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Lecture

LEC2 – The Search Inference Framework Sept 17 2009?


Department
Psychology
Course Code
PSY370H1
Professor
John Vervaeke

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PSY370: Thinking and Reasoning
LEC2 The Search Inference Framework
Sept, 17th, 2009
Review from last Lecture
! thinking is altered by our psycho/cultural technology
! normative theory is generated by logical rationalization and not empirical evidence
Dominant Framework: Search Inference Framework
! comes out of the computation tradition
! thinking is a form of information processing
! information processing is best understood as computation
! Newell & Simon 1957 are the founding fathers of this tradition
! an opponent of the Gestalt tradition
! problem solving consists of the search through a search space/problem space
! Baron did an influential review of this in 1994
! we search for 3 kinds of things
1. search for possibilities
! possible answers to the questions/problems at hand
2. goals
! we wonder what our goals are unlike animals
! functioning as criteria against which you can evaluate possibilities
! goals need to be formulated in such a way that they can help us distinguish and
choose b/w possibilities
3. evidence
! belief or potential belief that helps you determine how well a possible answer can
actually achieve a goal
! inference is the use of evidence to alter belief
! we can alter belief about our possibilities, goals and previous evidence
! judgement: the evaluation of the interconnections b/w goals and possibilities
! formal way of problem solving such that it can be solved computationally
! a problem is formally represented by 4 kinds of elements
! 1. description of initial state
! 2. description of goal state to be achieved
! 3. set of operators
actions that can be taken which can be taken to change the current state of the problem
! 4. path constraints
impose on addition constraints on the solutions beyond simply reaching the goal
! ie. find a solution in the fewest possible steps
! this is an abstract space
! it consists of all possible states that can be reached by applying the operators
! A solution is a sequence of operators that can transform the initial state to the goal state while
obeying the path constraints
! a problem solving method is a procedure for finding a solution
! F^D
! F = # of operators available to you at any step
! D = # of steps you have to go through
! Chess
F = 30 legal moves
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