Chapter 1 Cognitive psychology concepts Jeff Offutt https://www.cs.gmu.edu/~offutt/ Chapter 1, 1.2-1.8, Concepts 1-8

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

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

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

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

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

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

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 Email and paper mail 19-Feb-19 © Offutt

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 email … dropbox New functionality and novel syntax breaks the mental model Always confusing, but sometimes valuable 19-Feb-19 © Offutt

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

Interfaces should conform to the user’s mental model UIs and Mental Models Telephones : I want to call Mom, not 1-606-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

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

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

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

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