Usability - cognitive Factors - Baobab Health Trust, March 2014

Baobab Health, March 2014Harry Hochheiser, [email protected]

Introduction to Human-Computer Interaction – Cognitive Issues

Attribution-ShareAlike CC BY-SA

Harry Hochheiser University of Pittsburgh Department of Biomedical Informatics [email protected] !+1 410 648 9300

mailto:[email protected]


What is usability?

" What does it mean to be usable? " Which factors influence usability? " How can we make an interface usable? " Is interface design an art or a science?

!" Goal – develop some intuitions



What does it mean to be “usable”?

" Find something usable " Software, hardware, etc.

" Why is it usable? What do you mean when you say that? " Something unusable?

" What doesn't work? What's hard?



Usability Successes



Usability Failures



A Usability FailureThe light switch in my office…



A Usability FailureControl to turn off light sensor



A Usability Failure

Controls??

How might we improve upon this?



Dimensions of Usability

"Efficiency "Learnability "Memorability "Error Handling/Prevention "Satisfaction



Efficiency

" Can the system be used to complete the specified task? " How much time does it take to complete a task? " How many operations? " How much movement?



Learnability

" How quickly can a novice learn to use tool? " What help/assistance is given? " Consistency with similar system and/or convention?



Memorability

" Retention of proficiency over time? " Reminders and cues " Recognition vs. Recall " Minimizing cognitive load



Error Prevention/Handling

"What is the error rate? "Slips vs. mistakes "Preventing errors "Responding to errors



Satisfaction

" Do users feel that the tool was usable? " Do they want to use it more? " Is it aesthetically appealing?

" Don Norman: “Attractive things work better”



Tradeoffs/challenges

" Efficiency vs. Learnability " Expert interfaces

" Learnability vs. power/expressive control? " Power tools may be hard to learn

" Satisfaction vs. learnability " Hidden interactions on tablets

" Efficiency vs. Errors?



Human Abilities

Motor Abilities: How we can manipulate our world

Perception: What we take in from surroundings

Cognition: What we know

!

Capabilities influence theories, models, guidelines, etc.

leading to interfaces based on realistic understanding of what people can do and how they can work.

not how we think they should work.



Motor abilities• How quickly can we move around?

• Cost of various actions

• mouse vs. keyboard?

• cut down on number of steps required?

Fitts's law: time between two targets is proportional to distance + inverse of size of targets:

a – start time, b - speed of device, d- distance, w – target widths



BAOBAB JAMA video..

BAOBAB Screen shots.



Perception

Visual

Tactile

Auditory

Taste/Smell

rarely used in HCI



Visual PerceptionGood use of Contrast/Color help

except when they don't – color blindness

Which 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?



show baobab web site.



Pre-attentive Processing

• Limited set of visual properties are processed pre-attentivel without need for focusing attention • < 200 - 250ms qualifies as pre-attentive !

• Important for design: • what can be perceived immediately: things pop out • what properties are good discriminators

• Color, shape • what can mislead viewers !

• Combinations may not be pre-attentive



Find the red circle



Not Pre-attentive: conjunction of shape and color



• Pattern perception driven by

• proximity

• similarity

• smooth/good continuation

Perceptual Grouping - Gestalt



Grouping Rosenholtz, et al. 2009



Cognitive concerns

Attention

Memory

long-term

short-term

Language: reading, speaking, listening

Problem solving: planning, reasoning & decision-making

Learning



Attention We don't see -or “attend to” most of the world around us

attention -filtering out the noise

without attention, we'd couldn't function

how do we capture attention

“retinal attributes” intensity, marking, size, fonts, color..

change

• movement

• lights

• sound

• etc..

Cost of capturing attention: distraction



Question: When to claim attention?

Want to notify users of problems

Each claim on attention has a cost

context-shift takes time, loses focus

When should an interface interrupt the user?



Change Blindness http://www.youtube.com/watch?v=Ahg6qcgoay4



Short-term Memory

temporary recall

small - 7 +/-2 “chunks” • George Miller – remembering strings of numbers

rapid access, rapid decay

repeat to send to long-term

sometimes used in interaction design.

not necessarily appropriate.

