Norman Chapter 1 Psychopathology Jeff Offutt, edited by Paul Ammann https://www.cs.gmu.edu/~pammann/ SWE 205 Software Usability and Design

Psychopathology Huh ? Anybody know what that means? the study of mental illness or mental distress the manifestation of behaviors and experiences that may be indicative of mental illness or psychological impairment Translation: Everyday designs have pathologies 18-Apr-19 © Jeff Offutt

Basic Concepts Well designed objects are simple to interpret and understand They match our expectations Visibility : The correct parts to any object must be visible and must convey the correct message Door handles should not be hidden Mapping : How what you want to do maps to what you can do Think about the mapping for the class seating chart 18-Apr-19 © Jeff Offutt

Basic Concepts (2) Affordance : The properties of an object in relation to an agent (user)—especially the fundamental properties that determine how it can be used What can the specific user do with the object? Affordances vary by user! A typical chair is for sitting, although perhaps not by very small children We say, “This chair affords sitting (by adults)” A chair is also for moving from place to place, but perhaps not by a frail person Glass affords seeing through (for an agent with sight) 18-Apr-19 © Jeff Offutt

A UI that requires a user manual has already failed Basic Concepts (3) Signifier : Communicates what action should take place The vertical bar on the door signifies an affordance: an agent can pull the door open. “In design, signifiers are more important than affordances.” (page 19) False signifiers abound (this is usually bad…) A UI that requires a user manual has already failed 18-Apr-19 © Jeff Offutt

A UI that requires a user manual has already failed Basic Concepts (4) Correlation : Two things happen at the same time Causality : One thing causes the other Humans naturally mix these No, cold weather does not give us colds ! Conceptual model : A mental simulation of how something works A UI that requires a user manual has already failed 18-Apr-19 © Jeff Offutt

Basic Concepts (5) Mental model : How the user expects something to behave If the UI does not match the mental model … fail Natural mapping : Using physical analogies and cultural standards to map the UI to the implementation Feedback : Telling the user that something happened, and what 18-Apr-19 © Jeff Offutt

Why is Designing UIs Hard ? Good UIs take time to design Many programmers are lazy Designing a good UI requires thinking like the user instead of an engineer Engineers often think they are users Different users want different things Engineers love features They want to do everything the technology allows! 18-Apr-19 © Jeff Offutt