Appendix
P9-6

TIEMS 2014 Annual Conference

Clarifying Effect of Biases on Evacuation Behavior in Disaster＊University of Hyogo,＊＊The Daiei, Inc.

Airi TAKAHASHI*,Kazuhiro HIGUCHI*,Miki MATSUMOTO*,Chiharu MIYAKE*,Yukari MORIYAMA*,Kota TOMOYASU*,Reo KIMURA*,Akane MIURA**

Background ・ Methods

Various biases retard evacuation behavior in disasters.
We can’t evacuate quickly in disasters. Because we fall
into various biases such as normalcy bias and conformity
bias that hinder evacuation behavior.
We clarified the relationship between biases and types ofdisasters using data set.
The purpose of research is to clarify relationship between
biases and types of disasters in research. We picked out
111 personal disaster experiences from 53 documents.
And we made data set to clarify the relationship between
personal disaster experiences and biases.

The Relationship Between Biasesand Disasters

We tested chi-squared test based on cross tabulationtables according to the types of disasters and biases.
We clarified a tendency that various biases distort ourcongnition in evacuation behavior.
Comparatively
Disorientation Normalcy bias optimism bias Veteran bias

Virgin bias

Intraplateearthquakes

Conformity
Optimism bias bias

…We tend to fall into biases.
（Significant at the 1% level）…We tend to fall into biases.
（Significant at the 5% level）…We do not tend to fall into biases.
（Significant at the 1% level）

Subduction-zone
earthquakes
TsunamiStorm and flood
disasters＊The blank means no significant differences.

Biases in Earthquake

We tend to fall into disorientation in intraplate earthquake.
Intraplateearthquake(n=17)The others(n=94)The rate of people who
fall into disorientation

100%
7.4%

020

Χ²(1)＝72.7, p＜.01
406080100 (%)

When an intraplate earthquake occurs, the groundshakes strongly and the surrounding of us changes greatly.
Therefore, we cannot grasp our surrounding and ourstatus accurately.
Countermeasures
It is possible for us to recover from disorientation if wehave knowledge that disorientation happens in intraplate
earthquake and we simulate accurate behavior
concretely before earthquake.

ううWe tend to fall into normalcy bias in subduction-zone
earthquakes.
The rate of people who
Subduction-zone
67.4%
earthquake(n=46)
The others
27.7%(n=65)
02040

fall into normalcy bias

60

80 (%)

Χ²(1)＝17.2, p＜.01

When subduction-zone earthquake occurs, the groundshakes. But shaking is slowly. So, we tend to assume that
we are in normal situation in spite of being in risky situation.
As a result, we don’t make disaster responses.
Countermeasures
We should understand “earthquake-tsunami association”.
As soon as you encounter an earthquake, we should
recall tsunami, and evacuate higher and farther placefrom the sea immediately.

352

Biases we tend to fall in disasters(Biases mean cognitive prejudice)
Name of biases

Meaning
We cannot grasp our surrounding and our status accurately when the surrounding of us
changes greatly.
We tend to regard aberration as normal because we want to assume that we are in safety
Normalcy bias
situation.
Comparatively We tend to regard believe that disasters never occur in our residential area by no conclusive
optimism bias evidence in comparison with other places.
When we consider ourselves as a veteran or an expert in disaster, we tend to overconfidence
Veteran bias
our abilities in risk perception, judgment or response about disasters.
Disorientation

Virgin bias

We tend to overestimate or underestimate of risks when we have no experience it.

We tend to overestimate positive information. On the other hand, we tend to underestimate
negative information.
When our own opinion, judgment or behavior is different from those of the majority in group
Conformity bias
we belong to, we tend to change our opinion, judgment or behavior to match with majority's.
Optimism bias

Biases in Storm and Flood Disasters
We tend to fall into virgin bias in storm and flooddisasters.
The rate of people who
Storm and flood
39.3%
disasters(n=28)
The others
14.5%(n=83)
01020

fall into virgin bias

30

40

50 (%)

Χ²(1)＝7.9, p＜.05

We have no experience flood disaster, but we haveexperience heavy rain several times. Even if heavy
rain falls, we underestimate possibility of disasteroccurrence.
We tend to fall into optimism bias in storm and flooddisasters.
The rate of people who
Storm and flood
disasters(n=28)

The others
10.8%(n=83)
0

fall into optimism bias

28.6%

10

Χ²(1)＝5.1, p＜.05
2030 (%)

We don’t think heavy rain cause flood disasters.
Countermeasures
We have to associate disaster occurrence withheavy rain. And then, we get information about
heavy rain and prepare for disaster.

Suggestion
We have to know the relationship between biases
and disasters.
Types of biases we tend to fall in vary depending on
the types of disasters. Therefore, we have to take into
account that different biases for each disasterobstruct our appropriate disaster responses. Once wefall into biases, it takes long time to complete
evacuation behavior after we recognize hazard
information. We suggest “packaging decision-makingprocess” is effective way to shorten time when we
take evacuation behavior.
Packaging Decision-Making Process
Equipping the package ofDecision-making process(cognize risks quickly, decide Cognition Decision Behavior
response appropriately andbehave darling evacuation
Quick Appropriate Accurateaccurately) , we can makedisaster response without thinking.

Journal of Disaster Research Vol.10 No.2, 2015