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Realistic Psychosocial Behaviour
in Non Player Characters
Reading Course by Christine Bailey
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Overview NPC psychology
Typical NPC control architectures Social Science
Relevant social computing research
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NPC Psychology Cognition
Thinking
Emotion
The sum of past events
Many many different models possible
Categorical vs. dimensional
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Typical NPC Control Actors vs. Agents
The usual suspectsactor control
General agent architectures
Specialized agent architectures
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Actors or Agents? Actors
Not autonomous
Actions are scripted/hard-coded Actors are directed
Agents
Autonomous
Not hardcoded Not rigidly directed
Some NPCs can be both via switching
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NPC Control in Games - Actors Usually:
FSMs (i.e. for state of mind)
Scripting for behaviour
All states and transitions must be defined a
priori
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Agent Architectures Reactive/Reflex
Triggering
Internal stateself-awareness & memory
Goal-based
Preferred states
Goal importance: First-come, first-served
Also, no plan preference
Utility-based
Utility-value on goals, plans
Anytime
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Agent Architectures All of these have cognition
Only utility-based has emotion (non-
arbitrary plan-selection)
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Emotion as decision-making According to Damasios studies of people
with brain damage:
If cognition and emotion are separated,
decision-making cannot occur in a non-
arbitrary fashion
Cognition=plan-generation Emotion=plan-selection (non-arbitrary)
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Specialized Agent Architectures Soar
H-CogAff
EXCALIBUR
being-in-the-world
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Soar Utility-based
Some components:
Learning, knowledge, goals
Preference list
So, this is an architecture that considersemotion
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H-CogAff Anytime-based
Several layers:
Reactive (quick responses)
Deliberative (goal-based)
Meta-management (learning)
Also: Personality module
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EXCALIBUR Anytime-based
Concerns:
Incomplete knowledge planning
Resource needs
Temporal scheduling
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being-in-the-world Hybrid architecture
Real-time coping
Perception & Reaction
Knowledge base
Plans -> actions
Reasoning
Plan generation
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Specialized Agent Architectures One of the architectures has emotion (Soar)
One even has personality (HCogAff)
But none of these architectures really
consider social systems
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Social Science NPCs should consider social stimuli as
well as physical stimuli when making
decisions
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An overview of the social stuff Attitudes:
Faking it with reputation systems
Remembered interaction histories
Change of attitude
Group influences:
The flow of opinion
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An overview of the social stuff Social roles, world view, etc.:
A high level architecture for believable social
agents
An attempt to integrate mood, personality,
& social networks:
Realistic Reaction System
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Gimme some attitude Faking it with reputation systems
Remembered interaction histories
Change of attitude
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Reputation Systems i.e.Fable, Thief: Deadly Shadows, Ultima
Online,
NPC opinions of player
No opinions about other NPCs
No individual opinions (sometimes groups) Immediate and global
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Reputation Systems Note that this is only faking a social
system
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Remembered Interaction
Histories Tomlinson & Blumberg (2002)
Every new interaction with a stimulus
changes the way we feel about that
stimulus
So says Damasios Somatic Marker
Hypothesis
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Remembered Interaction
Histories Key elements
Current emotional state
Current object of interest
Emotional memory (per object)
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Remembered Interaction
Histories Each new interaction, current emotional
state changes:
NPCs current emotional state
Remembered emotional memory
On interaction end, remembered emotional
history is updated:
Factor in the emotional state during
interaction
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Attitude Change Prendinger & Ishizuka (2002)
Attitude: a disposition to like/dislike
something (or someone, or some place, )
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Attitude Change Attitude affected by:
Previous attitude
Weight of emotional events
Recency of emotional events
Current events
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Events that conflict with previous
attitude? Momentary vs. Essential like/dislike
Momentaryevent is integrated with
previous attitude
Essentialevent replaces previous attitude
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The influence of the group Opinion flow
Peoples opinions are not static they may
change depending on new events, peer
opinions, etc.
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Opinion flow as flock Cole (2006)
Combines:
Social Network Analysis
Boids algorithm
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Social Network Analysis (SNA) Nodes
Ties
Hubs
Nodes w/ high number of ties
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Attack of the Boids The Boids algorithm
Alignment (steer towards avg. heading)
Cohesion (move to avg. position)
Separation (avoid crowding)
Field of vision
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Opinion flow as a flock Alignmentsteer opinion towards avg.
group opinion
Cohesionsteer opinion towards avg.
opinion of people of respect
Separationsteer opinion away from avg.
opinion of people of contempt
Field of visiontie connectivity score
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Cool, dynamic changes of
opinion In real life, people groups change their
opinions
i.e. groupthink, conformity,
Most simulated environments: everyone
has static opinions/beliefs
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Social roles, world view, etc. A high level architecture for believable
social agents
Social roles, social roles, social roles!
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A high level architecture for
believable social agents Guye-Vuilleme & Thalmann (2001)
Social roles:
A coherent set of standard behaviours (plans)
Multiple exist in single individual
Are a way of adapting to a situation
Can inherit from other social roles (i.e. woman,
mother)
Are associated with other social roles (i.e. mother,
father)
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A high level architecture for
believable social agents Role switching through activation energy
Role activation energy associated with:
Initial role weight
Locations
Times
Locality to associated roles (i.e.mother/father)
Role energy can also be inhibited
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A high level architecture for
believable social agents Values
pursuit of an ideal abstract state (because I
am honest.) A classifying criteria (because hes a
crook.)
Action-selection based on being right, not
being successful
World viewvia own interests, integratedvalues, norm-based behaviour
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A high level architecture for
believable social agents Cognitive module
Active role?
Belief generation
Social reasoner
selects behaviour by weighing beliefs/values
Type identifiers
Inference engine, world view
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Integrating psychology and social
networks The Realistic Reaction System
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The Realistic Reaction System
(RRS) Gruenwoldt, Katchabaw, & Danton (2005)
Integration of:
Personality
Mood
Social relationships
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The RRS Elements:
AI Controller
Personality/Mood Filter
Relationship Network
Relationship Manager
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The RRS Social ties have:
Type
History
Regularity
Strength
Polarity
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Summary NPC Psychology
Cognition & Emotions
NPC control Actors, Agents,
Social Science
Relevant social computing research Attitudes, group influences, social roles, world view,
etc., integrating mood, personality, & social networks
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The End Questions?