Errors and biases in

decision making process

Implications for public health

Aymery Constant

Maître de Conférences

Psychologie de la santé

Comparison of Risk in Health Care

With Other Industries

MODERATE RISK

MINIMAL RISK (<1/100,000)

HEALTH CARE

Bungee jumping

Driving

Chemical Manufacturing

Commercial Aviation

Nuclear Power

HIGH RISK (>1/1000)

Number of Encounters

Liv

es L

ost/

Year

Modified from R. Amalberti and L. Leape

Medical decision • Diagnoses

• Choosing a treatment?

• Initiate a new treatment? Keep the status quo?

• Death or disability?

• What’s the priority?

• Life? Well be? Freedom? Duty? Compassion?

Decision making

1) Logical and rational process

2) the Accumulation of knowledge improves the decision

3) Past experience improve judgment

4) collective decisions are more reliable

= MYTHS

Bounded Rationality

Case study

Ms. M., 62, visits her GP because she feels tired all the time and is

struggling to manage her daily activities.

Her GP ordered blood tests, that showed elevated levels of

transaminases (liver enymes)

He declared that she drinks too much alcohol and recommended

total abstinence. He talked about possible treatments, an hospitalization to

perform complementary medical exams (endoscopy, examination of the liver...),

and the possibility to join self-help groups.

Case study

= > Hepatitis C, she was infected during a sclerosis surgery ten years ago

HCV testing has been practiced several weeks after the initial

diagnosis, because Ms. M. finally convinced her GP to review his

diagnosis. Because she drinks very moderately

She was addressed to the Department of hepatology of the

University Hospital to start an antiviral treatment

No consequences (except the stress of being labeled as

alcoholic)

Where does the error comes from?

Lack of knowledge? Skills?

= > It is a graduated GP

Medical misinformation?

= > All medical data were valid

Lack of experience?

= > He works as a GP for decades

Lack of knowledge about the patient?

= > He was his family doctor for years

Hypotheses

High transaminase = alcohol abuse is the most readily

available diagnosis in memory?

May be that a large number of patients has a drinking

problem? And he made the connection with Ms. M.

Maybe he thought that the problem originated from

internal cause? Possible external causes were dismissed

He did not comprehensively seek all the relevant

information such as an invasive medical intervention 10 years

ago

He focused his attention on information confirming his

initial belief (alcoholism), ignoring those that refute it (no

clinical signs) or those who were in favor of others

hypotheses (chronic fatigue)?

Heuristic

Simplified cognitive strategy, used to save time,

allowing decision-maker to make acceptable

deductions

Evidenced by Tversky & Kahneman, in the 70s

Tversky, A. & Kahneman, D. (1974). Science, 185, 1124–1130.

Kahneman, D (1972). Judgment under uncertainty: Heuristics and biases.

Cambridge: Cambridge University Press.

Three of these heuristics are particularly influential:

- Availability

- Representativeness

- Anchoring

Availability

= > Estimating the likelihood of an event according to

its availability in memory.

The first impression or the most present explanation in mind is

used in priority to explain an event or estimate a probability..

According to a survey, 50% of Americans were affraid

of dying in a terrorist attack in 2006 (Gallup poll). The

probability of such an event was estimated at one

chance over 20 million (calculated on the basis of the

available figures)

Tversky, A; Kahneman (1973). "Availability: A heuristic for judging frequency and probability". Cognitive Psychology 5

(1): 207–233

A group of 100 persons, including 30 lawyers

and 70 engineers were interviewed. These

interviews have led to the drafting of brief

fact sheets on each of these people.

One of these cards was randomly chosen:

"John is 39 year-old. He is married and has two kids. He is involved in

local politics. His favorite hobby is the collection of rare books. He loves

competition, discussion and is an articulate speaker.

Representativeness

What is the probability that John is a lawyer?

Representativeness

Good answer: 30% (30 lawyers out of 100 persons)

But participants overestimated this proportion

because we tend to:

- Neglect probability and estimates. Individual or

descriptive information is preferred, in opposition to

mathematical logic.

