An Instructors Outline of Designing the User Interface

An Instructor’s Outline of Designing the User Interface 4 th Edition by Ben Shneiderman & Catherine Plaisant Slides developed by Roger J. Chapman Copyright © 2005, Pearson Education, Inc.

Chapter 11 Design Issues Copyright © 2005, Pearson Education, Inc.

Why 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 products Copyright © 2005, Pearson Education, Inc.

Copyright © 2005, Pearson Education, Inc.

Core cognitive aspects • Attention • Perception and recognition • Memory • Reading, speaking and listening • Problem-solving, planning, reasoning and decision-making, learning Copyright © 2005, Pearson Education, Inc.

Design implications for attention • Make information salient when it needs attending to • Use techniques that make things stand out like colour, ordering, spacing, underlining, sequencing and animation • Avoid cluttering the interface - follow the google. com example of crisp, simple design • Avoid using too much because the software allows it Copyright © 2005, Pearson Education, Inc.

An example of over-use of graphics Copyright © 2005, Pearson Education, Inc.

Which is easiest to read and why? What is the time? What is the time? Copyright © 2005, Pearson Education, Inc.

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 • We recognize things much better than being able to recall things – The rise of the GUI over command-based interfaces • Better at remembering images than words – The use of icons rather than names Copyright © 2005, Pearson Education, Inc.

The problem with the classic ‘ 7 2’ • George Miller’s theory of how much information people can remember • People’s immediate memory capacity is very limited • Many designers have been led to believe that this is useful finding for interaction design Copyright © 2005, Pearson Education, Inc.

Understanding how interfaces affect users • Expressive interfaces – how the ‘appearance’ of an interface can elicit positive responses • Negative aspects – how computers frustrate users • Anthropomorphism and interface agents – The pros and cons • Designing synthetic characters Copyright © 2005, Pearson Education, Inc.

Affective aspects • HCI has generally been about designing efficient and effective systems • Recently, move towards considering how to design interactive systems to make people respond in certain ways – e. g. to be happy, to be trusting, to learn, to be motivated Copyright © 2005, Pearson Education, Inc.

Expressive interfaces • Color, icons, sounds, graphical elements and animations are used to make the ‘look and feel’ of an interface appealing – Conveys an emotional state • In turn this can affect the usability of an interface – People are prepared to put up with certain aspects of an interface (e. g. slow download rate) if the end result is very appealing and aesthetic Copyright © 2005, Pearson Education, Inc.

Friendly interfaces • Microsoft pioneered friendly interfaces for technophobes - ‘At home with Bob’ software • 3 D metaphors based on familiar places (e. g. living rooms) • Agents in the guise of pets (e. g. bunny, dog) were included to talk to the user – Make users feel more at ease and comfortable Copyright © 2005, Pearson Education, Inc.

User-created expressiveness • Users have created emoticons - compensate for lack of expressiveness in text communication: Happy : ) Sad : < Sick : X Mad >: Very angry >: -( • Also use of icons and shorthand in text and instant messaging has emotional connotations, e. g. I 12 CU 2 NITE Copyright © 2005, Pearson Education, Inc.

User frustration • Many causes: – When an application doesn’t work properly or crashes – When a system doesn’t do what the user wants it to do – When a user’s expectations are not met – When a system does not provide sufficient information to enable the user to know what to do – When error messages pop up that are vague, obtuse or condemning – When the appearance of an interface is garish, noisy, gimmicky or patronizing Copyright © 2005, Pearson Education, Inc.

Expectations for Quality of Service • Introduction – 1960 s: mathematical computation association with computation time – World wide web: means graphics, & network congestion effect response time – Time is precious • Lengthy or unexpected system response time can produce: – Frustration – Annoyance – Eventual anger • Speedy and quickly done work can result in users: – – learning less reading with lower comprehension making more ill-considered decisions committing more data-entry errors Copyright © 2005, Pearson Education, Inc.

Models of response-time impacts • Response time – The number of seconds it takes from the moment users initiate an activity until the computer presents results on the display • User think time – The number of seconds the user thinks before entering the next action Copyright © 2005, Pearson Education, Inc.

Models of response-time impacts • Designers of response times and display rates in HCI must consider: – – – – complex interaction of technical feasibility cost task complexity user expectations speed of task performance error rates error handling procedures Copyright © 2005, Pearson Education, Inc.

Models of response-time impacts • Overall majority of users prefer rapid interactions – Lengthy response times (15 seconds) are detrimental to productivity – Rapid response times (1 second or less) are preferable, but can increase errors for complex tasks Copyright © 2005, Pearson Education, Inc.

Models of response-time impacts • Display Rate – Alphanumeric displays: The speed in characters per second at which characters appear for the user to read – World Wide Web Applications: Display rate may be limited by network transmission speed or server performance • Reading textual information from a screen is a challenging cognitive and perceptual task – Users relax when the screen fills instantly- beyond a speed where someone may feel compelled to keep up Copyright © 2005, Pearson Education, Inc.

