Presentation by Prof. George Gray, Director of the Centre for Risk Science and Public Health, George Washington University, at the Workshop on Risk Assessment in Regulatory Policy Analysis (RIA), Session 13, Mexico, 9-11 June 2014. Further information is available at http://www.oecd.org/gov/regulatory-policy/

1. Center for Risk Science and Public Health
Risk Perception and
Communication
George Gray
Center for Risk Science and Public Health
Department of Environmental and Occupational Health
Milken Institute School of Public Health

2. Center for Risk Science and Public Health
Risk Communication
• Risk communication is successful only to the extent that it
raises the level of understanding of relevant issues or
actions and satisfies those involved that they are adequately
informed within the limits of available knowledge.
• Risk communication is a component of risk management.
Successful risk communication does not guarantee that risk
management decisions will maximize general welfare; it
only ensures that decision makers will understand what is
known about the implications for welfare and the available
options.
Source: NRC-NAS (1989) Improving Risk Communication

3. Center for Risk Science and Public Health
Risk Communication
• A risk communication process that disseminates accurate
information is not successful unless the potential recipients
achieve a sufficient understanding. The recipient of the
information must be able to achieve a complete
understanding of the information he/she desires.
• Risk communication is more than one-way transmission of
expert knowledge to the uninformed. Messages about
expert knowledge are necessary to the risk communication
process; they are not sufficient, however, for the process to
be successful.
Source: NRC-NAS (1989) Improving Risk Communication

4. Center for Risk Science and Public Health
The Importance of
Risk Communication
• Inform people to make sound choices about risk
• Help build understanding for social efforts to
manage risks

5. Center for Risk Science and Public Health
Perceptions of
Environmental Quality
• Thinking about the nation as a whole, do you believe
that America’s air quality is better than, worse than, or
about the same as it was in 1970 when the Clean Air Act
was enacted?
• Better 29%
• Worse 38%
• About the Same 31%
• Don’t Know/Refused 2%
N=1000
Source: Foundation for Clean Air Progress

6. Center for Risk Science and Public Health
Air Quality Trends
According data from the U.S.
Environmental Protection Agency*
between 1970 and 2003:
• Nitrogen oxide emissions have
declined by 17%
• Sulfur dioxide emissions have
declined by 49%
• Lead emissions have declined by
98%
• Carbon monoxide emissions have
declined by 41%
• Volatile organic compounds have
declined by 48%,
• Particulate emissions from
combustion declined by 82%
*Source: http://www.epa.gov/airtrends
In the same period:
• U.S. population grew by 42%, to 291
million
• Overall energy consumption grew by
43%, to 97.351 trillion btu.
• Total U.S. employment grew by
95%, to 138 million.
• The number of registered vehicles
grew by 111%, to 235 million
• Annual Vehicle Miles Traveled
(VMT) grew by 151%, to 2.8 trillion
miles
• “Real” Gross Domestic Product
(GDP) grew by 175%, to $10.381
trillion.

7. Center for Risk Science and Public Health
What is Your Perception?
Q Which has caused more cancer deaths in the last 50
years?
Nuclear Radiation
The Sun
A Each year, just in the US, there are 1.3 million cases
of skin cancer, almost all from the sun. 7,800 people
die of melanoma each year. In 60 years since
Hiroshima and Nagasaki about 500 cancer deaths.
No other radiation release is linked to increased
cancer deaths, including TMI and Chernobyl
(although up to 4000 predicted by WHO)

8. Center for Risk Science and Public Health
What is Your Perception?
Q Which is responsible for a greater proportion of
human cancer?
Alcohol consumption
Environmental pollution
A The Harvard Center for Cancer Prevention
suggests alcohol responsible for 3% of human
cancer versus < 2% for pollution

9. Center for Risk Science and Public Health
Consequences of
Misperception of Risk?
• Influences efforts to protect self and family
• Sources of risk compete for attention and resources
• Diet
• Accidents (smoke detectors)
• Environmental risks
• Individuals play role in social decisions about risk

10. Center for Risk Science and Public Health
Factors Influencing Risk
Perception
Quantitative
Dimensions
How big is the risk?
How does it compare to other risks?

11. Center for Risk Science and Public Health
Science Matters
• Sound communication requires good information
• Size of a risk
• Sources of the risk
• Possible risk management options
• Decisions made solely on the basis of perception can
increase, rather than decrease, risk

12. Center for Risk Science and Public Health
Communicating Science

13. Center for Risk Science and Public Health
Factors Influencing Risk
Perception*
Qualitative
Attributes
What else do I know about the risk
that influences my perception?
* Throughout this presentation many examples are taken from 1) Kahneman,
Slovic and Tversky (1982); 2) Morgan and Henrion (1990) and 3) Ropeik, D.
(2010) How Risky Is It, Really?: Why Our Fears Don't Always Match the Facts.
McGraw Hill.

14. Center for Risk Science and Public Health
Thinking About Risk
• Biases and Heuristics – Making decisions under
uncertainty
• Risk Perception – How do we “feel” about risks?

