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Presentation 3:

Cognitive Psychology

& usable methods

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Outline

• Recap from last time– The History of HCI – and why it is important– “The Psychology of HCI”

• Delving further into Cognitive HCI• Methods we may employ• Performing a CW

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The History of HCI

• And why it is important – recap from last time– Why is it important to know the History?– Suggestions?

• Do NOT repeat the mistakes of others– Example: WAP – 1994 all over again?

• Rather:– Learn from those who went before you– Use their guidelines and methods (& theories)– And be able to understand what they are referring to!

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The Psychology of HCI

• It is not easy to control all aspects of your product development– You may be dependent on others to provide the technical settings

within which you must work• Hardware: processing power available, battery, display quality

• Software: low level programming (hard to make Windows systems in assembler or C), few available widgets (J2ME) or even no GUI at all!

– What you ARE able to do, is optimizing the resources you DO have, for the task ahead

– This includes anticipating what the user might want• Guessing (or is this a clever strategy?)

• Qualified assumptions based on heuristics (Aha History again!)

• Involving users in the design, and testing it (more of this later!)

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The Psychology of HCI

• Two main theoretic frameworks– Cognitive Sciences– Social Computing

• Both with user involvement!– But with different backgrounds– We will not spend too much time on discussing this– Only note, that the Cognitive School is more “hard

science” and “lab oriented” than is Social Computing

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Cognitive HCI

First generation: cognitive sciences (RECAP)– Cognitive psychology: the study of how people perceive, learn,

and remember (USA 1950’s)– Cognition: the act or process of knowing (DK: erkendelse/viden)– “The Psychology of HCI” until late 1980’s – Cognitive HCI– the human mind as a series of information processors – almost like

a computer, ready to measure against the computer, practical!• 3 parts – Input system, output system, information processor system• The body (eyes, muscles etc) is only hardware

– Input/output – stimulus/response – ultimatly: the PUM– hard science and practical concerns – engineering HCI

• Task analysis, Approximation, Calculation, models: KLA, GOMS

– Lab testing and “measuring” usability (Fittz law – Joystick/Mouse)– WE CAN MAKE MODELS OF EVERYTHING AND CALCULATE

USABILITY! GREAT!

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Cognitive sciences

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Cognitive characteristics

• The human “central information processing”– Here Cognition takes place

• Components of cognition– Short-term(working) vs Long-term memory

• Most GUI’S (& SUI’s) are memory intensive• Need to support the user get through the task (focus problems)• User can only comprehend 7+2 elements in short term memory

– Associative thinking • Using Icons to connect

– The Importance of meaning (humans remember things with …)• DOS, SOAP, CORBA harder than “File System” – use Metaphors

– Many other factors, which we will not delve into here• Read more in Shneiderman (Designing the User Interface)• Normans “The Design of Everyday things”• Nielsen's “Usability Engineering”

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Methods

• Cognition Psychology makes assumptions on user behavior – and believes in it– We can isolate users in the LAB and make testing that

is hard science (quantitative empirical data)• Method: Think out loud (Tognazzini – User testing on the

cheap)

– We can “predict” usability – task performance time (eg calculating number of necessary key strokes or mouse clicks - KLA) – by knowing things about the user

– We can try to “predict” usability problems, by simulating the user – done by designer & analyst

• Here the Cognitive Walkthrough is a qualitative method)

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Evaluation without users

• Quantitative Methods– GOMS/keystroke analysis (low level)– Back-of-the-envelope action analysis (well …)

• Qualitative Methods– Expert evaluation (high level)– Cognitive walkthrough (high level)– Heuristic evaluation (high level)– Think out loud (medium to high level)

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With or without users

• Users are the gold standard– They cannot be simulated perfectly

• Users are expensive and inconsistent– Usability studies require several users– Some users provide great information, others little– Nearly always qualitative studies

• Too expensive to make quantitative

• Best choice do both– Start out without – later with

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GOMS Analysis

• Goals– Change a word in a text document

• Operators– Click mouse, look at a menubar, remember a name

• Methods– Move mouse to point at word, then double-click

• Selection Rules (to decide which course of action to take) Use Cut menu, Delete key, etc.

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GOMS/Keystroke Analysis

• Formal action analysis– Accurately predict task completion time for skilled users

• Break task into tiny steps– Keystroke, mouse movement, refocus gaze– Retrieve item from long-term memory

• Look up average step times– Tables from large experiments

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GOMS/Keystroke Analysis

• Primary utility: repetitive tasks– e.g., telephone operators, SMS users (T9)– Benefit: can be very accurate (within 20%)– May identify bottlenecks

• Difficulties– Challenging to decompose accurately– Long/laborious process– Not useful with non-expert users

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GOMS Timing

• K = 0.2 sec– Tap a key on the keyboard

• P = 1.1 sec– Point to a position on a display

• H = 0.4 sec– Homing, moving from keyboard to mouse or back

• M = 1.35 sec– Mentally preparing

• R = ???– Responding

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Back-of-the-EnvelopeAction Analysis

• Coarse-grain– List basic actions (e.g., ‘select menu item’)– Each action can be 2-3 seconds (or less)– What must be learned/remembered?– What can be done easily?– Documentation/training?

