1. psychological and physiological constraints
Week 5 – 2014 HCI – COMP3315
psychological and physiological constraints

2. People: psychological and physiological constraints
First Principles of Interaction Design (Revised & Expanded) March 2014

3. A challenge for HCI lectures… lecture notes versus the experience
People learn more if they engage eg have to click to see the information, have to think about issues and use information rather than just read it.
Human cognition…. Impact on assignment

4. Overview Thinking about people Some theories and terms
Cognitive
Physical
Physiological
Some theories and terms
Mental models
Gulf of execution
Conceptual models
Fitts’ Law
Some very fine-grained guidelines, useful for design and for no-user Heuristic Evaluation
Importance of empirical validation of all theories

5. Mental models
Definitions, links to most other parts of HCI, valuable language and mental tools

6. Mental models http://www.nngroup.com/articles/mental-models/
Summary: What users believe they know about a UI strongly impacts how they use it. Mismatched mental models are common, especially with designs that try something new.
Definition: A mental model is what the user believes about the system at hand.
Note:
Beliefs …. Not facts
Mental models drive predictions, planning actions
Individual MMs differ …. Designer MM versus “user” MM
MMs change…. Implications for One Sentence Statement

7. Example: “Cannot save file…. No space”

10. Mental models…. What was the user’s mental model?
What is the designer’s (actual) system model
Cause of the problem???
How to overcome it???
In this case
In general

11. The refrigerator challenge
Your refrigerator’s freezer section is not cold enough
You find a dial at the back of the freezer labelled as below and set on 3
warmer colder
What will you do? Will it work? What is your mental model?

12. Neilsen on MM
….many less-techy users don't understand the differences between many other common features:
Operating-system windows vs. browser windows
A window vs. an application,
Icons vs. applications,
Browser commands vs. native commands in a Web-based app
Local vs. remote info
Different passwords and log-in options (users often log in to other websites as if they were logging in to their )
Implications for
usable security?
Building on metaphors

13. How to address…
“Make the system conform to users' mental models — …. This is the approach we usually recommend to fix IA problems:
eg If people look for something in the wrong place, then move it to the place where they look for it.
Card sorting is a useful way to discover users' mental model of an information space so that you can design your navigation accordingly.
Improve users' mental models so that they more accurately reflect your system.
eg explaining things better
making labels clearer to make the UI more transparent (even though the underlying system remains unchanged).

14. Some useful distinctions
Slips:
correct user model, inadvertent incorrect action
eg car “malfunction”, tap caps lock accidentally
Mistakes: incorrect mental model
Use this tightened vocabulary for your think-aloud reports

15. Norman’s Gulf of Execution http://learnline. cdu. edu

16. Norman’s Gulf of Evaluation http://learnline. cdu. edu
Gulf of evaluation: the amount of effort required to determine the system state
When problems occur in the evaluation phase, the "gulf of execution" widens
Some examples
"What happened then?"
"What did I do wrong"
User repeats the action (e.g. clicks the NEXT or SUBMIT button)

17. Norman’s Gulf of Execution http://learnline. cdu. edu
Gulf of execution….distance between the user's goals and
the means of achieving them through the system
Some examples:
"What do I do now?"
"How do I [...]?"
"I wanted to [...], but I can't see how I would do that?"
"Do I press this?"
"Do I type this in here?"
"I'm looking for [...] but I can't find it"

18. Norman’s Gulf of Execution http://learnline. cdu. edu

19. Overcoming gulfs - Norman’s questions : Norman, D. A
Overcoming gulfs - Norman’s questions : Norman, D.A.  1988  "The Design of Everyday Things."  MIT Press
How easily can a person determine:
1 determine the function of the device?
2 tell what actions are possible?
3 determine mapping from intention to physical movement?
4 perform the action?
5 tell  what state the system is in?
6 tell if system is in desired state?
7 determine mapping from system state to interpretation?

20. Principles of good design
Provide a good conceptual model
Enables user user to build good mental model of the device.
And to predict the effects of their actions.
Make things visible/audible/tangible
Ensure user can see, hear, feel… the state of the device and the alternatives for action.
The Principle of Mapping
Relies on linking existing mental model to perceived system
Natural mapping
Physical analogies
Cultural standards
The Principle of Feedback
Information on what has been accomplished or is doing.
full and continuous feedback about results of actions.

