Session 2: External Cognition (17 may)

Paper: Mike Scaife and Yvonne Rogers (1996) External cognition: how do graphical representations work?
Int. J. Human -Computer Studies 45: 185-213.

Some notes:
1. Internal and external visual representations
• What is the nature of the relationship/ interaction between these? External cognition approach
– External reps a central functional role in relation to internal cognitive mechanisms (not an equivalence structure)
– Focus on the cognitive processing
– The properties of internal and external structures and cognitive benefits of reps
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2. Three central characteristics for analytical framework
• Computational offloading
• Re-representation
• Graphical constraining (limiting abstraction, restricting interpretation)

3. Resemblance fallacy
• How subjects identify key features and constraints?
• External and internal reps are simply assumed to have same characteristics!
• More a matter of learning to read the external?

4. Processing and the internal/external
• How the I and the E act in concert?
• How understanding is integrated with existing knowledge, interpreted, and re-represented externally?
• Complex, cyclical, interacting processes over time

5. Aspects of design - bridging
• Visual organization structures
• Type of notation (symbols and icons) used
• Canonical forms of representation (e.g. diagrams)
• Recognition of reading rules - cues appropriate inferences
• Ability to use representations
• Degree of abstraction
• Cognitive traces - annotations
• Levels of activity- how people interact with External representation