Task 3 Flashcards
What is ACT-R?
= adaptive control of thought
a computer program that mimics human behaviour
-> is isolated from the external world
main components:
1. goal stack
2. current goal
3. procedural memory
4. declarative memory
5. outside world
What is declarative memory?
- the things we know as facts
- a collection of chunks that contain a number of elements
What is a chunk?
- declarative memory elements
- each main row of chunks holds a value in a different slot
- each chunk has a level of activation (= spreading information) -> not constant
= a lot of activation - easy and quick to retrieve -> STM
= low activation - hard to find -> LTM
= no activation - effectively forgotten until activation level rises
What is procedural memory?
- thinks we know how to do
- learned as production rules
= different representations and goals - stores procedures that have a condition (= if) and an action (= then) part
What is retrieval request?
- connection from procedural to declarative memory
- production rule fired in procedural memory may require elements from the declarative memory
What is production compilation? (+What are stages of learning production rules?)
- from declarative to procedural memory
- new production rules can be created in procedural rules from chunks in declarative memory
- stages of learning production rules
- understanding
- production compilation
- practice
What is the goal stack ?
consists of goals that are not the immediate focus of attention, but that still need to be dealt with in the future
(= warteliste)
-> based on last-in-first out (LIFO)
-> goals can be pushed (added) or popped (removed)
-> can be criticised for its lack of psychological plausibility
what is the current goal?
- focus of current attention
- representing what ACT-R is currently processing
What are memory phenomena of ACT-R?
- list memory
= experimental paradigm used to inderstand how things are stored in and recalled from STM - forward recall
- backward recall
- free recall
What is the primacy effect?
accuracy is the highest for the first elements in the list
-> participants rehearse the first elements of the list during the presentation of the other elements
What is the recency effect ?
accuracy is the highest for the last elements in the list
-> last elements are still accessible from memory during recall phase (= activation level has not decayed)
What does an ACT-R model have to do to accurately reflect empirical data?
- Have a representation of how items are chunked in declarative memory
- Have production rules for the rehearsal of items and retrieval from memory
- Model activation levels and show how they affect recall accuracy and latency
What are production rules ?
- condition part
> retrieval from declarative memory (= function of activation level that matches the condition; the higher the easier) - action part
-> similar to the action performed by a turing machine in a single step
What is SNIF-ACT?
- scent based navigation and information foraging in the ACT architecture
- developed to stimulate users as they perform unfamiliar information-seeking tasks on WWW
- it selects actions based on the measure of information scent
> calculated by a spreading activation mechanism that caputures mutual relevance of the contents of the webpage to the goal of the user
what are the main predictions and results of SNIF-ACT?
- link following behaviour:
users working on unfamiliar tasks are expected to choose links that have high information scent - Points at which users will give up on WWW sites:
when the information scent of the site diminishes below a certain threshold
results:
current content based spreading activation SNIF-ACT model can generate useful predictions about complex user-WWW interactions
what is the association strength ?
- strength of the bond between an item and the required chunk
- influences the flow of activation between chunks
- depends on the total number of associations
- If an item is only associated with one chunk, this chunk receives the full associative strength of the item = the full effect of any activation
What is the fan effect?
- applies to list memory
- the greater the number of facts related to some concept that a subject has to memorize, the slower the subject will be to recall any one of them.
- explained through limited capacity of association strength
What is an the activation threshold?
- a chunk that falls below the activation threshold is unavailable for retrieval by the production rules
- The activation level affects recall success.
- ACT-R specifies the relationship between activation and latency = the weaker the activation, the slower the recall process
- partial matching is possible
> important in positional confusion (= transportantion errors)
What are auxiliary and architectural assumptions?
auxiliary: decisions on how to deal with flexibility
architectural: general claims to the nature of human cognition
advantage of ACT-R:
all assumptions are made explicit
How does the user tracing method work?
- two tasks
> Antz Task
> City task (= easier) - tracing instrumentation:
> Weblogger (= tracking keystrokes, mouse-movements, button use, browser actions)
> eye tracker
> video-recordings of screen-display
What are the results of the user tracing method?
- measure of information scent is able to generate good predictions to user-WWW interaction
- Most of the links chosen by the participants were ranked high by SNIF-ACT
(ACT predict which links people will click on a web page) - Information scent was shown to be able to predict when people will leave a site
-> information scent of the site was decreasing
How are lists declaratively represented?
- as chunks, as set of groups (groups of 3)
- each chunk is represented using slots/ values
What is logic?
- the study of reasoning with definite knowledge
- important for our understanding of general purpose intellignce
- main requirement = formal language
- types
> propositional logic
> first order logic
what is propositional logic?
- symbols (stand for propositions that can be true/ false)
- logical connectives (and, or, not, if…then)
- limitations
> not very expressive
> generalisation
