Transcript Swarm Intelligence: Humans — Actual, Imagined and Implied

Humans – Actual, Imagined & Implied
From Swarm Intelligence by Kennedy Et. Al.
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March 11, 2003
Hridesh Rajan
Before We Begin…
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This chapter is a survey of psychological and
sociological efforts relating it to swarm
behaviors in some ways.
In “my opinion” the author did not relate well
bits and pieces of the loosely bound sections of
this chapter to the main theme of the book.
I have almost “NO” background in psychology
and sociology.
Hridesh Rajan
March 11, 2003
Roadmap
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Behavioral psychology to cognitive psychology.
Simulating social influence.
Culture.
Hridesh Rajan
March 11, 2003
Behavioral Psychology
BEHAVIORAL PSYCHOLOGY is the subset
of psychology that focuses on studying
and modifying observable behavior by
means of systematic manipulation of
environmental factors.
From: www.killology.com/article_behavioral.htm
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Behaviorist’s Doctrine
Classical conditioning
- Organisms passively
react to events in the
environment.
- Organism pushed by
the stimuli.
[Pavlov]
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Operant conditioning
- Organisms act on the
environment to obtain
a reinforcement.
- Organism pulled
towards a stimulus.
[ Watson, Hull and Skinner]
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From Behavioral To Cognitive
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Cognitive Psychology
Stimuli
Human
Response
There is more to human behavior than just stimuli and
responses.
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How Are Stimuli and Response
Related?
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How to explain why small rewards had greater
effect?
How to explain variation in problem solving
time?
How to explain social learning?
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March 11, 2003
Vicarious Reinforcement
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Learn a task without actually doing it.
Key is to watch someone else do it.
“Bobo doll” experiment. [Bandura 1962].
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Further on the Cognitive Way
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Gestalt process.
Lewin’s field theory.
Sociocognitive efforts in parallel to behavioral
and cognitive psychologists.
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March 11, 2003
Gestalt’s Prägnanz /Good Form
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Tendency to organize perceptions into
coherent wholes.
Permits partitioning the environment into
recognizable objects.
These objects can now be processed to
generate responses, whereas it was not
possible to process the environment.
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Lewin’s Field Theory
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Life space consists of individuals.
Individuals denoted by bounded regions.
They act upon others and are acted upon.
A person can be divided into number of
separate but interconnected regions.
An environment can be divided into number of
separate regions.
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March 11, 2003
Lewin’s Field Theory
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A person can be part of another person’s
environment (society).
A person can move through the life space,
which is called locomotion.
Regions that are interconnected influence each
other and this can cause locomotion to achieve
equilibrium.
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Social Influence
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[Sherif 1936] experiment showed that the
individual behavior tend to drift towards the
norm of the group.
[Asch 1965] showed a similar result of peer
pressure with human confederates.
[Crtutchfield 1955] and [Deutsch and Gerard
1955] used automated confederates.
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March 11, 2003
Sociocognition
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Thinking is a social activity.
Coordinated cognitive activities evoke
intersubjectivity(shared understanding).
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Social Aspects to Memory
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Transactive memory: using people you know
well as references to encode, store and
retrieve memories. [ Dan Wegner at UVA]
Content: past social actions and experiences.
Symbolic communication.
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Introducing Simulations as
Evaluation strategy
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Simulating Social Influence
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Inability to distinguish between a phenomenon
and a simulation of the phenomenon.
Making edible sculpture of food.
Simulating mind.
Imitative social behavior.
Induced compliance paradigm [ you are free to
do what ever you wish, but if I were you …].
Hridesh Rajan
March 11, 2003
Prisoner’s Dilemma[AxelRod 84]
Two player competition or co-operation.
 Both co-operate -> high payoff.
 Both compete -> low payoff.
 One compete other co-operate, competing
players payoff is high whereas co-operating
players payoff is abysmally low.
[This was the first computer experiment widely
accepted by social psychologists].
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Solutions
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TIT-FOR-TAT (Winner)
TIT-FOR-TWO-TATS.
LOOKAHEAD
DOWNING (Simulates behavior seen in human
subjects in the situation).
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Hutchin’s Network
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Each person is represented as a parallel
constraint satisfaction network.
Positive interconnection of a node of such
network to corresponding node of other
network signifies belief communication.
Hutchin’s example had two globally optimal
solution.
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Hutchin’s Network
Positive Link
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Negative
Link
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Hutchin’s Network Results
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When the nodes are highly connected, it
results in sub-optimal pattern. (Striking
similarity to social influence results.).
When the nodes are isolated, nothing special.
When the nodes are moderately connected
optimal pattern is reached.
Hridesh Rajan
March 11, 2003
Inferences
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Moderate ignorance not only permits cognitive
consistencies, but agreement among members
of a group.
“..We are always in a negative state of
knowledge, ignorance.”
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Culture
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Coordination Games
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Prisoner’s dilemma revisited.
Game of chicken
Battle of the sexes
El Farol problem
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Game of Chicken
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Choices
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Swerve
Stay on the Road
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El Farol Problem [Arthur 1994]
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N people decide independently to go to the bar.
Optimal situation: present <= 0.6 * population.
