Chapter 2 Foundations of usability Jeff Offutt https://www.cs.gmu.edu/~offutt/ Chapter 2, 2.2-2.5, Concepts 2-5

Users anthropomorphize software Fundamental Concept 2 Users anthropomorphize software by expecting it to behave as if it is human We name our tools We curse at our home assistants We expect software to be considerate, thoughtful, and rational 27-Apr-19 © Offutt

Knowledge in the world and knowledge in the head Fundamental Concept 3 Users look for knowledge both in their heads and in the world Some knowledge that may not be in your head Write down the names of your country’s states or provinces Whose face is on a $20 bill? $50? Giving directions is much harder than walking to it We merge knowledge in our heads with knowledge in the world We often do not need to be precise Good UIs constrain our use with syntax—legos, electronic connections, radio buttons 27-Apr-19 © Offutt

Information In the Head Information In the World Information that we memorize Our own name Our address World Information that we see or look up Time Courses offered next semester We often move information from one place to another Our class schedule The room number for our class 27-Apr-19 © Offutt

Precision is Not Needed People are not good at being precise The one dollar coin was almost the same size as a quarter—The US made this mistake twice in my life! Remembering 10-digit phone numbers is hard … so my phone has a contact list and voice activation The French & Indian war occurred about 20 years before the US revolutionary war … but which year? We learn to be precise in our field only after years of learning and practice A good UI must not require precision But should help the user find precision when required 27-Apr-19 © Offutt

Syntactic Constraints Spelling is hard … but made easier by patterns What consonants can precede an “h” ? “ch”, “gh”, “ph”, “rh”, “sh”, “th”, “wh” Singers, musicians, dancers and martial artists don’t memorize so much as recreate based on patterns that “make sense” The syntax of a UI must make syntactic constraints clear In PPTX, if I highlight text, lots of actions are immediately enabled 27-Apr-19 © Offutt

Visibility, mapping, and functions Fundamental Concept 4 Controls must be visible, the features they control must be obvious (mapping), and their effect must be clear (functions) Invisible controls slow down learning Unclear mappings slow down learning and increase errors This is hard because designers don’t get confused But users do 27-Apr-19 © Offutt

Mapping Syntax to Semantics This arrangement has a natural mapping … fewer mistakes ! How can we remember which control maps to which burner ? Mistakes are encouraged 27-Apr-19 © Offutt

Design usable defaults Fundamental Concept 5 Most users never change the defaults, even if another option would improve usability Users assume designers considered defaults carefully with their best interests in mind Sometimes Other time defaults are essentially random And sometimes they are for the company’s benefits Social media make more money from public settings We can’t choose good defaults until we understand the users Designers are NOT typical users 27-Apr-19 © Offutt

Foundations of usability 5 measurable criteria Users anthropomorphize software Knowledge in the world & in the head Visibility, mapping, and functions Defaults 27-Apr-19 © Offutt