Models of response-time impacts • Cognitive human performance would be useful for: – making predictions – designing systems – formulating management policies Copyright © 2005, Pearson Education, Inc.

Models of response-time impacts Limitations of short-term and working memory • Any cognitive model must emerge from an understanding of human problem-solving abilities • Magic number seven - plus or minus two – The average person can rapidly recognize seven chunks of information at a time – This information can be held for 15 to 30 seconds in short-term memory – Size of the chunks depends on the person' s familiarity with the material Copyright © 2005, Pearson Education, Inc.

Models of response-time impacts • Short-term memory and working memory are used in conjunction for processing information and problem solving – Short-term memory processes perceptual input – Working memory generates and implements solutions • People learn to cope with complex problems – develop higher-level concepts using several lower-level concepts brought together into a single chunk • Short term and working memory are highly volatile – Disruptions cause loss of memory – Delays require that memory be refreshed Copyright © 2005, Pearson Education, Inc.

Models of response-time impacts Source of errors • Solutions to problems must be recorded to memory or implemented – Chance of error increases when solutions are recorded • When using an interactive computer system users may formulate plans and have to wait for execution time of each step • Long (1976) found unskilled and skilled typists worked more slowly and made more errors with longer response times – For a given user and task, there is a preferred response time Copyright © 2005, Pearson Education, Inc.

Models of response-time impacts Conditions for optimum problem solving • Longer response time causes uneasiness in the user because the penalty for error increases • Shorter response time may cause the user to fail to comprehend the presented materials • Progress indicators shorten perceived elapsed time and heighten satisfaction: – graphical indicators – blinking messages – numeric seconds left for completion Copyright © 2005, Pearson Education, Inc.

Models of response-time impacts Conditions for optimum problem solving (cont. ) • Rapid task performance, low error rates, and high satisfaction can come from: – Users have adequate knowledge of the objects and actions necessary for the problem-solving task – The solution plan can be carries out without delays – Distractions are eliminated – User anxiety is low – There is feedback about progress toward solution – Errors can be avoided or handled easily Copyright © 2005, Pearson Education, Inc.

Models of response-time impacts Conditions for optimum problem solving (cont. ) • Other conjectures in choosing the optimum interaction speed – Novices may exhibit better performance with slower response time – Novices prefer to work at slower speeds – With little penalty for an error, users prefer to work more quickly – When the task is familiar and easily comprehended, users prefer more rapid action – If users have experienced rapid performance previously, they will expect in future situations Copyright © 2005, Pearson Education, Inc.

Expectations and attitudes Related design issues may clarify the question of acceptable response time – E. g. how long before hearing a dial-tone • Two-second limit (Miller, 1968) appropriate for many tasks • But users have adapted a working style and expectation based on responses within a fraction of a second • People can detect 8% changes in a 2 -4 second response time Response-time choke • A system is slowed down when the load is light and potential performance high • Makes the response time more uniform over time and across users, avoiding expectations that can’t always be met Copyright © 2005, Pearson Education, Inc.

Expectations and attitudes Response time across web sites varies • It effects user interest and quality assessment Three things influence response-time: • Previous experiences • The individual's tolerance for delays • Task complexity Copyright © 2005, Pearson Education, Inc.

User productivity • Repetitive tasks – Nature of the task has a strong influence on whether changes in response time alter user productivity – Shorter response time means users responds more quickly, but decisions may not be optimal – Goodman and Spence (1981) – reduced response time lead to more productivity – Teal and Rudnecky (1992) – slower response time lead to more accuracy Copyright © 2005, Pearson Education, Inc.

User productivity • Problem solving tasks – Users will adapt their work style to the response time – Users will change their work habits as the response time changes – Grossberg, Wiesen, and Yntema (1976) – the time to solution was invariant with respect to response time Copyright © 2005, Pearson Education, Inc.

User productivity • Summary – Users pick up the pace of the system to work more quickly with shorter response time – Higher throughput of work demands more attention must be paid to minimizing the cost of delay of error recovery Copyright © 2005, Pearson Education, Inc.

Variability • People are willing to pay substantial amounts of money to reduce the variability in their life e. g. insurance • Goodman and Spence (1981) – Subjects took more advantage of fast response time by making their subsequent commands immediately and balancing the time lost in waiting for slower responses • Modest variations in response time (plus or minus 50% of the mean) appear to be tolerable • It may be useful to slow down unexpected fast responses Copyright © 2005, Pearson Education, Inc.

Frustrating experiences • (Ceaparu et al. , 2004) 46% to 53% of users’ time was seen as being wasted • Recommendations include improving the quality of service and changes by the user • Poor quality of service is more difficult in emerging markets and developing nations • User training can help • E-mail a common application, but also a common source of frustration (i. e spam) • Viruses also a problem Copyright © 2005, Pearson Education, Inc.