- Focus on the supposed similarities between the

information (speaks well...) and our initial belief (he’s a

lawyer)

Anchoring

Participants were asked to estimate the percentage of African

countries members of the United Nations

Participants’ answer : 25% on average

Participants’ answer : 45% on average

• In the other group: "Is this more or less than 65%?"

• In a group: "Is this more or less than 10%?"

Anchoring

All the reasoning process is influenced by a

single initial data, which is difficult to ignore

afterwards

Explains the influence of first impressions, or those

of early learnings on decision making or situational

analysis

Cognitive Bias

Tendency to acquire and process information by filtering it

through one's own likes, dislikes, and experiences.

Relevant

Informations

Relevant

responses

Non relevant

informations

Non relevant

responses

Selection

bias

Reasoning

bias

Heuristics

Acad. Med. 2003;78:775–780

33 biases and heuristics reportedly active in medical practice

Information-gathering problems

Unpacking – failure to elicit all relevant information

Availability – recent exposure influences diagnosis

Anchoring – holding onto a diagnosis after receiving

contradictory information

Premature closure – accepting a diagnosis before it is

fully verified

Systems contributions

Diagnosis momentum – early diagnosis by

another provider is accepted as definite

Feedback sanction – final diagnosis does not

return to initial decision-maker

Triage cueing – location cues management (seen

through the lens of the first provider)

Probability Pitfalls

Aggregate bias – aggregate data do not apply to my patients

Base-rate neglect – ignoring the true prevalence

Gender bias – gender inappropriately colors probability

Gambler’s fallacy – sequence of same diagnoses will not continue

Posterior probability – sequence of same diagnoses will continue

Hypotheses High transaminase = alcohol abuse: most readily available

diagnosis in memory? Availability

May be that a large number of patients has a drinking problem?

And he makes the connection with Ms. M. Posterior Probability

Maybe he think it the problem originate from internal cause? And

not external? Attribution error

May he did not seek comprehensively all the relevant information

(invasive medical intervention it 10 years ago) Anchoring

=>Unpacking

Maybe he focused his attention on information confirming his initial

belief (alcoholism), ignoring those that refute it (no clinical signs) or

who were in favour of an others hypothesis (chronic fatigue)?

Interpretative bias

Emotions can jeopardize the rationality of

any decision maker

three types of affects:

- transitional: surrounding factors, fatigue...

- Due to personality: trait anxiety, emotional

adaptation

- Related to clinical situations: children

involved…

Affective bias

The best scientific evidence can be overlooked because of

affects, emotions….

“Our affective reactions to patients are often

our very first reactions, occurring automatically

and subsequently guiding information

processing, judgment, and decision making…”

Zajonc, American Psychologist, 1980

Two competing reasoning modes:

The first is fast, intuitive, automatic (or even

unconscious) often involves an affective or emotional

component, and requires few resources

=> satisfying responses

The second is analytic, slow, deliberate, affect-free

and costly in resources

=> Optimal responses

Most vulnerable

to biases

Bounded rationality:

Implications for public health

Some scientific information benefit from a large

consensus in the scientific community, the public

option, the media and health professionals

Strong Epidemiological evidence

high acceptance by the public and the media

health professionals practices

Public Health

Tobacco, alcohol abuse; unhealthy diet; drink

driving ….

Making relevant decisions regarding the health of

people suppose to be able to collect relevant

information

In ambiguous, new, changing unknowns, or

emotionally situations, the collection and

interpretation of the information will be influenced

by:

Information seeking

1) The way the information is presented

2) decison-makers’ initial beliefs

You are a top decision maker at WHO and you want take

preventive actions to reduce the number of deaths and

injuries from animal bites. On which animal will you

focus your intervention?

In Australia?

A) Dogs, B) Sharks, ou C) Crocodiles

In Romania?

A) Dogs, B) Sharks, ou C) Crocodiles

Public health

In South Africa?

A) Dogs, B) Sharks, ou C) Crocodiles

Framing The entire reasoning process is governed by the

way the information is presented

Chosen by 72% of participants

Chosen by 28% of participants

We expect that an epidemic will kill 600 people.