• interfaces are about recognition

• STM is about recall



Long-term memory

Huge capacity

Slow access, decay

episodic: events and experiences

semantic: structured records of facts, concepts, skills.



Examples of ways that interfaces can work with memory constraints?

• Don't overtax short-term

• excel copying

• Help build long-term

• consistency

• (don’t force people to remember what’s been entered -)

• vb screenshot.



Conceptual models" Mental constructions that describe how something works

" or how you think it works

Good models help with predictability

key concept in HCI

To build good conceptual model

must understand the way users work and approach problems

otherwise, you get interfaces that reflect models from the designer, organization, etc., that don't reflect how users work.

Deep vs. shallow

deep – understanding of mechanisms - “white box”

shallow – how to use something - “black box”



Whose conceptual model? Don Norman, Design of Everyday Things



Norman's Refrigerator Thermostat Don Norman, Design of Everyday Things



Norman's refrigerator thermostatMental Models

It's been > 15 years since I first read this book, and I'm still confused by this model.

.. and my fridge is still not correctly adjusted.



Examples of mental model mismatches?



Language: reading, speaking, listening

• We're good at these things

• but, they require attention

• May distract from other tasks

• don't like to read manuals

• try listening to the news while you work on computer

• Speech recognition: thinking about your voice controls may interfere with language tasks (i.e, writing)



Problem solving: planning, reasoning & decision-making

• When solving the problem of how to accomplish a task with the computer..

• System should help figure out next tasks

• logical design – visibility and mapping

• When trying to use the computer to solve a problem

• System should get out of the way

• Not distract from focus on problem

• interfaces that disappear

• No one wants to just “use the computer” - they want to accomplish goals



The Psychopathology of Everyday ThingsDon Norman – Design of Everyday Things, Ch. 1

Favorite quote: “if a door handle needs a sign, then its design is probably faulty”

“When simple things need pictures, labels, or instructions, the design has failed”

Thinking about how design relates to human psychology

ideally, design should be consistent with how we think

Learn from failures

Principles all applicable to computer interfaces



Norman's Seven Stages of Actions

Form goal Form intention Specify action execute action perceive state interpret state evaluate outcome !!Cycles evaluation – mismatch between system output and user expectations



Gulfs of Execution and Evaluation

User Goals System Capabilities

Gulf of Execution - interface design

Intentions Action Specification

Interface Mechanism

Gulf of Evaluation - information design

Interface Display

InterpretationEvaluation



• Goal: Enter a new prescription

• Initial intention: How do I decide where to start?

• selecting a medication…

• Action Specification: Once I know first step, what do I do?

• Interface Mechanism: which buttons do I press, in which order?

Gulf of Execution



• After execution

• Interface display: What happened/changed in response to my action?

• Interpretation: What does it mean?

• Evaluation

• did the right thing happen?

• am I closer to my larger goal?

• do I need to change my goal or my choice of tactics?

!

Gulf of Evaluation



Bridging Gulfs

Execution clarity of action

Transparent interfaces with affordances

Wizards

Help/Tutorials

Evaluation Feedback

Explanation

Error Messages

Undo



Affordances

“actionable properties between

the world and an actor (a person or animal).” (Gibson, quoted by Nielsen http://www.jnd.org/dn.mss/affordances_and.html)

!“Perceived affordance” - design that communicates possibility of an action to the user.

!

What makes an affordance? Examples?


http://www.jnd.org/dn.mss/affordances_and.html


Models

Response time - how long it takes from initiation to display of results

Think time – time before starting next action

As response time decreases, approach simpler model

Interface can help reduce planning time?

How to measure think time?



• Predictive Models of task completion times

• Motion

• Button press

• Think, etc.

• CogTool: www.cogtool.com

Keystroke-Level Models & Goals, Operators, Methods, Selection Rules


http://www.cogtool.com


Cogtool and ANC



Cognitive Load, Errors, and Response Time

More effort spent planning and waiting increases cognitive load and short-term memory - more errors

But, errors are more expensive

vicious cycle

Interruptions can be expensive

derail thinking/flow



Mappings

Correspondence between what you want to do

what appears to be possible

You want to go forwards/backwards, but controls are only up and down

visibility indicates mapping between intended actions and operations.

Light switches in order of where the lights are?

