authorities to address risk:

• Voluntariness: Risks from activities considered to be involuntary or imposed (for example, exposure to chemicals and radiation from a terrorist attack using chemical weapons or dirty bombs) are judged to be greater, and are therefore less readily accepted, than risks from voluntary activities (such as smoking, sunbathing or mountain climbing).
• Controllability: Risks from activities considered to be under the control of others (such as the release of nerve gas in a coordinated series of terrorist attacks) are judged to be greater, and are less readily accepted than those from activities considered to be under the control of the individual (such as driving an automobile or riding a bicycle).
• Familiarity: Risks resulting from activities viewed as unfamiliar (such as travel leading to exposure to exotic-sounding infectious diseases) are judged greater than risks resulting from activities viewed as familiar (such as household work).
• Fairness: Risks from activities believed to be unfair or to involve unfair processes (such as inequities in the location of medical facilities) are judged greater than risks from “fair” activities (such as widespread vaccinations).
• Benefits: Risks from activities that seem to have unclear, questionable or diffused personal or economic benefits (for example, proximity to waste-disposal facilities) are judged to be greater than risks resulting from activities with clear benefits (for example, employment or automobile driving).
• Understanding: Poorly understood risks (such as the health effects of long-term exposure to low doses of toxic chemicals or radiation) are judged to be greater than risks that are well understood or self-explanatory (such as pedestrian accidents or slipping on ice).
• Uncertainty: Risks that are relatively unknown or highly uncertain (such as those associated with genetic engineering) are judged to be greater than risks from activities that appear to be relatively well known to science (such as actuarial risk data related to automobile accidents).
• Effects on children: Activities that appear to put children specifically at risk (such as drinking milk contaminated with radiation or toxic chemicals or pregnant women exposed to radiation or toxic chemicals) are judged to carry greater risks than more-general activities (such as employment).
• Victim identity: Risks from activities that produce identifiable victims (such as an individual worker exposed to high levels of toxic chemicals or radiation, or a child who falls down a well) are judged to be greater than risks from activities that produce statistical victim profiles (such as automobile accidents).
• Dread: Risks from activities that evoke fear, terror or anxiety due to the horrific consequences of exposure (for example to HIV, radiation sickness, cancer, Ebola or smallpox) are judged to be greater than risks from activities that do not arouse such feelings or emotions regarding exposure (for example to common colds or household accidents).
• Trust: Risks from activities associated with individuals, institutions or organizations lacking in trust and credibility (for example, chemical companies or nuclear power plants with poor safety records) are judged to be greater than risks from activities associated with trustworthy and credible sources (for example, regulatory agencies that achieve high levels of compliance from regulated industries).
• Ethical and moral status: Risks from activities believed to be ethically objectionable or morally wrong (such as providing diluted or outdated vaccines for an economically distressed community) are judged to be greater than the risks from ethically neutral activities (such as the side-effects of medication).
• Catastrophic potential: Risks from activities associated with potentially high numbers of deaths and injuries grouped in time and space (for example, major terrorist attacks using biological, chemical or nuclear weapons) are judged to be greater than risks from activities that cause deaths and injuries scattered (often apparently randomly) in time and space (for example, household accidents).
• Media attention: Risks from activities that generate considerable media attention (such as anthrax attacks using the postal system or accidents at nuclear power plants) are judged to be greater than risks from activities that generate little media attention (such as occupational accidents).
• Accident history: Activities with a history of major accidents or incidents, or frequent minor accidents or incidents (such as leaks from waste-disposal facilities) are judged to carry greater risks than activities with little or no such history (such as recombinant DNA experimentation).
• Reversibility: The risks of potentially irreversible adverse effects (such as birth defects from exposure to a toxic substance or radiation) are judged to be greater than risks considered to be reversible (for example, sports injuries).
• Personal stake: Activities viewed as placing people or their families personally and directly at risk (such as living near a waste-disposal site) are judged to carry greater risks than activities that appear to pose no direct or personal threat (such as the disposal of waste in remote areas).
• Human versus natural origin: Risks generated by human action, failure or incompetence (such as negligence, inadequate safeguards or operator error) are judged to be greater than risks believed to be caused by nature or “acts of god” (such as exposure to geological radon or cosmic rays).

Relevance for security-related urban planning

The general mechanisms of human risk perception summarized above can for example help indentify urban objects that citizens perceive as insecure and/or under high risk. Apart from physical security of urban environment, urban planning needs to be aware of and address citizens' perception of (in)security and risks.