Participants are asked to choose between two

possible actions

Option A: can save the lives of 200 people

Option B: 33% chance of saving 600 people

Framing

Same scenario, different layout

Option A: 400 people will die

Option B: 33% chance that there is no death

Chosen by 22% of participants

Chosen by 78% of participants

The expected value is the same in both cases, but the statements

mentioning death are rejected, while those mentioning saved lives are

preferred

Framing

Tendency to Loss aversion: the negative value of a loss is

considered to be superior to an equivalent gain (capacity, life,

death…)

Outcome feeling

Gain of X Positive (+)

Loss of X Extremely negative

(---)

Framing

The framing allows to influence decision using

our tendency to loss aversion

If you are favorable to the LAMBDA treatment, you

will say to the patient:

"with the LAMBDA treatment, you have 90% chance of

survival.

If you prefer an alternative solution, you will say:

"with the LAMBDA treatment, you have 10% chance of

death”

Confirmation bias

Is organic food healthier? Can video games make kids violent? Is WI - FI carcinogenic?

=> Might cast a doubt, even in the absence of

scientific evidence

When faced with a closed (yes/no) question, we

naturally tend to seek confirming information to

answer “yes”

and then, ignore the alternative hypothesis

Confirmation bias

Exemple: Does Behaviour change during the full moon?

We will immediately remember some cases when we

were stressed, anxious, insomniacs or so…during full

moon nights…

….and forget the hundreds of full moon nights when

we slept normally

EHESP 35

Change the question

Open-ended Question : what are the risk factors for cancer?

- Tabacco - Alcohol - Unhealthy diet (sugar, fat…) - Sedentary behavior - Diesel - Sun exposure - ….

Changing mind?

...not an easy task

Interpretation bias

University of Santford (USA): Two groups of students are formed according to their opinions on death penalty: A group in favor of death penalty, and a group against the death penalty

Then two studies were presented: one demonstrating

the usefulness of death penalty, and one showing DP is

counter-productive

…And they are asked to assess the

methodological quality of these two studies

“Biased assimilation and attitude polarization: The

effects of prior theories on subsequently considered

evidence”

Conclusions regarding death penaly

« efficient » « counter-productive »

In favor of death

penalty Quality ++ Quality --

Conclusions regarding death penaly

« efficient » « counter-productive »

In favor of death

penalty Quality ++ Quality --

Against death

penalty Quality ++ Quality --

The studies are considered valid if they are in

line with personal opinions, and discredited

otherwise

“Biased assimilation and attitude polarization: The

effects of prior theories on subsequently considered

evidence”

Other effects

Media covering a political campaign will be considered hostile by both sides Lobbies will select studies which suit their own interest (bicycle helmet; adverse effect of a food or a drug benefit...) and ignore others studies Scientific work will be judged from political or ideological perspectives, regardless of actual scientific value (especially in social sciences…)

Case study from France

Rapport INSERM 2005

INSERM is the French institute for Health and Medecine Relying upon data from over a thousand international scientific studies, INSERM experts advocate in a 364-pages document (available online) to best inform parents and educators on conduct disorders in children and to detect it as soon as possible (3 years old), to ensure the prevention.

Conduct disorders (esp ADHD) are a major cause of unintentional injuries in children

http://www.ipubli.inserm.fr/bitstream/handle/10608/142/expcol_2005_trouble_synthese_eng.p

df?sequence=1

Recommandations from the report

Improving information on conduct disorder in France,

through epidemiological studies among children and

adolescents in the general population, as well as in high risk

populations

• Identify risk: family factors, pre - and perinatal, genetic.

• Develop specific prevention programs, train teachers and

educators, intervene with families at risk, track as soon as

possible warning signs, i.e. at the age of 3, and record

. Perform regular, accurate and multidisciplinary assessments

for subjects with symptoms.

Assess the effects of various psychotherapies. Further

pharmacological research.