15. Center for Risk Science and Public Health
Judgments Under Uncertainty
• When faced with uncertainty (risk) people rely on a
limited number of “rules of thumb” or heuristics in
making judgments
• Judgments under uncertainty may be subject to
manipulation through framing effects
• Heuristics often valuable and useful - but sometimes
mislead

16. Center for Risk Science and Public Health
Some Heuristics
• Representativeness
• Availability
• Anchoring and adjustment

17. Center for Risk Science and Public Health
Representativeness
• When judging the likelihood that an object (or idea)
belongs to a certain class, or is generated by a
certain process, people look for the characteristics of
the general class in the specific example
• Which is more likely result from 8 flips of a fair coin?
• H T H T T H T H
• H H H H T T T T

18. Center for Risk Science and Public Health
Representativeness
• Another bias related to representativeness is an insensitivity
to sample size.
A town is served by two hospitals. In the larger hospital
about 45 babies are born each day, and in the smaller about
15 are born. As you know, about 50% of all babies are girls.
However, the exact percentage varies from day to day.
For a period of one year, each hospital recorded the days on
which more than 60% of babies born were girls. Which
hospital do you think recorded more such days?
The Larger Hospital
The Smaller Hospital
About the Same (within 5% of each other)

19. Center for Risk Science and Public Health
Representativeness
• 95 undergraduates asked the hospital question
The Larger Hospital (21)
The Smaller Hospital (21)
About the Same (within 5% of each other) (53)
• Here, likelihood of a sample result is often judged by
the similarity to the overall population result
regardless of the size of the sample

20. Center for Risk Science and Public Health
Availability
• Occurs when people judge the probability of an
event by the ease with with they can recall similar
events
• Older people may overestimate the probability of
heart attacks because they can more easily recall
them in their circle of acquaintances
• Younger people may overestimate the probability of
car accidents which are more common with less
experienced drivers
• Botulism deaths more widely reported than strokes

21. Center for Risk Science and Public Health
Estimation of Annual
Fatalities

22. Center for Risk Science and Public Health
Availability
Other biases of availability:
• salience - stronger memory increases the judged
likelihood or recent events found more available than
past
• effectiveness of a search set - people often undertake
mental "search" to find relevant information.
"If I sample a random word (>3 letters) in the English
language, is it more likely that the word starts with r or
has r as the third letter?"
since it is easier to think of words beginning with r, most
respondents judge this more likely. It is not.

23. Center for Risk Science and Public Health
Anchoring and Adjustment
• People often form quantitative judgments starting
with a first value that is adjusted with supplementary
information.
• Anchors are often biased
• Adjustments are often too small

24. Center for Risk Science and Public Health
Anchoring and Adjustment
• People were asked to estimate the number of African
nations that are in United Nations.
• First, a wheel of fortune (with numbers from 1 to 100)
was spun in the subject's presence. Wheel designed
to always stop at either 10 or 65
starting point median estimate
10 25
65 45

25. Center for Risk Science and Public Health
Anchoring in Estimates of
Annual Deaths

26. Center for Risk Science and Public Health
Anchoring When Time is
Limited
• Please estimate within 5 seconds the result of the
following numerical expression:
Sample A 1 x 2 x 3 x 4 x 5 x 6 x 7 x 8
Sample B 8 x 7 x 6 x 5 x 4 x 3 x 2 x 1
• Median response
• Group A 512
• Group B 2,250
Correct answer - 40,320

27. Center for Risk Science and Public Health
The Classic
Perceived-Risk Model
Familiarity
High
High
Source: Slovic (1987)
Public
Outrage
Dread
Low
Low

28. Center for Risk Science and Public Health
What Influences Dread?
Fatal
Global Impact
Involuntary
Uncontrollable
Unfair
Catastrophic
Future
Generations
Increasing
Not Easily
Reduced
Not Fatal
Not Global Impact
Voluntary
Controllable
Fair
Individuals
Only Current
Generation
Decreasing
Easily Reduced

29. Center for Risk Science and Public Health
What Influences Familiarity?
Observable
Known to
Exposed
Immediate
Effect
Old Risk
Known to
Science
Not Observable
Unknown to
Exposed
Delayed Effect
New Risk
Unknown to Science

30. Center for Risk Science and Public Health
Other Factors
Man-Made
Children at Risk
Untrustworthy
Institutions
Media Focus
Identifiable Victims
Suppressed Data
Natural
Only Adults at Risk
Trustworthy
Institutions
Media Neglect
Statistical Victims
Accessible Data

31. Center for Risk Science and Public Health
Probability of Occurrence is
Not the Only Concern
not observable
unknown to those exposed
effect delayed/
new risk
risks unknown to science
observable
known to those exposed
effect immediate
old risk
risks known to science
controllable
not dread
not globally catastrophic
consequence not fatal
equitable
individual
low risk to future generations
easily reduced
risk decreasing
voluntary
uncontrollable
dread
globally catastrophic
consequence fatal
not equitable
catastrophic
high risk to future generations
not easily reduced
risk increasing
involuntary
Slovic, P. Science 236:280-285

32. Center for Risk Science and Public Health
RISK VS. BENEFIT?
• Vaccinations
• Artificial sweeteners
• Mammography and diagnostic X rays
• Prescription drugs
• Skiing

33. Center for Risk Science and Public Health
Lessons
Quantitative
Dimensions
Qualitative
Attributes
• People have difficulty making judgments
under uncertainty and use heuristics to help
• Many factors have been suggested to
influence perception but prediction is difficult

34. Center for Risk Science and Public Health
No Shortage of Risks

35. Center for Risk Science and Public Health
Why Does This Matter?
• We make judgments about personal risks every day
• Public views on risk influence social risk management
decisions
• There are real public health consequences to the
“risk perception gap”