21. Mental versus conceptual models http://uxmag
“…. a mental model refers to the representation of something—the real world, a device, software, etc.—that the user has in mind. It is a representation of an external reality. Users create mental models very quickly, often before they even use the software or device. Users’ mental models come from their prior experience with similar software or devices, assumptions they have, things they’ve heard others say, and also from their direct experience with the product or device. Mental models are subject to change. Users refer to mental models to predict what the system, software, or product is going to do, or what they should do with it.

22. [eg] iPad ebook … mental model about ..
“… A conceptual model is the actual model [available] to the user through the interface of the product.
[eg] iPad ebook … mental model about ..
what reading a book will be like in the iPad,
how it will work, what you can do with it.
But when you sit down with the iPad, the “system” (the iPad) will display …. screens, and buttons, and things that happen.
The actual interface is representing the conceptual model. Someone designed a user interface and that interface is communicating to you the conceptual model of the product.

23. Case study Moded interfaces:
The same interface action has a different meaning depending upon the context
Class activity: define some examples of moded interaction in common interfaces eg text editor, Powerpoint, Word
What are the challenges for the user?

24. Redraw this, adding conceptual model, and making changes to correct any errors

25. Challenges for design:
conceptual model doesn’t match the user’s mental model
designers of the conceptual model needs to account for the user’s mental model
How does CI help?
And the role of Think-Aloud?
multiple user groups
conceptual model purely reflects underlying hardware, software or database
creating materials/training to build an appropriate mental model
One Sentence Statement?

26. Returning to Assignment 1
Why are sketches better for exploring the space of conceptual models?
Some students used software for wireframes and prototyping – why is this dangerous?
Clarity on differences between mental model, conceptual model, actual system

27. Fitts’ Law

28.
time …. to complete the action
a and b are empirically determined regression coefficients,
…..values gained from direct observation that build a slope.
distance … from the starting point to the …target object
width is the width of the target object

33. Age matters

34.
Participant in (1) was a 4 year 6 month old female.
Participant in (2) was a 5 year 8 month old female.
Participant in (3) was a 21 year-old female.

35.
All paths taken by 5 year old participants to click on a 32 pixel target at a distance of 256 pixels.

36.
All paths taken by adult participants to click on a 32 pixel target at a distance of 256 pixels.

37. Beyond the mouse?

38. Grouping, layout, hierarchies
Fitts’ Law in action –
Grouping, layout, hierarchies

39. The prime pixel……where your cursor is now
Fitts’ Law in action –
The prime pixel……where your cursor is now

40. Windows, …. right-click …
Windows, …. right-click ….contextual menu of options usually appears that has its point of origin at the prime pixel.

41. Magic pixels….. What are they? Fitts’ link? Why are they important?

42. Summary Empirical foundations Heuristics for designers
Grouping items for flow of action
Special locations
Prime pixel
Magic pixels

43. A Quiz Designed to Give You Fitts http://www. asktog
Microsoft Toolbars offer the user the option of displaying a label below each tool. Name at least one reason why labeled tools can be accessed faster. (Assume, for this, that the user knows the tool and does not need the label just simply to identify the tool.)
You have a palette of tools in a graphics application that consists of a matrix of 16x16-pixel icons laid out as a 2x8 array that lies along the left-hand edge of the screen. Without moving the array from the left-hand side of the screen or changing the size of the icons, what steps can you take to decrease the time necessary to access the average tool?
A right-handed user is known to be within 10 pixels of the exact center of a large, 1600 X 1200 screen. You will place a single-pixel target on the screen that the user must point to exactly. List the five pixel locations on the screen that the user can access fastest. For extra credit, list them in order from fastest to slowest access.
Microsoft offers a Taskbar which can be oriented along the top, side or bottom of the screen, enabling users to get to hidden windows and applications. This Taskbar may either be hidden or constantly displayed. Describe at least two reasons why the method of triggering an auto-hidden Microsoft Taskbar is grossly inefficient.

