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ACT-R (most important assumption is that human knowledge can be divided…
ACT-R
most important assumption is that human knowledge can be divided into two irreducible kinds of representations: declarative and procedural.
declarative
represented in the form of chunks, i.e. vector representations of individual properties, each of them accessible from a labelled slot.
collection of chunks that contain few elements that are linked together through spreading activation-->highly active chunks are kept in short- term memory and rest in long- term memory
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Prodecual: encoding of information in environment ; Declarative: enoding of objects in the environment
Knowledge units:from large database are selected for particular context by activation processes tuned to structure of environment
KNOWLEDGE IS MADE AVAILABLE ACCORDING TO ITS ODDS OF BEING USED IN A PARTICULAR CONTEXT-->MIND KEEPS TRACK OF GENERAL USEFULNESS AND COMBINES THIS WITH CONTEXTUAL APPROPRIATE TO MAKE SOME INFERENCE ABOUT WHAT KNOWLEDGE TO MAKE AVAILABLE TO CONTEXT
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activation level: being appropriate in the current context; base level: odds that has been useful in past; contextual priming: likelihood that it will be useful in given context
Running a model automatically produces a step-by-step simulation of human behavior which specifies each individual cognitive operation
memory encoding and retrieval, visual and auditory encoding, motor programming and execution, mental imagery manipulation
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Goal stack vs. current goal allows to focus the attention of the ACT- R on what it is currently trying to do
Goal Stack: items are pushed onto a stack and popped from a stack, according to the current goal> no limit number of goals
Systems adopt a goal- directed approach taking a current goal & current state and acting to achieve the goal or adding a new goal that needs to be completed first
current goal is undertaken & all future goals are stored on a goal stack (= a bit of memory where things can be put in and gotten out again but only in reverse order: last in – first out)
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other goals that are not in immediate focus of attention, but still need to be dealt with sometime later
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ACT-R is a framework: for different tasks (e.g., Tower of Hanoi, memory for text or for list of words, language comprehension, communication, aircraft controlling)
create "models" (i.e., programs) in ACT-R. These models reflect the modelers' assumptions about the task within the ACT-R view of cognition. The model might then be run
ACT-R has also been extended to make quantitative predictions of patterns of activation in the brain
augmented to predict the shape and time-course of the BOLD response of several brain areas, including the hand and mouth areas in the motor cortex, the left prefrontal cortex, the anterior cingulate cortex, and the basal ganglia
aims to define the basic and irreducible cognitive and perceptual operations that enable the human mind.
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language primitives and data-types are designed to reflect the theoretical assumptions about human cognition