UG4: HCI Lecture 4 1 · UG4: HCI Lecture 4 1 1 Lecture 4: The User IV: Are People Really ‘in the Know’? Jon Oberlander UG4: HCI Lecture 4 2 Introduction Where does the knowledge

UG4: HCI Lecture 4 1

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Lecture 4:The User IV: Are People Really ‘in the Know’?

Jon Oberlander


Introduction

Where does the knowledge necessary for acting in the worldcome from?

Is this knowledge ‘in the head’? If so, how (in a general sense) might this knowledge be

organised? If this knowledge is not all in the head, where is it?

– How do users get by if they are not experts in the domain?


Mental Models: ‘Knowledge in the Head’?

Different kinds of knowledge may be distinguished:– Declarative, how-it-works, device knowledge– Procedural, how-to-do-it knowledge– Episodic knowledge

Declarative knowledge – a ‘mental model’ – provides means forreasoning about:– Effects of actions– Tuning procedural knowledge


Primary Knowledge

Domain – goals relevant to application domain and the tasksrequired to accomplish them

Semantics – conceptual knowledge of ‘entities’ and ‘operations’ Syntax – dialogue rules: input/output ‘language’ Lexical – physical actions We might think of these different knowledges as an associatively

linked, layered structure



Example: Document Formatting

Domain – document presentation; aesthetics; format Semantics – words, sentences, paragraphs, pages, typefaces;

justification, indexing; Syntax –form of command specification; sequencing rules Lexical – key, button presses; mouse movements Domain and semantic knowledge may vary according to

document type Syntactic, lexical (and often semantic) knowledge may vary

according to the system– Compare LaTex with Word


Domainknowledge

Knowledgeof systemoperationsand entities

Knowledgeof dialogue

rules

Lexicalknowledge

Knowledge ofnatural language

How-it-worksknowledge

Knowledgeof othersystems

What ‘Knowledge in the Head’ Looks Like


Mental Models and Interaction

If we have complete knowledge of an interface then perhapsinteraction too is ‘in the head’

But, observations suggest that knowledge in the head is:– Seldom either complete or accurate– Unstable, changing and decaying over time– Lacks firm boundaries– Not strictly ‘scientific’ or even ‘rational’

• E.g., the problem of false causality


Secondary Knowledge

Knowledge of natural language Knowledge of using other systems/technologies

– Email• Telephone?• Post?• Elements of both?• Neither?

Secondary knowledge may encourage analogical mapping– Metaphor in interface design

Otherwise, it’s time for situated action– Affordances in interface design



Metaphor

Linguistically: “X is like Y” Speech and thought are littered with metaphor

– Computer ‘memory’– ‘Windows’– ‘A text editor is like a typewriter’– ‘A computer is like a desktop’


What Makes a Good Metaphor?

In the source and target domains, there should be:– Entity resemblances– Relational resemblances

People should be familiar with the source domain:– Significant entity/relational features should be ‘obvious’


Metaphor Example

Solar system and atomic structure– Sun and planets -> nucleus and electrons– Planets revolve around sun -> electrons revolve around the nucleus– Sun much heavier than planets -> nucleus much heavier than

electrons

On delving more deeply, the metaphor is left behind andbecomes redundant


Metaphor Scope

A good metaphor will have a wide scope The desk-top metaphor:

Domain: “Can I change the arrangement of my documents?”Semantic: “What is the wastebasket for?”Syntax: “What is the procedure for throwing a document away?”Lexical: “How do I perform the action of throwing a document

away?”; “How do I open a folder?”



Learning and Metaphor

Exploiting existing knowledge for learning Users prefer ‘learning by doing’ or (‘learning by observing’) Metaphor provides clues for abductive reasoning ‘Text editors are like typewriters’:

– Alphanumeric keys– Space, backspace, carriage return

Mismatches prompt investigation and learning– Correspondences, non-correspondence and indeterminate

correspondence

Metaphor encourages systematic investigation


Affordances: ‘Knowledge in the World’?

Affordances: perceived and actual properties of artefacts– Presenting the ‘potential for action’

Affordances illustrate the importance of:– Visibility– Feedback– Clues for action, supporting improvisation

“If a door handle needs a sign, then its design is faulty”D. Norman, The Psychology of Everyday Things


Norman on doors


Norman on doors



Norman on doors


Norman on doors


Norman on doors


Norman on doors



Guidelines for Design

Where users are domain experts, focus on users’ knowledge ofthe application domain– Reduce learning

Where users are not domain experts, base the system image ona suitable metaphor– But don’t follow slavishly

Always make the system image explicit– Make system behaviour clear and accountable

Encourage learning by exploration– Provide safeguards; make errors easy to reverse

Reduce memorisation and support improvisation by exploitingaffordances– Put knowledge into the interface, not just interface mechanisms but

how to use them


Further Reading and Suggested Exercise

Dix et al., 2nd ed: chapter 1, p. 36-47;3rd ed: chapter 1, p. 39-50.

Newman and Lamming, chapter 13, p. 325-43.

Consider your knowledge of the www, identifying the differentkinds you routinely employ when using it.

Documents

UG4: HCI Lecture 4 1 · UG4: HCI Lecture 4 1 1 Lecture 4: The User IV: Are People Really ‘in the Know’? Jon Oberlander UG4: HCI Lecture 4 2 Introduction Where does the knowledge