Lobbying from French physicians

The very next day, the national Union of physicians of maternal and child welfare (SNMPMI), protested. Its leaders created a petition (available online) signed by nearly 200 000 Web users, along dozens of associations , psychologists, doctors, educators…. The first signatories include child psychiatrists, clinical psychologists, doctors, lecturers, childhood professionals,...... Many belonging to a lobby which pushed health minister to censor a report from INSERM in 2004 (namely

psychoanalysts…)

Online Petition

• "detected children would be subjected to a battery of tests

developed on the basis of the theories of behavioral

Neuropsychology" “According to the criteria of the Anglo-

Saxon studies"

• Nurseries and schools transformed into “hunting places',

• The potential offender , too small to defend himself, will

be transformed into a junkie

• "the slightest gesture, the first child nonsense may be

interpreted as the expression of a pathological personality

at the mercy of a "robotic health care thinking.

“http://www.pasde0deconduite.org/appel/

Framing: changing terms

Terms used in the

Report

Terms used in the online

petition

International studies « Anglo-saxons » studies

screening Hunting down

Identify risk factors and

prevent disorders

Relentless linearity principle

and deterministic approach

Early prevention Early hunt

Pharmacology as a second

line

Drug use

Psychotherapeutic support Behavioral conditioning

Interventions towards

families at risk

stigmatization

Children: high emotional bias

political context , cultural lobbies and ideological opinions

beliefs concerning the "Anglo-Saxon" (behaviorists)

use of international recommendations to change local

practices (esp those deriving from psycho-analysis)

Pétition: framing and loss

aversion

Discredit :

INSERM

"Anglos-Saxon"

Renowned experts

international studies

scientific recommendations

Achieved Result: statut quo

context

Change in practices

=

Fascism

Early screening and detection is

advocated for aged people

Past experience improve decison-making ?

Not sure….

Question # 1: "describe the exact content of the midday meal you took 15 days ago.

Memory bias

Question # 2: "describe the situation in which you were when you heard about the 9/11 attacks “

Recall is facilitated by emotions related to the

event: their presence (yes/no); their intensity

(high/low) and their nature (positive/negative)

“Dissociation of recall and fragment completion”

Journal of Abnormal Psychology, 101, 575–580

Memory bias

In the absence of mental health disorder, recalling pleasant memories is easier than recalling unpleasant ones

increased availability producing a memory bias

Our past experiences seem to be much more positive than they actually were

Memory bias Aims:

- mechanism of protection against depressed mood

("positive illusions"),

- justify aftermath decisions made during lifetime

("choice-supportive bias")

But: Any subjective reference to a past situation may

not be relevant to assess a present or predict a future

situation

And: Tend to reinforce resistance to change, anchoring

bias, perseverance of false beliefs, interpretation bias…

Is it possible to question ourselves ?

Fundamental attribution

error

Highlighted by Jones and Harris (1967) Participants were asked to judge essays written by students and defending ideological positions imposed by the teacher. Half of the participants knew that the ideological position was imposed, the other half thinking that students expressed their opinions

« The attribution of attitudes », 1967

Even participants who knew that the position was imposed considered that it reflected the true opinion of the writer Writers’ attitudes were estimated in line with the position they were forced to defend Overestimation of internal characteristics at the expense of possible external causes

Fundamental attribution error

Self serving bias

Following a misdiagnosed cancer in 1980, Mr. Paul Mongerson decided to create a company programming diagnosis software to help physicians In 2006, he asked his GP on the reasons why he did not use diagnosis software . - "it takes time and I do less than 1% error“ - “the literature shows that the error rate is 5-10%"

- "it is because of others physicians.“

The American Journal of Medicine (2008) Vol 121 (5A), fvii

Self serving bias

Gosling (1992) asked teachers on the cause of their students’ success and failure The results showed that: - when students succeed, teachers thought it was due to the quality of their teaching

- when students fail, they thought it was related to external causes (family context)

Qui est responsable de l’échec scolaire ? (1992 ) PUF, Paris

Reinforcing false beliefs:

Self fulfilling prophecies

September June

IQ test IQ test

Normal children intellectual bloomers

“Teacher Expectation for the

Disadvantaged”

Changes

Changes over a school year

All pupils labelled as “intellectual bloomers” improved their results significantly Better relationships were observed between these students and teachers Most important roles were attributed to spurters (keep the class, manage activities, etc.) Errors committed were minimized by teachers

Rosenthal effect

Children were labeled as “intellectual bloomers"or "normal" randomly

Rosenthal and Jacobson induced, for each child, either a “positive expectation” or “no expectation” among teachers

These expectations influnced teachers’ behaviors

towards each child, and academic outcomes….

