Lectures for the course "Ergonomics applied to the usability of web pages and apps" held at the School of design of Politecnico di milano in the first semester of 2021-2022 academic year
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03 users models
1. www.dadda.it roberto@dadda.it Excellence in usability 1st semester 2021-2022 1
ERGONOMICS APPLIED TO THE DESIGN OF USABLE WEB
PAGES AND APPS
Roberto DADDA and Paolo NEGRI
7. www.dadda.it roberto@dadda.it Excellence in usability 1st semester 2021-2022 7
Phineas Gage (1823-1860)
“his wife and
other people
close to him
soon began to
notice dramatic
changes in his
personality.”
Freeman Lobotomy
Chloropromazine (Torazine) 1952
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Memories
• • Sensorial memory
• • Short term memory (STM)
• • Long term memory (LTM)
AKA Working Memory
16. www.dadda.it roberto@dadda.it Excellence in usability 1st semester 2021-2022 16
1
Short term memory
• 7±2 “elements” capacity:
Miller’s magic number (1)
• Short persistency: 20-30 sec
• Repeating and giving
attention makes it last longer
• Used also as a temporary
buffer for cognitive processes
• New inputs recovers others
(1)
https://en.wikipedia.org/wiki/The_Magical_Number_Seven,_Plus_or_Minus_Two
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2
7
9 words, but meaningful
The quick brown fox jumps over the lazy dog
abcdefghijlmnopqrstuvz
Ma la volpe col suo balzo ha raggiunto il quieto Fido
Portez ce vieux whisky au juge blond qui fume
https://en.wikipedia.org/wiki/The_quick_brown_fox_jumps_over_the_lazy_dog
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STM
• Designed to close tasks as soon as possible,
delete information to make memory available for
other tasks
• Anxiety reduces STM availability
29. www.dadda.it roberto@dadda.it Excellence in usability 1st semester 2021-2022 29
STM: implication in UX design
• Avoid surcharging STM asking to memorize large
quantities of unfamiliar terms
• Do it special when you ask to perform potentially stressful
actions like problem solving and decision making
• Avoid when possible stressful situations
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3
1
Let the system do all the task that can perform
Good UX design moves activities from user’s brain to computer whenever
possible!
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LTM
Virtually limitless capacity
Based on meaningful associations
Access made easy by:
Access frequency
Short time from last access
number of associations
Lack of interference by similar associations
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Notable examples of memory super-users
Anatolij Evgen'evič Karpov - Zlatoust 1951
Giovanni Pico dei conti della Mirandola e della Concordia, noto aka Pico della Mirandola 1463 - 1494]
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Stephen Wiltshire https://www.nationalgeographic.com/science/article/autism-artist-stephen-wiltshire-cities-genius
42. www.dadda.it roberto@dadda.it Excellence in usability 1st semester 2021-2022 42
Stage theory model
4
2
Sensorial
memory
Long term memory
Short term
memory
Stimulus
forgotten
Retrieval
Elaboration
&
storage
Voluntary action
repeat
repeat
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roberto dadda
4
5
Feedback is important!
Giving a feedback brain has more
infos and makes less errors
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Feed-back and motion learning
4
6
Errors
Trials
Quantitative feed-back
Qualitative feed-back
NO feed-back
49. www.dadda.it roberto@dadda.it Excellence in usability 1st semester 2021-2022 49
Fitts law
The time needed to move your hand to a target of dimension S at a
distance D is proportional to the relative precision D/S (Index of difficulty)
52. www.dadda.it roberto@dadda.it Excellence in usability 1st semester 2021-2022 52
In pages design
Fitts’ law states that the amount of time required
for a person to move a pointer (e.g., mouse cursor)
to a target area is a function of the distance to the
target divided by the size of the target.
https://www.interaction-design.org/literature/topics/fitts-law
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5
5 Memory and Fitts law tells
us that best menus are…
• Pie
• Popup
• Pull down