What is ACT-R? What is ACT-R? Declarative and Procedural Knowledge Declarative and Procedural Knowledge The ACT-R Architecture The ACT-R Architecture Examples for Modules Examples for Modules Summary Summary What is ACT-R? 1 Unified Theory of Mind Requirements Domains Cognitive Modeling Declarative and Procedural Knowledge 2 Lecture 3: ACT-R Declarative Knowledge Procedural Knowledge The ACT-R Architecture 3 Frank Keller Modules Architecture School of Informatics Processing University of Edinburgh keller@inf.ed.ac.uk Examples for Modules 4 Declarative Memory January 31, 2005 Procedural Memory Summary 5 Reading: Anderson (1996) Frank Keller Cognitive Modeling 1 Frank Keller Cognitive Modeling 2 What is ACT-R? What is ACT-R? Declarative and Procedural Knowledge Unified Theory of Mind Declarative and Procedural Knowledge Unified Theory of Mind The ACT-R Architecture Requirements The ACT-R Architecture Requirements Examples for Modules Domains Examples for Modules Domains Summary Summary A Cognitive Architecture A Unified Theory of Mind A single system (mind) produces all aspects of behavior, even if ACT-R provides “some important new insights into the made up of parts. We need a theory that gives the whole picture. integration of cognition” (Anderson 1996): Argument for integration and application: it is a unified theory of cognition realized as a production better for tackling applied problems, which are less feasible if system; only isolated research programs are addressed. it is designed to predict human behavior by processing information and generating intelligent behavior itself; Example it integrates theories of cognition, visual attention and motor Learning mathematics involves: understanding mathematical movement; expressions, reading, language processing (instructions and word it successfully models high-level cognitive phenomena, such as problems), spatial processing, problem solving, reasoning and skill working memory, scientific reasoning, skill acquisition, HCI. acquisition. Frank Keller Cognitive Modeling 3 Frank Keller Cognitive Modeling 4
What is ACT-R? What is ACT-R? Declarative and Procedural Knowledge Unified Theory of Mind Declarative and Procedural Knowledge Unified Theory of Mind The ACT-R Architecture Requirements The ACT-R Architecture Requirements Examples for Modules Domains Examples for Modules Domains Summary Summary Example: Salvucci and Macuga (2001) Requirements for Cognitive Architectures Understand environment in which human cognition occurs, and Predicts effect of cell phone use on driving . Aim: predicting results, perceptual and motor access to that environment: not just fitting results to experimental data: 1 the environment is not constrained (as in an experiment): developed separate ACT-R models of driving and of using a robust behavior is needed to deal with errors, the unexpected cell phone; and the unknown; put these together to predict effects of driving on cell phone 2 the importance of a priori predictions. use, and of phone use on driving. Model fitting criticized: belief that parameter estimation permits Compared four ways of dialing ⇒ good predictions. fitting to any pattern of data. Effect on driving (swerving) ⇒ only the full manual dialing condition has significant impact. “Rather than just predicting results or estimating parameters to predict quantitative predictions the ideal model should predict Note: did not estimate parameters to fit data – had no data – used absolute values without estimating parameters” (Anderson 2002). established ACT-R parameters. Frank Keller Cognitive Modeling 5 Frank Keller Cognitive Modeling 6 What is ACT-R? What is ACT-R? Declarative and Procedural Knowledge Unified Theory of Mind Declarative and Procedural Knowledge Declarative Knowledge The ACT-R Architecture Requirements The ACT-R Architecture Procedural Knowledge Examples for Modules Domains Examples for Modules Summary Summary Domains of ACT-R Models (examples) Declarative and Procedural Knowledge ACT-R: cognition emerges as the result of interaction between 1 Perception and Attention: visual search; eye movements; procedural and declarative knowledge. task switching; driving behavior; situational awareness. Declarative knowledge: factual, holds information; represents 2 Learning and Memory: list memory; implicit learning; skill things remembered or perceived. acquisition; category learning; arithmetic; learning by Example exploration and example. “2 + 2 = 4”, “Edinburgh is the capital of Scotland”. 3 Problem Solving and Decision Making: use and design of artifacts; spatial reasoning; game playing; insight and scientific Procedural knowledge: encodes processes and skills necessary to discovery. achieve a given goal: production rules that fire when conditions satisfied and executes specified actions. 4 Language Processing: parsing; analogy and metaphor; learning; sentence memory; communication and negotiation. Example 5 Other: cognitive development; emotion; individual differences. IF goal is to add two digits d 1 and d 2 in a column and d 1 + d 2 = d 3 THEN set as a subgoal to write d 3 in the column. Frank Keller Cognitive Modeling 7 Frank Keller Cognitive Modeling 8
