Risk Perception and Communication

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


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


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


The Importance of Risk Communication

•  Inform people to make sound choices about risk

•  Help build understanding for social efforts to manage risks


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


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.


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)


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


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


Factors Influencing Risk Perception

Quantitative Dimensions

How big is the risk? How does it compare to other risks?


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


Communicating Science


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.


Thinking About Risk

•  Biases and Heuristics – Making decisions under uncertainty

•  Risk Perception – How do we “feel” about risks?


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


Some Heuristics

•  Representativeness

•  Availability

•  Anchoring and adjustment


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


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)


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


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


Estimation of Annual Fatalities


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.


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


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


Anchoring in Estimates of Annual Deaths


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


The Classic Perceived-Risk Model Familiarity

High

High

Source: Slovic (1987)

Public Outrage

Dread

Low

Low


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


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


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


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


RISK VS. BENEFIT?

•  Vaccinations •  Artificial sweeteners •  Mammography and diagnostic X rays •  Prescription drugs •  Skiing


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


No Shortage of Risks


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”

Risk Perception and Communication

Government & Nonprofit

public health

public health

risk communication

public health

risk communication

observable

risk science

adjustment