1. Chapter 1 Cognitive psychology concepts
Jeff Offutt
Chapter 1, , Concepts 1-8

2. Users make mistakes Fundamental Concept 2
Errors of intent are not the same
as errors of execution
Humans are not perfect
Execution: User knows what to do but do it incorrectly
Intent: User doesn’t know what to do
Intentional errors: User did the wrong thing on purpose
Don’t think of users making mistakes
Think of users getting close
19-Feb-19
© Offutt

3. Users learn by scaffolding
Fundamental Concept 3
Users add new knowledge by connecting it to existing knowledge, or scaffolding
Users learn by relating new ideas or knowledge to existing ideas or knowledge
Analogies, idioms, and consistency helps the users find the right scaffold
19-Feb-19
© Offutt

4. Users learn knowledge and skills differently
Knowledge vs. skills
Fundamental Concept 4
Users learn knowledge and skills differently
Knowledge is learned by reading, listening, or watching
Semantic: what do to
Syntax: how to do it
Skills are learned by doing something
Learning a skill connects knowledge to syntax
19-Feb-19
© Offutt

5. Syntactic vs. semantic knowledge
Finding files
find . –name “*.ppt”
Start – Find – Files or Folders …
Searching within files
grep “cat*” filename1 filename2 …
open file1 – Ctrl-F string – close file1; open file2 – Ctrl-F – close file2, …
Firefox & VIM : “/string” is a shortcut
How to describe this?
Regular expression?
Wild card?
19-Feb-19
© Jeff Offutt

6. Syntactic & Semantic
Syntax knowledge is about how to manipulate things, without regards to the concepts
How to type, without knowing language
How to turn a radio on, without understanding the sounds
Semantic knowledge is about the concepts
The language we type in
The meaning of the music and the words
‘thank you,” “xie xie,” “gracias,” “cám ón” all have the same semantics, but very different syntax
19-Feb-19
© Jeff Offutt

7. Computer—Semantic Knowledge
Computer-semantic knowledge is about how the internals of the computer works – the hardware, software platform, etc.
Task-semantic : editing a paper
Comp-semantic : how the file is stored on disk, what printing is, etc.
Users with comp-semantic knowledge learn syntax much faster
Users don’t acquire comp-semantic knowledge by simply using the computer
19-Feb-19
© Jeff Offutt

8. Mental models May or may not be accurate Often omits details
Fundamental Concept 5
A mental model represents a user’s
understanding of how something works
May or may not be accurate
Often omits details
Often based on scaffolding that is only approximate
and paper mail
19-Feb-19
© Offutt

9. Mental models
Fundamental Concept 6
A conceptual model is the actual
model that the interface presents to the user
Differing from the user’s mental model makes it harder to learn
Deleting … dropbox
New functionality and novel syntax breaks the mental model
Always confusing, but sometimes valuable
19-Feb-19
© Offutt

10. Example: Driving a Car When we push the gas pedal, the car goes faster
Mental : Pushing makes it go faster
Implementation : More gas to the engine, more pressure, pistons go faster, tires go faster …
When we turn the wheel, the car turns
Mental : Turning the wheel turns the tires
Implementation : Turning the wheel turns something else (with the help of a motor for power steering), which causes something else to turn, which puts the tires into a different angle
19-Feb-19
© Offutt

11. Interfaces should conform to the user’s mental model
UIs and Mental Models
Telephones : I want to call Mom, not XXX-XXXX
First we must put the phone number into the “world”
Compile : I want to Run my program, not compile, link, run
File Manager : Dragging a file from window to window is :
Move on the same disk
Copy from disk to external devise (USB thumb drive or backup)
Dropbox?
Calendars : Paper calendars require paging, online calendars can scroll
Interfaces should conform to the user’s mental model
19-Feb-19
© Offutt

12. UIs and Mental Models Predicting storms Dice Patriotweb
Does the prediction “30% chance of snow” mean
It will snow in 3 of 10 locations in the area
Less snow than if 50% chance, but more than if 10%
On 3 days out of 10 with these “weather conditions,” it has snowed in the past
Dice
If I roll a 6 five times in a row, what is the probability that my next roll will be a 6 ?
Patriotweb
Login-Faculty&Advisor-Summary Class List-Submit-Submit … Roster …
I expect : Faculty&Advisor-Summary Class List-Submit-Submit … Roster … but no!
19-Feb-19
© Offutt

13. Cognitive dissonance New facts contradict existing facts or beliefs
Fundamental Concept 7
Cognitive dissonance makes learning harder, slows down users, and leads to errors
New facts contradict existing facts or beliefs
This is why it’s so hard for people to change opinions … we lock the first story into our minds
User interfaces that create cognitive dissonance are harder to learn and cause more user errors
19-Feb-19
© Offutt

14. Correlation and causality
Fundamental Concept 8
Correlation does not imply causality
Correlation: When things happen at the same time
Causality: When one thing causes another
19-Feb-19
© Offutt

15. We will refer to these theoretical ideas throughout the semester
Cognitive Psychology
7 2 Rule
Users don’t make mistakes, they get close
Scaffolding
Knowledge and skills
Mental models
Conceptual models
Cognitive dissonance
Correlation and causality
We will refer to these theoretical ideas throughout the semester
19-Feb-19
© Offutt