1. Knowledge, Mental Models and HCI

2. Introduction 4 If we want to –predict learning time –identify “typical” errors –relative ease of performance of tasks 4 Then we need ways of discovering –what users know about the system –how users reason about the system

3. Types of Knowledge Representation 4 Analogical Representation –picture-like representations 4 Propositional Representations –abstract statements that make assertions 4 Distributed Representations –networks of nodes where knowledge is implicit in the connections between them Symbolic Sub-symbolic

4. Schools of Thought 4 Imagists vs. Propositionalists –imagists believe that images play a distinctive role in cognitive processes –propositionalists believe that they are a by- product that plays no role, instead language-like propositions are key

5. Imagists v Propositionalists Which figure cannot be constructed from the pattern?

6. Connectionists 4 It seems likely that people use both images and propositions in thinking 4 Connectionists argue that the two are complementary and can exist together at higher levels of representation 4 But they are emergent properties of neural networks of nodes at a lower (sub- symbolic) level

7. Connectionist Networks Name Nationality Sex Favourite Football Team Course Favourite drink Alan ChelseaISYS1154 Guinness Male Irish

8. Knowledge Organisation 4 Knowledge is clearly highly organised 4 But as semantic networks? –nodes are objects (farmers, cows, sheep) and the links the relationship between them (farmers own cows etc.) 4 Or as schemata ? –repeatable patterns of experience (stereotypical scripts)

9. Mental Models 4 Developed to account for more dynamic aspects of cognitive activity 4 “...the model people have of themselves, others, the environment, and the things with which they interact. People form mental models through experience, training and instruction”

10. Structural vs. Functional models 4 Structural models are used to describe internal mechanics of a device in terms of its components (white box) 4 Functional models are used to describe how a device should be used (black box)

11. Key Points 4 3 types of mental representations: analogical, propositional and distributed 4 General knowledge is stored as schemata which, when activated, can be used to construct mental models 4 Mental models enable people to generate descriptions and explanations about systems, and make predictions 4 Structural models describe how systems work, functional models how they are used 4 Most people’s understanding of systems, devices is Functional 4 Conceptualizing users’ knowledge in terms of mental models can help designers to develop appropriate user interfaces