44. A Quiz Designed to Give You Fitts http://www. asktog
Explain why a Macintosh pull-down menu can be accessed at least five times faster than a typical Windows pull-down menu. For extra credit, suggest at least two reasons why Microsoft made such an apparently stupid decision.
What is the bottleneck in hierarchical menus and what techniques could make that bottleneck less of a problem?
Name at least one advantage circular popup menus have over standard, linear popup menus.
What can you do to linear popup menus to better balance access time for all items?
The industrial designers let loose on the Mac have screwed up most of the keyboards by cutting their function keys in half so the total depth of the keyboard was reduced by half a key. Why was this incredibly stupid?
What do the primary solutions to all these questions have in common?

45. Attention

46. Attention
Daniel Simons

47. Attention Why did this happen? What is attention?
Visual **
Audio
What are the implications for UI designers?
Multi-tasking
Attention-grabbers
And for UI evaluations?
Eye tracking
Think-aloud
For your project
Guiding the user in where to attend

48. Memory Working memory Long term memory WM very limited
Miller, George A. "The magical number seven, plus or minus two: some limits on our capacity for processing information." Psychological review 63.2 (1956): 81. (>17K gcites, Sep 2013)
WM very limited
Chunking is really important
Complex to user this to predict … but may explain think-aloud observations
(Claude Shannon theory of information .. Brain as information processing machine)
Long term memory
Critical for recall at UI
And learning about UI
Mental model

49. Perception Translating external stimuli into the memory
Senses
Processing their information
Tightly interlinked physical and cognitive
Simple example, reading a screen
Vision… visibility

50. Screen design
Tullis, Thomas S. "The formatting of alphanumeric displays: A review and analysis." Human Factors: The Journal of the Human Factors and Ergonomics Society 25.6 (1983):
Key outcomes in terms of
Performance versus affect (preferences)
Density (local/overall), grouping, layout complexity
Grouping related elements, organised for vertical scanning, with space between them aids search in speed and preference
Science of screen design
Careful empirical studies
Design of initial study
Replication
Impact of different technology
Impact of the particular task
Impact of user’s mental model, standards for device, application
Translation to your interface

51. Colour Valuable for screen design
Performance ++
Affect ++
Well understood challenges that are avoidable but failure to do so can compromise performance

52. Tog Principles http://asktog.com/atc/principles-of-interaction-design/
“Principle: Any time you use color to convey information in the interface, you should also use clear, secondary cues to convey the information to those who cannot see the colors presented
Principle: Test your site to see what color-blind individuals see
Principle: Do not avoid color in the interface just because not every user can see every color.
Principle: Do not strip away or overwhelm color cues in the interface because of a passing graphic-design fad.

53. Colour blindness Affected ~ 8% of men, .5% women Tetsting tools eg
For images images
xxxx

54. Coblis — Color Blindness Simulator Their demo: normal vision

55. Green-Blind/Deuteranopia

56. Blue-Blind/Tritanopia

57. Red-Blind/Protanopia

58. Normal vision

59. Blue-Weak/Tritanomaly

60. What can you do about colour blindness?
Be aware!
Design in black and white and add colour sparingly
What else? …. Class activity

61. Colour Valuable for screen design
Performance ++
Affect ++
Well understood challenges that are avoidable but failure to do so can compromise performance

62. Coding Means distinguishing different parts of an interface Includes
Font changes such as these
Font with style and size
Use of colour such as here and here – seriously
Special symbols, shapes
Sound
Movement
All are about ...

