User-Centered Design and DevelopmentCopyright Notice484-W09 QuarterChapter 3Chapter OverviewMotivationObjectivesUnderstanding usersOverviewWhy do we need to understand users?1. Bringing cognitive psychology knowledge to HCICore cognitive aspectsAttentionDesign implications for attentionAn example of over-use of graphicsPerception and RecognitionWhich is easiest to read and why?MemoryThe Classic ‘72’What some designers get up to…Why?Application of Memory ResearchFile ManagementMental modelsHistory of Mental ModelsEveryday Reasoning and Mental ModelsHeating up a room or oven that is thermostat-controlledSlide 28Exercise: ATMsHow did you fare?External cognitionExternalizing to reduce memory loadActivity: Examples of External Cognition SupportComputational OffloadingAnnotation and Cognitive TracingDesign ImplicationsInforming design based on our understanding of usersMental Models and System DesignThe design principle of transparencyKey pointsUser-Centered Design and Development Instructor: Franz J. KurfessComputer Science Dept.Cal Poly San Luis ObispoFJK 2005Copyright Notice•These slides are a revised version of the originals provided with the book “Interaction Design” by Jennifer Preece, Yvonne Rogers, and Helen Sharp, Wiley, 2002.•I added some material, made some minor modifications, and created a custom show to select a subset.–Slides added or modified by me are marked with my initials (FJK), unless I forgot it …FJK 2005484-W09 Quarter•The slides I use in class are in the Custom Show “484-W09”. It is a subset of the whole collection in this file.•Since the time for lectures in week 3 is very short due to the UCD tools presentations, I’m using only a very small subset from this chapter.Chapter 3Understanding UsersChapter Overview•Cognition•Physical world vs. digital world•Conceptual frameworks for cognition–mental models–information processing –external cognitionFJK 2005Motivation•Well-designed user interfaces and user interactions require an understanding of the way users think and feel with respect to the product•Cognitive science provides some models and other hints that can be used for interaction design.•Different types of cognitive approaches may be appropriate for different users, situations, or tasks.FJK 2005FJK 2005Objectives•Become familiar with some concepts from cognitive science that help with the design of user interaction.•Identify the appropriate cognitive model for a particular task, user, or situation.•Know when to transfer knowledge about interaction in the physical world to the digital world.•Utilize methods and principles from cognitive science and related fields to improve interaction design.Understanding usersOverview•What is cognition?•What are users good and bad at?•Mental models•External cognition•Using this understanding to inform system designWhy do we need to understand users?•Interacting with technology is cognitive•We need to take into account cognitive processes involved and cognitive limitations of users•We can provide knowledge about what users can and cannot be expected to do•Identify and explain the nature and causes of problems users encounter•Supply theories, modelling tools, guidance and methods that can lead to the design of better interactive products1. Bringing cognitive psychology knowledge to HCIWhat goes on in the mind?perceiving..thinking..remembering..learning..understanding otherstalking with othersmanipulating othersplanning a mealimagining a trippaintingwritingcomposingmaking decisionssolving problemsdaydreaming...Core cognitive aspects •Attention•Perception and recognition•Memory•Reading, speaking and listening•Problem-solving, planning, reasoning and decision-making, learning•Here we focus on attention, perception & recognition, & memoryAttention •Selecting things to concentrate on –percepts contain many potential items of interest–at a given point in time•Focussed and divided attention –enables us to be selective –competing stimuli–limits our ability to keep track of all events•Information provided at the interface –structured to capture the attention of users•use perceptual boundaries (windows), color, reverse video, sound and flashing lights •Selecting things to concentrate on –percepts contain many potential items of interest–at a given point in time•Focussed and divided attention –enables us to be selective –competing stimuli–limits our ability to keep track of all events•Information provided at the interface –structured to capture the attention of users•use perceptual boundaries (windows), color, reverse video, sound and flashing lightsDesign implications for attention•Make information salient –when it needs attending to•Use techniques that make things stand out –color, ordering, spacing, underlining, sequencing and animation•Avoid cluttering the interface–crisp, simple design•e.g. google.com•Avoid using too much –just because the software allows itAn example of over-use of graphicsOur Situationu State the bad newsu Be clear, don’t try to obscure thesituationPerception and Recognition•Information acquisition–collection percepts about the world –transformation into experiences•Design representations that are readily perceivable–text should be legible–icons should be easy to distinguish and readWhich is easiest to read and why?What is the time?What is the time?What is the time?What is the time?What is the time?What is the time?Memory•Involves encoding and recalling knowledge–and acting appropriately•We don’t remember everything–involves filtering and processing•Context is important in affecting our memory•Recognition over recall–We recognize familiar things much better than being able to recall these things–GUI vs. command-based interfaces•Better at remembering images than words–use of icons rather than names–interpretation of icons can be problematicThe Classic ‘72’•George Miller’s theory of how much information people can remember–72 “chunks” of information•People’s immediate memory capacity is very limited–short-term memory–not under conscious control•Implications for interaction design–relevant for some aspects, but not others–prone to oversimplificationWhat some designers get up to…•Present only 7 options on a menu•Display only 7 icons on a tool bar•Have no more than 7 bullets in a list•Place