From social psychology to sociology - a physicist’s point of view

Katarzyna Sznajd-WeronInstitute of Theoretical PhysicsWrocław University

Praha, November 6, 2003

Plan

Can we explain global changes by microscopic models?

Can we treat people like particles?Examples of social experiments.Social psychology and sociology.A simple model.

Almost a century ago physicists asked the question:

Can phase transitions be explained by microscopic theory?

T

M

T*

ferromagnet paramagnet

Back to 1920 ...

Wilhelm Lenz proposed a very simple microscopic model of interacting spins.

0

1

,

J

ShSSJH

S

ii

jiji

i

Was it only hope?

i

ii

ii ShSSJH 1

Spontaneous magnetization cannot be explained using this model in its 1D version.

After two decadeshope became reality

Onsager showed that the 2D version of the model can explain the critical phase transition.

Very simple local interactions can lead to qualitative changes on the macroscopic scale.

T

M

T*

The hope outside Physics

Rapid changes on macroscopic scale appear

in various systems.

Mostly these changes are unexpected.

Usually there is no obvious reason for them.

Can we explain them in terms of microscopic

interactions like we did for physical systems?

People sometimes behave like particles

Conformity The Millgram experiment:

Obedience to Authority The Asch experiment:

peer pressure Social validation

Conformity - Obedience to Authority

The consequences of nonconformity

Stanley Millgram: Obedience to Authority (Yale, 1961-62)

Stanley Milgram (1973) Journal of Abnormal and Social Psychology

volts learner experimenter

90 Ou! Please continue

105 Ou! (lauder) It is essential that we continue....

120 Ou! It hurts! Continue, it’s necessary

135 Ou! It is really painful The experiment requires that you go on until he has learned all the word pairs correctly

150 Let me leave! My heart ...

You have no other choice

What will happen? – ask psychiatrists and psychologists

Predicted: most subjects would not go beyond 150 volts, when the victim makes his first explicit demand to be freed.

Only 4% would reach 300 volts.

Only a pathological fringe of about 0.1% would use the highest shock on the board.

Results of the Millgram experiment

Solomon E. Asch - a pioneer of social psychology

Solomon E. Asch, born in Warsaw in 1907, he came to the United States in 1920 and received a Ph.D. from Columbia University in 1932.

Experiment of conformity (without Authority), 1956

Asch(1951-1955) – the experiment on visual perception?

The experimenter asks to choose which of the three lines on the left matches the length of the one on the right.

Results of the Asch experiment: social pressure

76% conformed to the majority at least once.

Conformity became more frequent as group size increased.

“The tendency to conformity in our society is so strong that reasonably intelligent (...) people are willing to call white black” /Asch/

There are some limits ...

1 2 3 4 5 6 7 8 9 100%

10%

20%

30%

40%

Number of people against

Mis

take

s

The power of social validation

Milgram, Bickman & Berkowitz, 1969

Results of experiments: 1 4%, 5 80%

Robert B. Cialdini: Social Validation –

the fundamental way of decision making

Social validation can cause trouble

BANK

From social psychology to sociology

Social PsychologyFundamental unit:A person(micro scale)

SociologyFundamental unit:A social group(macro scale)

Social opinion

Sociologists ask if it will be better in the future?

09.97 06.98 04.99 02.00

-0.5

0

0.5

Time

YE

S-N

O

Social Norm: The ratio between breast and waist (Vogue)

1910 1930 1950 1970 1990

1.2

1.4

1.6

1.8

2B

W

B/W

Year

78/60

100/60

From micro to macro scale ...

Person = Spin (element of the system)Social validation = interaction between

elementsSocial opinion = magnetization

A model based on social validation

YES = +1 NO = -1

What to do if you do not know what to do ...

Whatever (financial market)

Nothing (Stauffer et al.)

„United we stand divided we fall” (original rule)

How does it work?

A sample simulation

0 20 40 60 80 100

0

10

100

1000

10000

Voters

Nu

mb

er

of

sim

ula

tio

n

ste

ps

Evolution of the system: social opinion (Yes-No)

N

iiSN

m1

1

1

m

0.5

Time

What has happened?

0 20 40 60 80 100 1200

2

4

6

8

10

12

14

time interval (100 MCS)

num

ber

of d

ecis

ion

chan

ges

We follow one person ...

100

101

102

103

10-4

10-2

100

102

P(

)

simulationspowerfit -1.5

Characteristic time of opinion change does not exist!

100

101

102

10310

0

102

104

106

108

Waiting time

Dis

trib

utio

n

What happens if we sometimes turn off the auto-pilot?

121

1

1 ,1

iiii

p

ii SSSSSS

There is some external field in every social system

For h=1h

1

-1

Advertising: with probability |h| buy product sgn(h).

0 0.2 0.4 0.6 0.8 1Power of advertisement (h)

Pro

babi

lity

of “

conq

uerin

g”

the

mar

ket

0

0.2

0.4

0.6

0.8

1

c0=0.05

c0=0.15

c0=0.25

Who wins ?

Generalized model - two components (TC)

Dynamics - the information flows outwardsDisagreement function - the change of

spins is controlled by function, which locally is minimized:

11211 iiii SSJSSJF

Possible transitions

21 JJ 21 JJ 21 JJ 21 JJ

0

0

22121

212121

JJJJJ

JJJJJJUSDF

Phase diagram for 1D TC model

1

J2 0

-1-1 0 1

J1

TC model in 2D

Phase I(1,2,3,4)

Phase 3(5,6)

Pha

se 2

(1)

Pha

se 4

(2)

-1 0 1 J1

1

J2 0

-1

1 2

3 4

5 6

Phase diagram for 2D TC model

You never know which state you will reach …

J1=1, J2=2

How to predict the future?

21 JJ 2J 2J 21 JJ 1/8 1/2 1/4 1/8

Local agreement – global disagreement

0 500 1000 1500 2000 2500 3000-6

-5.5

-5

-4.5

-4

-3.5

-3

-2.5

-2

-1.5

time (MCS)

disa

gree

men

t fun

ctio

n

Social norm as an external field?

Social opinion

Social norm

Time to say „goodbye”