• Goal is to find major problems

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Action Analysis example

• Windows File Open Dialog– Especially the NT & pre-2000– Takes additional seconds each time it is used– Does not remember sort order– Cannot be resized

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Semi-quantitative action analysis

• Windows File Open dialog F: 1.25 sec

O: 1.25

Move to folder: 1.25

D-click folder: 0.25

Sum = 4.0 sec

4 sec x 5x/day x 1 million users = 5,555 hrs/yr

$416,625.00

($75/hr)

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Windows File Open (Continued)

To details button: 1.25 sec 0.5 sec

To column separator: 1.25 sec 1.0 sec

To 2nd col separator: 1.25 1.0

To Mod col head: 1.25 1.0

Sum = 5.0 sec 3.5 sec

3.5 x 5x/day x 1 million users = 4,861 hrs/yr

$364,575.00

($75/hr)

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Is it worth a redesign?

• This is the one that shows up in MS Powerpoint in Windows 2000™

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Expert evaluation

• Usability specialists are very valuable– Double-specialists are even better

• An inexpensive way to get a lot of feedback• Be sure the expert is qualified in your area

Confusing Dialog?

Do you really want to Cancel your shortsell order on the leveraged options?

Yes Forget It

“This should be ‘Cancel’… that’s what the guidelines say”

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Walkthrough Analysis

• Economical interface evaluation– Low-fidelity prototype– Development team

• Users optional

• Effective, if– Goal is improvement, not defense– Some team members skilled– Proper motivation

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Cognitive Walkthrough

• Goals– to critique the designers assumptions about the design

• Imagine user’s experience• Evaluate choice-points in the interface• Detect e.g. confusing labels or options• Detect likely user navigation errors

• Start with a complete scenario– Never try to “wing it” on a walkthrough

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Tell a Believable Story

• How does the user accomplish the task• Action-by-action

– Tasks should be important– Tasks should be realistic

• Based on user knowledge and system interface

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Best Approach

• Work as a group– Don’t partition the task

• Be highly skeptical– Remember, the goal is to improve the UI

• Every gap is an interface problem

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Who Should Do the Walkthrough

• Designers, as an early check• Team of designers & users

– Remember: goal is to find problems– Avoid making it a show

• Skilled UI people may be valuable team members

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How Far Along

• Basic requirements– Description or prototype of interface– Know who users are (and their experience)– Task description– List of actions to complete the task (scenario)

• Viable once the scenario and interface sketch are completed

• But can be done anytime …

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Outline of CW

• Preparation– Define assumed user background– Choose sample task– Specifiy correct action sequence(s) for task– Determine interface states along the sequence(s)

• Analysis– For each correct action

• Construct a success story that explains why a user would choose that action OR

• Use a failure story to indicate why a user would not choose that action– Record problems, reasons & assumptions– Consider and record design alternatives

• Follow-up– Modify the interface design to eliminate problems -> redesign!

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How to Proceed

• For each action in the sequence– Tell the story of why the user will do it– Ask critical questions

• Will the user be trying to achieve the right effect?• Will the user notice that the correct action is available?• Will the user select a different control instead?• Will the user associate the correct action with the

desired effect?• Will the user understand the feedback – and that

progress has been made?

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The Questions

• Will the user be trying to achieve the right effect?• Will the user notice that the correct action is

available?• Will the user select a different control instead?• Will the user associate the correct action with

the desired effect?• Will the user understand the feedback – and that

progress has been made?

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Walkthroughs are not Perfect

• They won’t find every problem• A useful tool in conjunction with others• Conclusions from Lewis & Wharton (taken from overview of

different related studies)– CW finds about 40% (or more) og the problems later revealed by user

testing– CW takes substantially less effort than user testing– Considering problems found per unit effort, CW may not be much

more cost effective than user testing– Heuristic Evaluation finds more problems than the CW and takes less

effort– CW can be tedious and too much concerned with low-level details– CW does not provide a high-level perspective on the interface– CW’s performed by groups of analysts work better than those done by

individuals• After the exercises – you may form your own opinion

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Exercise: Cognitive Walkthrough Analysis

• In non-project groups of 3-5• Scenario developed jointly

– Coffee Vending machine (group 1 starts)

• Perform walkthrough– identify problems

– estimate error probabilities (25% intervals)

• Remember who your users are!• AND WRITE EVERYTHING DOWN

– We will be meeting in 1 hour again