…and confirmed the (falsified) IQ test !

A student was asked to call someone on the phone for some reason. A picture of the interlocutor was shown to him/her

Normal shape Overweight

(obese)

Sterotype : « obese persons are bad-tempered »

“Why does behavioral confirmation occur? A

functional perspective on the role of the perceiver”

Self-fulfilling prophecies

Those who called someone they believed to be overweight behaved in a most unpleasant way that those who called a person they believed to have a normal shape in return the person on the phone was also unpleasant with the caller => confirming the initial belief (again)

Snyder M, Haugen JA. 1994. Why does behavioral confirmation occur? A functional perspective on the role of the

perceiver. J. Exp. Soc. Psychol. 30:218–46

Prospective study on adolescent alcohol use

“Self-Fulfilling Prophecies : The Synergistic

Accumulative Effect of Parents' Beliefs on Children's

Drinking Behavior”

Adolescent alcohol use

Estimation by parents

Time 2

Adolescent alcohol use

12 months

Time 1

• Parents’ estimates similar to actual alcohol use

• overestimation

• underestimation

Higher alcohol

use

A study conducted in Britain, showed that the number of

emergency visits following a road accident was 52% higher on

Friday 13 as compared to Friday 6th, even though there were

fewer road traffic. The authors recommend to stay at home that

day

Scanlon, Luben, Scanlon, & Singleton, 1993

Is Friday the 13th bad for your health?

This student is an “intellectual bloomer”

obese persons are bad-tempered

my child drink a lot of alcohol

Friday the 13th is an unlucky day

Decisions, behaviors

expectations

Beliefs, sterotypes

Reactions and

consequences in line

with the expectations

Confirming

initial beliefs

« Placebo effect» Persistence of obsolete practices and false beliefs

Collective decision?

Beware! : Conformism

The ASCH Effect A group of students is asked to perform a simple vision test:

which line among the comparison line is like the standard one?

The ASCH effect

The group is composed of "accomplices", except one

student, who is the real subject of the experience

When accomplices unanimously support a wrong

answer, 37% of the subjects prefer to comply with

this false response rather than opposing the group

when the social pressure disappears, the correct response

rate reach 100 %

=>Normative social influence

=> Conformism

The ASCH effect

Fear to look ridiculous or silly, to be rejected (fear of

social disapproval)

= > Normative influence (conformism)

Not sure of its own response, lack of self confidence.

= > Informational influence

Informational influence is particularly important when someone

is faced with a task he does not control.

Normative influence is important when belonging to the group

is important

Obedience to authority figures

people obey orders from authority

figures: doctors, experts, scholar, intellectual,

etc. without asking neither the origin nor the

relevance of their statements

Bounded rationality

Why all these biases exist in the first place?

Because they give satisfactory results in familiars,

commons, routine situations and require few effort

=> adapted to the every day life situations

BUT: Adverse consequences for public health in

ambiguous situations: the discrediting of valid

knowledge, the persistence of false beliefs and obsolete

practices, status quo maintenance (resistance to change)

Counter measures:

From Bounded rationality to

critical rationalism

- Raise awareness of cognitive biases by information and

education, using concrete examples and detailed

descriptions of their potential effects

- Consider alternative hypothesis in any question.

- Take the step back from the immediate problem and

analyze it.

- Do not rely (too much) on memory

- - develop decision algorithms adapted to new situations

Critical rationalism

- Focus on information from several independent sources using rigorous and transparent methods to collect and analysis data (review of literature;)

- Make distinction between knowledge from science and knowledge from ideology, politics, religion (not evidence based)..

- The level of evidence contradicting an hypothesis must be at least equal to those confirming it, in order to cast a legitimate doubt

- As a decision maker, emotion is not your friend

EHESP 81

Nullius in Verba « words are nothing »

Motto of the Royal Society (London)