From social psychology to sociology - a physicist’s point of view Katarzyna Sznajd-Weron Institute of Theoretical Physics Wrocław 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* ferromagnetparamagnet

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

Was it only hope? Spontaneous magnetization cannot be explained using this model in its 1D version.

After two decades hope 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, )

Stanley Milgram (1973) Journal of Abnormal and Social Psychology voltslearnerexperimenter 90Ou!Please continue 105Ou! (lauder)It is essential that we continue Ou! It hurts!Continue, it’s necessary 135Ou! It is really painfulThe experiment requires that you go on until he has learned all the word pairs correctly 150Let 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 Experiment of conformity (without Authority), 1956

Asch( ) – 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 % 10% 20% 30% 40% Number of people against Mistakes

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 Psychology Fundamental unit: A person (micro scale) Sociology Fundamental unit: A social group (macro scale)

Social opinion Sociologists ask if it will be better in the future? Time YES-NO

Social Norm: The ratio between breast and waist (Vogue) B W B/W Year 78/60 100/60

From micro to macro scale... Person = Spin (element of the system) Social validation = interaction between elements Social 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 Voters Number of simulation steps

Evolution of the system: social opinion (Yes-No) 1 m 0.5 TimeWhat has happened?

We follow one person...

Characteristic time of opinion change does not exist!

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

There is some external field in every social system For h=1 h 1 Advertising: with probability |h| buy product sgn(h).

Power of advertisement (h) Probability of “conquering” the market Who wins ?

Generalized model - two components (TC) Dynamics - the information flows outwards Disagreement function - the change of spins is controlled by function, which locally is minimized:

Possible transitions USDF

Phase diagram for 1D TC model 1 J J1

TC model in 2D

Phase I (1,2,3,4) Phase 3 (5,6) Phase 2 (1) Phase 4 (2) J1 1 J Phase diagram for 2D TC model

You never know which state you will reach … J1=1, J2=2

How to predict the future? 1/81/21/41/8

Local agreement – global disagreement time (MCS) disagreement function

Social norm as an external field? Social opinion Social norm

Time to say „goodbye”