63. Coding Means distinguishing different parts of an interface Includes
Font changes such as these
Font with style and size
Use of colour such as here and here – seriously
Special symbols, shapes
Sound
Movement
All are about ... gaining attention

64. Colour can be poorly used
Means distinguishing different parts of an interface
Includes
Font changes such as these
Font with style and size
Use of colour such as here and here – seriously
Special symbols, shapes
Sound
Movement
All are about ... gaining attention

65. Stroop effect

66. Stroop Effect
From

67. Colour Properties Hue – wavelength (red .. violet)‏
Saturation, chroma (purity, mix of wavelengths)‏
High saturation very pure
Low saturation, greyish
Brightness, intensity, value
very low intensity becomes black

68. CSE 440: User Interface Design, Prototyping, and Evaluation
Visible Spectrum
Winter 2013
CSE 440: User Interface Design, Prototyping, and Evaluation

69. Physiology and colour Rods and cones
Fovea – detailed vision (eg text)‏
Only cones sensitive to colour
64% respond to red
32% to green
2% to blue (none in fovea!)‏
Opposing colours at the neuron level
Red-green, yellow-blue

70. Visual acuity reduced for violet end of spectrum
Insensitivity to blue increases with age
Blue seems harder to read, especially on some backgrounds
With normal light, we see mid-spectrum colours best (ie green, yellow)‏
Colour blindness
8% men, 0.4% women
Use additional redundant cue eg colour + box + brightness difference and this improves broad performance

71. Reds appear closer than blues
Warm colours appear larger than cool colours
eg red larger than blue
Blooming effect
Light colours on dark backgrounds appear larger
Colours distant on spectrum require refocusing
After images and shadows can follow
Opposing colours
Highly saturated colours
Illumination matters too

72. Light text on a dark background
Dark text on a light background

73. Blooming – light text on dark background seem larger
Light text on a dark background
Dark text on a light background
Blooming – light text on dark background seem larger

74. Red text on a dark background
Red text on a light background

75. Red text seems to focus differently

76. Red text seems to focus differently

79. So many ways to make mistakes...

80. CSE 440: User Interface Design, Prototyping, and Evaluation
Color Guidelines
Avoid simultaneous display of highly saturated, spectrally extreme colors
e.g., no cyans/blues at the same time as reds, why?
refocusing!
desaturated combinations are better  pastels
Winter 2013
CSE 440: User Interface Design, Prototyping, and Evaluation

81. CSE 440: User Interface Design, Prototyping, and Evaluation
Using the Hue Circle
Pick non-adjacent colors
opponent colors go well together
(red & green) or (yellow & blue)
Winter 2013
CSE 440: User Interface Design, Prototyping, and Evaluation

82. eg http://colorusage.arc.nasa.gov/guidelines.php
Guidelines eg

83. Examples:
Pure blue shall not be used on a dark background for text, thin lines, or high resolution information. [Source: DOE-HFAC 1, 1992] FAA Human Factors Design Standard, p 8-58
Blue. Blue should not be used as the foreground color if resolution of fine details is required. [Source: DOD HCISG V2.0, 1992] FAA Human Factors Design Standard, p 8-57.

85. More examples from NASA: from http://colorusage. arc. nasa
Use no more than six colors to label graphic elements.
Use colors in conformity with cultural conventions.
Use color coding consistently across displays and pages
Use color coding redundantly with other graphic dimensions.
Don't use color coding on small graphic elements

86. Recommendations Use colour sparingly
Maximum codings 5 (+ or – 2) matching short term memory
Design in monochrome first
Optimise all other aspects of design and layout
Add colour (with awareness of problems)‏
Use colour to:
Draw attention (better than shape, size, brightness)‏
Show organisation, status, relationships

87. cont With black foreground, use cyan, magenta, white
Ensure contrast ib hue and brightness of fore- and background
Allow users to control colour coding
Use colour consistently across system
Use other (redundant) cues as well
Avoid saturated blue for small text and thin lines

88. Blinking and movement
When is it good?
And not?

89. Take yourself back to hunter and gatherer times:
A hungry tiger is coming from the distance at your right

90. Blinking and movement Hard to ignore Reduces legibility
Can be really annoying
Helpful for tiny cursors (otherwise hard to find and large ones are obtrusive)‏
Helpful for critical situations

91. Shapes Conventions for some shapes Special shapes Cultural boundaries
eg warning and errors
Special shapes
eg little hand pointing
Cultural boundaries

92. Summary Awareness of human factors affecting design
Awareness of some basic guidelines for use of colour
Apply these for a simple form of no-user testing by checking your UI against guidelines
Better done by person other than designer (role for your teams to desk-check each other’s designs)