Difference between revisions of "Decision theory"

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(Common abbreviations: rearranged the section, removed XDT (it's never discussed))
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*[http://lesswrong.com/lw/17b/decision_theory_why_pearl_helps_reduce_could_and/ Why Pearl helps reduce “could” and “would”, but still leaves us with at least three alternatives]
 
*[http://lesswrong.com/lw/17b/decision_theory_why_pearl_helps_reduce_could_and/ Why Pearl helps reduce “could” and “would”, but still leaves us with at least three alternatives]
  
==Common abbreviations==
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==Commonly discussed decision theories==
  
* CDT: [http://en.wikipedia.org/wiki/Causal_decision_theory Causal Decision Theory]
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Standard theories well-known in academia:
* EDT: [http://en.wikipedia.org/wiki/Evidential_decision_theory Evidential Decision Theory]
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* CDT, [http://en.wikipedia.org/wiki/Causal_decision_theory Causal Decision Theory]
* TDT: [[Timeless decision theory|Timeless Decision Theory]] (LW-only)
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* EDT, [http://en.wikipedia.org/wiki/Evidential_decision_theory Evidential Decision Theory]
* UDT: [[Updateless decision theory|Updateless Decision Theory]] (LW-only)
 
  
More rarely used:
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Theories invented by researchers associated with [[SingInst]] and LW, and frequently discussed on LW:
 
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* TDT, [[Timeless decision theory|Timeless Decision Theory]]
* ADT: [[Ambient decision theory|Ambient Decision Theory]]
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* UDT, [[Updateless decision theory|Updateless Decision Theory]]
* XDT: [http://lesswrong.com/lw/15m/towards_a_new_decision_theory/11jo?c=1 Exceptionless Decision Theory]
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* ADT: [[Ambient decision theory|Ambient Decision Theory]] (a variant of UDT)
  
 
==See also==
 
==See also==

Revision as of 07:16, 21 March 2012

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Decision theory is the study of principles and algorithms for making correct decisions—that is, decisions that allow an agent to achieve better outcomes with respect to its goals. Every action at least implicitly represents a decision under uncertainty: in a state of partial knowledge, something has to be done, even if that something turns out to be nothing (call it "the null action"). Even if you don't know how you make decisions, decisions do get made, and so there has to be some underlying mechanism. What is it? And how can it be done better? Decision theory has the answers.

A core idea in decision theory is that of expected utility maximization, usually intractable to directly calculate in practice, but an invaluable theoretical concept. An agent assigns utility to every possible outcome: a real number representing the goodness or desirability of that outcome. The mapping of outcomes to utilities is called the agent's utility function. (The utility function is said to be invariant under affine transformations: that is, the utilities can be scaled or translated by a constant while resulting in all the same decisions.) For every action that the agent could take, sum over the utilities of the various possible outcomes weighted by their probability: this is the expected utility of the action, and the action with the highest expected utility is to be chosen.

Thought experiments

The limitations and pathologies of decision theories can be analyzed by considering the decisions they suggest in the certain idealized situations that stretch the limits of decision theory's applicability. Some of the thought experiments more frequently discussed on LW include:

Blog posts

Sequence by AnnaSalamon

Commonly discussed decision theories

Standard theories well-known in academia:

Theories invented by researchers associated with SingInst and LW, and frequently discussed on LW:

See also