Introduction to AI
1990’s – Agents
10 November 2010
0 Rational agent concept from economy.
0 Utility theory: the theory of preferred outcomes.
0 Decision theory: the dynamics of utility maximization
in an unpredictable environment.
0 Game theory: the dynamics of utility maximization
when participants affect each other’s utility in a
0 Perceive the environment through sensors.
0 Act on the environment through actuators.
0 The environment can be non‐physical.
0 Percept: the set of perceptions at some point in time.
0 Percept sequence: the set of a perception‐time pairs.
0 Agent function: percept sequence action
0 Agent program: an implementation of an agent
0 Agent architecture
0 A rational being considers all the consequences of all
possible actions, and makes these consequences part
of the decision processes for performing each of those
0 Given an environment and a percept sequence, what is
the ‘best’ thing to do?
0 Performance measure: objective assessment of the
value of success of an arbitrary environment
1. Prior knowledge of the agent.
2. Performance measure of environment state
3. Possible actions the agent can perform.
4. Percept sequence of the agent.
0 Information gathering: performing (3) in order to
enrich (4) and thereby increase (1).
0 Learning: increase (1) through (4).
0 Autonomy: all of (1) relates back to (4).
Inputs to deliberation:
0 Current percepts
0 State: model or internal representation.
0 Condition‐action rules.
0 Recent actions.
0 The state is updated based on previous state, most
recent action, and percept.
0 The action is chosen based on state and rules.
0 Swarm intelligence: performance measure applied to
0 Decentralized representation
0 Emergent behavior
0 Weak emergence: the qualities of the system are
reducible to the system's constituent parts.
0 Strong emergence: e.g. qualia.
0 The concepts of utility and rationality change!
Prisoner B silent Prisoner B betray
Prisoner A silent A:0.5, B:0.5 A:10, B:0
Prisoner A betray A:0, B:10 A:5, B:5
Two suspects are arrested. If one testifies against the other (betray) and
the other remains silent, the betrayer goes free and the silent accomplice
receives the full 10‐year sentence. If both remain silent, both prisoners
are sentenced to only six months for a minor charge. If each betrays the
other, each receives a 5‐year sentence. How should the prisoners act?
• No matter what the other player does, a player will always
gain a greater payoff by playing defect.
• Since in any situation betraying is more beneficial than
remaining silent, all rational players will betray.