03 users models

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

A clarification

User’s model
Let’s know our users and how they work

Very complex connections!

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

The man who mistook his wife for a hat
Oliver Wolf Sacks 1933 –2015)

Memories
• • Sensorial memory
• • Short term memory (STM)
• • Long term memory (LTM)
AKA Working Memory

The model

Persistence

SENSORIAL MEMORY

Sensorial memory
• Buffer associated to senses
• RAW information, no elaboration
• It does not require attention
• Limited information persistence:
• – View: <1 sec
• – Hear: 2-4 sec

1
5
STM: short term memory

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

7±2
George Armitage Miller 1920-2012

1
Kim’s game

1
Brown e Peterson experiment (1954)
https://en.wikipedia.org/wiki/Brown%E2%80%93Peterson_task

roberto dadda
7 letters
AKGULSV

2
And now...
Count back 3 by 3 from 15 to 1
Which where the letters??

2
3
15 letters
KRGXORTDQBNMRJK

2
4
15, but meaningful
williammcmillan

2
5
6 words
cat, dog, wife, milk, house, car

2
6
9 words
cat, dog, wife, milk, house, car,
mouse, water, honey

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

STM
• Designed to close tasks as soon as possible,
delete information to make memory available for
other tasks
• Anxiety reduces STM availability

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

Fail!
Microsoft Word 97

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!

LTM: Long Term Memory

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

3
4

Hermann Ebbinghaus Bremen 1850 – Breslavia 1909

3
7

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]

Stephen Wiltshire https://www.nationalgeographic.com/science/article/autism-artist-stephen-wiltshire-cities-genius

4
1
https://en.wikipedia.org/wiki/Atkinson–Shiffrin_memory_model

Stage theory model
4
2
Sensorial
memory
Long term memory
Short term
memory
Stimulus
forgotten
Retrieval
Elaboration
&
storage
Voluntary action
repeat
repeat

4
3
Link
to
an
article
Reactions
timing

Brain computing power!
http://calvino.polito.it/~bacciotti/biciumir.pdf

roberto dadda
4
5
Feedback is important!
Giving a feedback brain has more
infos and makes less errors

Feed-back and motion learning
4
6
Errors
Trials
Quantitative feed-back
Qualitative feed-back
NO feed-back

roberto dadda

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)

Link to an article describing Fitts work

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

5
3
Changes, but not much, with tool
Douglas Engelbart SRI !964

Good usability
comes from a
mixup of
different factors

5
5 Memory and Fitts law tells
us that best menus are…
• Pie
• Popup
• Pull down

5
6
Pie

5
7
Popup

5
8 Pull down

Usability
Roberto DADDA
roberto@dadda.it
www.dadda.it
Skype, Facebook e Twitter robertodadda

03 users models

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03 users models