AVI/Psych 358/IE 340: Human Factors

Interfaces and InteractionSeptember 22, 2008

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Designing Interfaces

• Human-Computer Interaction (HCI) has moved beyond designing interfaces for desktop machines

• Concerned with extending and supporting all aspects of human activities through design and evaluation (social, emotional, physical etc.)

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Understanding the problem space

– What do you want to create?– What are your assumptions?– What are your claims?– Will it achieve what you hope it will? If so,

how?

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An example

• What do you think were the main assumptions made by developers of online photo sharing and management applications, like Flickr?

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Assumptions

• Able to capitalize on the hugely successful phenomenon of blogging

• Just as people like to blog so will they want to share with the rest of the world their photo collections and get comments back

• People like to share their photos with the rest of the world

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From problem space to design space• Having a good understanding of the problem

space can help inform the design space• But before deciding upon these it is important to

develop a conceptual model

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What is a conceptual model?

• “a high-level description of how a system is organized and operates.”– What functionality to provide– What would the website do (overall)– Who would use it?

• E.g.: a university website, or Orbitz, youtube etc.

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Why do we need it?

• NOT a description of the user interface• But a structure outlining the concepts and the

relationships between them• Helps the design team

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Ponzo’s illusion

• Ambiguity– Human mind perceives

object’s size based on the background

– Interpret based on a linear perspective

– Moon illusion (bigger at the horizon than at the top)

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A classic conceptual model: the spreadsheet

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Why was it so good? (1/2)

• It was simple, clear, and obvious to the users how to use the application and what it could do

• “It is just a tool to allow others to work out their ideas and reduce the tedium of repeating the same calculations.”

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Why was it so good? (2/2)

• Capitalized on user’s familiarity with ledger sheets

• Got the computer to perform a range of different calculations and recalculations in response to user input

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Interface metaphors

• Designed to be similar to a physical entity but also has own properties– e.g. desktop metaphor, search engine, trash

• Exploit user’s familiar knowledge, helping them to understand ‘the unfamiliar’

• People find it easier to learn and talk about what they are doing at the computer interface in terms familiar to them

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Problems with interface metaphors (Nelson, 1990)• Breaks the rules• Too constraining• Limits understanding around metaphor• Conflicts with design principles• Limits designers’ imagination

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Interaction types

• Instructing• Conversing• Manipulating• Exploring

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Instructing

• Where users instruct a system by telling it what to do

• A main benefit of instructing is to support quick and efficient interaction

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Conversing

• Like having a conversation with another human

• Ranges from simple voice recognition menu-driven systems to more complex ‘natural language’ dialogues

• Examples include search engines, advice-giving systems, and help systems

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Ask Jeeves for Kids!

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Manipulating

• Exploit’s users’ knowledge of how they move and manipulate in the physical world

• Virtual objects can be manipulated by moving, selecting, opening, and closing them

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Direct manipulation

• Shneiderman (1983) coined the term Direct Manipulation• Proposes that digital objects be designed so they can be

interacted with analogous to how physical objects are manipulated

• Assumes that direct manipulation interfaces enable users to feel that they are directly controlling the digital objects

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Core principles of DM

• Physical actions and button pressing instead of issuing commands with complex syntax

• Rapid reversible actions with immediate feedback on object of interest

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Discussion

• Give some examples of DM for Windows (e.g., desktop, Microsoft Word)

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Why are DM interfaces so enjoyable? (1/2)

• Novices can learn the basic functionality quickly• Experienced users can work extremely rapidly to carry

out a wide range of tasks, even defining new functions • Intermittent users can retain operational concepts over

time

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Why are DM interfaces so enjoyable? (2/2)

• Error messages rarely needed• Users can immediately see if their actions are furthering

their goals and if not do something else• Users experience less anxiety• Users gain confidence and mastery and feel in control

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What are the disadvantages of DM?• Some people take the metaphor of direct manipulation

too literally• Some tasks are better achieved through delegating

rather than manipulation, e.g., spell checking• Moving a mouse around the screen can be slower than

pressing function keys to do same actions (e.g., shortcuts)

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Video game controllers

• Compare the direct manipulation between the Wii remote and other traditional video game controllers (e.g., Xbox, PlayStation)

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Exploring

• Involves users moving through virtual or physical environments

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A virtual world

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A CAVE

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Summary points

• Need to have a good understanding of the problem space– specifying what it is you are doing, why, and how it will

support users in the way intended

• A conceptual model is a high-level description of a product (not the interface)– what users can do with it and the concepts they need to

understand how to interact with it

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Summary points

• Decisions about conceptual design should be made before commencing any physical design

• Interface metaphors are commonly used as part of a conceptual model

• Interaction types (e.g., conversing, instructing) provide a way of thinking about how best to support the activities users will be doing when using a product or service

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Summary points

• Different types of interactions– Instructing– Conversing– Manipulating– Exploring