What is ACT-R? What is ACT-R? Declarative and Procedural Knowledge Declarative and Procedural Knowledge Declarative Knowledge Declarative Knowledge The ACT-R Architecture The ACT-R Architecture Procedural Knowledge Procedural Knowledge Examples for Modules Examples for Modules Summary Summary Declarative Knowledge Procedural Knowledge Procedural knowledge can be decomposed into conditions and Basic units of declarative knowledge are chunks. They might actions. represent: Conditions: situational awareness, “there is a car to my right”; navigational knowledge, “Princes Street intersects with North may depend on declarative knowledge (i.e., recall of a chunk) and/or sensory input from environment; Bridge”; a specification of the goal and a number of chunks; driver’s goals and intentions, “pick up friend at the corner”. often test the contents of buffers. Chunks defined by types (categories) + slots (attributes): Actions: 1 “the dog chased the cat”: type chase , slots are agent (dog) and object (cat); can alter declarative knowledge, change goals, or initiate 2 “4 + 3 = 7”: type addition-fact , slots addend1 , addend2 , and motor actions in the environment; sum . produce changes in the contents of buffers. Frank Keller Cognitive Modeling 9 Frank Keller Cognitive Modeling 10 What is ACT-R? What is ACT-R? Declarative and Procedural Knowledge Declarative and Procedural Knowledge Modules Declarative Knowledge The ACT-R Architecture The ACT-R Architecture Architecture Procedural Knowledge Examples for Modules Examples for Modules Processing Summary Summary Procedural Knowledge Modules in ACT-R Modules devoted to: Example identifying objects in the visual field; controlling the hands; IF current goal is to encode a distant perceptual point for steering retrieving information from declarative memory; (test of goal) and there is a tangent point present (i.e., a curve) keeping track of current goals and intentions. (test of contents of visual system) Central production system: THEN shift attention to this point and encode its position and distance (build a visual representation) not sensitive to activity of modules, but responds to information deposited in buffers of these modules; each module makes this available as a chunk in a buffer. Frank Keller Cognitive Modeling 11 Frank Keller Cognitive Modeling 12
What is ACT-R? What is ACT-R? Declarative and Procedural Knowledge Modules Declarative and Procedural Knowledge Modules The ACT-R Architecture Architecture The ACT-R Architecture Architecture Examples for Modules Processing Examples for Modules Processing Summary Summary Particular Modules Modules and Brain Regions 1 Goal buffer: associated with the dorsolateral prefrontal cortex (DLPFC): keeps track of internal state in solving a problem. 2 Retrieval buffer: associated with ventrolateral prefrontal cortex (VLPFC): holds information retrieved from long term declarative memory. 3 Two visual buffers: associated with dorsal “where” path of the visual system and ventral “what” system: keep track of visual objects and their identity. 4 Manual buffer: associated with motor and somatosensory cortical areas controlling and monitoring hand movement: responsible for control of the hands. Frank Keller Cognitive Modeling 13 Frank Keller Cognitive Modeling 14 What is ACT-R? What is ACT-R? Declarative and Procedural Knowledge Modules Declarative and Procedural Knowledge Modules The ACT-R Architecture Architecture The ACT-R Architecture Architecture Examples for Modules Processing Examples for Modules Processing Summary Summary ACT-R: Organization of Information ACT-R Operates in Real Time Each covert step of cognition or overt action has latencies associated based on psychological theories and data. Critical cycle in ACT-R in which: the buffers hold representations determined by the external world and internal modules; patterns in these buffers are recognized and a production fires; buffers then updated for another cycle. Assumption in ACT-R is that critical cycle takes about 50 ms: estimate emerged, e.g., in SOAR (Newell 1990). Frank Keller Cognitive Modeling 15 Frank Keller Cognitive Modeling 16
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