Good mappings reduce cognitive overload

leverage previous knowledge



Mapping Successes and/or Failures?

Refrigerator controls -

2 controls implies 2 systems to regulate

!

Others?



Visibility• “correct parts must be visible, and they must convey the

correct message”.

• “natural signals”

• What's natural in a computer interface? • what's intuitive?

• What does visibility look like?

• Is strict visibility crucial?

• Weaker notion: parts that aren't immediately visible should be findable in appropriate places?

• “Whenever the number of possible actions exceeds the number of controls, there is apt to be difficulty.”



• Interfaces are languages

Levels of Visibility Lexical-Syntactic-Semantic-Conceptual Foley & van Dam, as interpreted by Myers

(http://www.cs.cmu.edu/~bam/uicourse/830spring13/830-09-softorg.pptx)

Letters/Words Sentences Paragraphs Ideas

Lexical Syntactic Semantic Conceptual

Keys, Buttons, Sequences Tasks Domain Concepts


http://www.cs.cmu.edu/~bam/uicourse/830spring13/830-09-softorg.pptx


• Spelling and composition of “tokens”

• “add” vs. “append” vs “^a” vs

• Location of controls

• “Key-stroke”

• Make items visible

• Distinguish between items that can and cannot be acted upon

Lexical Visibility Myers http://www.cs.cmu.edu/~bam/uicourse/830spring13/830-09-softorg.pptx




• Ordering of inputs

• Legal a tokens must sensible order in?

Syntactic Visibility

• Tokens must be used in a legal, sensible order.

• Visual cues can improve visibility

• Gray out inactive/inappropriate items

• Grouping and spacing



• System functionality

• High-level tasks

• Patient creation

• Patient lookup

• data retrieval

• How do sequences of actions complete a task?

• Task sequence and completion indicators

• Wizards

• Titles/screen layout

Semantic Visibility



• Conceptual (definition from Foley & Van Dam text, 1st edition)

• key application concepts that must be understood by user

• User model

• Objects and classes of objects

• Relationships

• Operations

• Example: text editor

• objects = characters, files, paragraphs

• relationships = files contain paragraphs contain chars

• operations = insert, delete, etc.

Conceptual Visibility Myers http://www.cs.cmu.edu/~bam/uicourse/830spring13/830-09-softorg.pptx




Feedback

Action without impact is potentially problematic.

as is reducing complex set of actions to one piece of

information (done/failed)

or, lack of feedback on long-running actions

Don't know if your action has taken place or not

so, you do it again

Therac 25



Errors, Mistakes, Slips

Slips – you know what to do, but you do the wrong thing

!

Mistake – incorrect mental model

!

Examples ? Slips? Mistakes?



How to tell the difference?

"Mistakes are based on difficulty in underlying mental model "But, mental models aren't visible "Must elicit model from user "“think-aloud” protocols –User describes actions, goals, ideas, as they do the work.

" Statements that suggest a mental model might be inconsistent with system model → mistakes



System Capabilities

Execution, Evaluation, Mistakes, Slips

User Goals

Gulf of Execution - interface design

Intentions Action Specification

Interface Mechanism

Gulf of Evaluation - information design

Interface Display

InterpretationEvaluation

SlipsMistakes

SlipsMistakes



How to redesign to avoid slips?



How to redesign to avoid slips?

Clarity in labeling?

!Clear affordances

Mapping

Visibility

Feedback..

!Undo!



Redesign to avoid mistakes?



Redesign to avoid mistakes?

Preferred approaches:

Revise the system model to meet the user model

Revise work and information flow.

!Acceptable:

Increase visibility, feedback, mappings of the system

model

!Not mutually exclusive!



Slips and Mistakes in Clinical Informatics

Why so important?

!

Factors that distinguish clinical informatics from other settings?

!

“To Err is Human” 1999 – Institute of Medicine



A cognitive taxonomy of medical errors Zhang, et al. 2004

System Hierarchy !U = f(u,c,t,s)

U → usability

u → user

c → context

t → task

s → system



A cognitive taxonomy of medical errors Zhang, et al. 2004


Usability - cognitive Factors - Baobab Health Trust, March 2014

Education

Transcript of Usability - cognitive Factors - Baobab Health Trust, March 2014