CMSC 491M/691M - Spring 2003

Discussion Questions for Class #3, February 3

Reading Guidelines:

• Start with the brief overview (HTML page)
• Look through the tutorial; it's a little hard to follow, since it's just a presentation without context, but will give you a flavor of what an ACT-R model looks like.
• Read the longer Anderson et al. paper, skipping over the detailed discussion of brain structure (p. 8)  and the differences between ACT-R 4.0 and 5.0 (pp. 10-11), and skimming lightly over the perceptual-motor system (pp. 11-15).  Also, in general, you can gloss over the detailed descriptions of the cognitive experiments, since we are primarily interested in ACT-R as a computational model, rather than its accuracy as a cognitive model.

Questions:

• What's a cognitive architecture?
• What does ACT-R stand for?
• What are the "serial bottlenecks" in ACT-R?  Why do you think Anderson et al. chose to place these restrictions on the architecture?
• Production rules are the fundamental component of cognitive reasoning in ACT-R.
• What's a production rule?
• How are production rules triggered?
• What is the mechanism for resolving conflicts between competing competitions?
• How are the conflict-resolution weights learned?
• What is a chunk in ACT-R?
• How are chunks activated?
• What are the components of activation level?
• What is meant by spreading activation?
• What does Anderson mean by symbolic vs. subsymbolic processes?
• How do production-rule abstraction and goal structuring enable the use of the ACT-R production rule system to model very complex cognitive behaviors such as planning?
• Describe some domains that you think ACT-R would be especially well suited for.
• Describe some domains that you think ACT-R would not be well suited for.
• Do you think that ACT-R is a good model of human cognition?  Why or why not?
• Do you think that ACT-R is a good model to use for implementing artificial cognition?  Why or why not?
• Be prepared to discuss the justifications that Anderson gives for ACT-R's architectural choices in contrasting ACT-R with other approaches (in the final section of the paper). We will be revisiting these tradeoffs later in the semester as we study other architectures!