Choices are unaffected by previous visits; there is no
collusion or prior communication among the agents.
Only information available is the numbers who came in past
weeks.
There is no deductively rational solution--no "correct"
expectational model.
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El Farol Problem
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Each of the agent can form k hypotheses of the
form [f(present1,…,presentn) => present0].
Each agent decides to go or stay according to
the currently most accurate predictor in his set.
Once decisions are made, each agent learns
the new attendance figure, and updates the
accuracies of his monitored predictors.
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El Farol Problem
From: http://www.santafe.edu/arthur/Papers/El_Farol.html
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Sugarscape[Epstein & Axtell]
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Artificial society emulator.
- Seeded with population, an environment and
rules.
- Can be used to test whether certain
phenomenon of economics are necessary
outcomes of dynamic principles.
- What parameters affect the pattern of
observed behavior?
Hridesh Rajan
March 11, 2003
An Epidemiological Model in
Sugarscape
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Germs are coded as bit strings of length 5
example: 10110.
Immune system of an agent is coded as bit
string of length 50.
If disease agent bit string is a sub-string of
immune system bit string agent is immune to
that disease.
Hridesh Rajan
March 11, 2003
An Epidemiological Model in
Sugarscape
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Agents are allowed to propagate genetically,
evolving immune system.
Fitness function: how well does the immune
system protects agents from diseases in the
population.
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An Epidemiological Model in
Sugarscape
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Disease are spread from agent to agent when
they interacted.
An interesting observation was that the
immune system could evolve that was shorter
than the sum of lengths of antigen it guarded
against.
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ACE [Tesfatsion]
Key observation:
“ In the real world people choose whom to talk
with, whom to interact with, whom to do
business with, ..”
 Objective of the project is to understand how
coordination arises in decentralized systems.
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Competing-Norms Model [Picker 97]
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One kind of behavior might remain prevalent
even if a superior behavior is available.[e.g.
people doing dangerous things, ignoring
threats, starving themselves in the name of
beauty.]
It is not easy to enforce laws that contradict
popular ways of doing things.[ American drug
prohibition]
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Mutable Prisoner’s Dilemma
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An individual agent is represented as a cell in
CA and it plays repeated games with the the
members of its payoff neighborhood.
An individual agent also belongs to an
information neighborhood, with whom it
gathers feedback about their strategies and
success.
Choice of strategy is randomly assigned for the
first round.
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Results
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Populations almost always converge to a
unanimity.
Usually they converge on the best strategy, but
when the relative benefit fall below threshold or
when the initial best population was too low,
the population converged on the inferior
choice.
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Inference
By just communicating in the local
neighborhood it is possible to optimize even a
very complex decision function.
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Total Strength
Ringelmann Effect [Ringlemann 1913]
Number of People
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Dynamic Social Impact Theory
[Latane 1981]
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Probability of any individual helping someone
in need decreases as number of people
present increases. [ With John Darley]
Group influence is proportional to the strength,
immediacy, and the number of group members.
Polarization: Individuals in a population
resemble their neighbors, whereas regions of
population differ from each other.
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Dynamic Social Impact Theory
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Consolidation- the diversity of opinion reduces as
individuals are exposed to a preponderance of majority
arguments.
Clustering- people become more similar to their
neighbors in social space.
Correlation- attitudes that were originally independent
tend to become associated.
Continued diversity - clustering protects minority views
from complete consolidation.
Hridesh Rajan
March 11, 2003
Evolutionary Culture Model
[Boyd and Richerson 1985]
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Some part of the human behavior is
determined by genetics, on the other hand, our
genes predisposes us to behave socially in a
way that results in culture.
Much of our behavior is acquired by imitation,
through a process called cultural transmission.
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March 11, 2003
Evolutionary Culture Model
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When is individual learning more adaptive?
Environment is relatively homogeneous and stable
over time so that generalization is possible.
When is social learning more adaptive?
Environment is diverse and each time an individual
samples it, different results are obtained, so individual
can only attain a comprehensive view by learning from
other’s experience.
Hridesh Rajan
March 11, 2003
Types and Aspects of Cultural
Transmission
Basic facts:
- Genotype is the genetic coding of an organism.
- Phenotype is the expression of the genotype.
- Phenotype develops through the interaction of the
genes with the environment.
- Some phenotypes are more variable than others.
- Some phenotypes depend more on the environment for
expression; e.g. phenotype freckles do not appear
unless the person spends some time in sun.
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Boyd and Richerson’s Observation
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Human phenotype expression of behavior depends on
two type of learning – learning derived from cultural
norms that the person is exposed to and the learning
acquired through individual experience.
Upon evolution, individual’s adaptations - and their
subsequent probability of survival and reproduction –
depended jointly on their individual experience and on
what they learned from society.
Further tendency to learn more in one way or the other
was also genetically evolved.
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March 11, 2003
Without a Culture
“A man who has been alone since birth will have
no verbal behavior, will not be aware of himself
as a person, will possess no techniques of self
management, and with respect to the world
around him will have only those meager skills
which can be acquired in one short lifetime
from nonsocial contingencies.. To be for
oneself is to be almost nothing.”
– Skinner 1971.
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