Designing for the Real World

Material from

0657.425/525 Human Computer Interaction

Dr Steve Jones

Let’s start with a few challenges...

Suggest designs for a water tap for a bathroom sink a chest of drawers an aircraft’s altimeter

It can’t be too difficult to get it right... can it?

Inspired tap design

Even more inspired drawer design

Altimeter design

Blame the users!Who is to blame?

“An inexperienced computer operator pressed the wrong key on aterminal in early December causing chaos at the London StockExchange. The error at stockbrokers Greenwell Montagu led tosystems staff working through the night in an attempt to cure theproblem”

InfoWorld, December 1986

In 1988, the Soviet Union’s Phobos 1 satellite was lost on its way toMars, when it went into a tumble from which it never recovered.“not long after the launch, a ground controller omitted a single letter ina series of digital commands sent to the spacecraft. And by malignantbad luck, that omission caused the code to be mistranslated in such away as to trigger the [ROM] test sequence [that was intended to beused only during checkout of the spacecraft on the ground]”

Science magazine

People vs machinesDesign for people!

Psychology and design

Important concepts in design visual affordances mappings constraints feedback causality transfer effects stereotypes conceptual models individual differences

Affordances

the perceived and actual properties of an object that determine how it should be used

complex objects may need explanation, simple should not

eg• chair for sitting• knobs for turning• slots for inserting cards/money• buttons for pushing

Mappings

Intuitive relationship between controls and objects?

Constraints

limitations of possible actions perceivable from object’s appearance

Feedback

the change in object state resulting from a user’s action is perceivable from the object

Causality

whatever happens immediately after a user action is assumed to be caused by that action

linked to interpretation of feedback incorrect effect - superstitious behaviours

eg invisible effect - repeated behaviours

eg

Transfer effects

apply existing knowledge/expectations to similar objects

positive transfer : previous learnings apply negative transfer : previous learnings conflict

Stereotypes

…avoid them!

color symbolism charts

Conceptual models

people build mental models of how things work, which influences how they try to use them

built from affordances, mappings, transfer effects, etc......

models may be wrong if attributes of object are misleading

(but we may want to mislead sometimes)

Individual differences

Individual differences let’s design a door! how tall should it be? should we use average height?

Don’t design for yourself

Remember you do NOT necessarily represent a good

average user of equipment or software that you design

do not expect others to think or behave as you do