Designing for the Real World Material from /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 a terminal in early December causing chaos at the London Stock Exchange. The error at stockbrokers Greenwell Montagu led to systems staff working through the night in an attempt to cure the problem” InfoWorld, December 1986 In 1988, the Soviet Union’s Phobos 1 satellite was lost on its way to Mars, when it went into a tumble from which it never recovered. “not long after the launch, a ground controller omitted a single letter in a series of digital commands sent to the spacecraft. And by malignant bad luck, that omission caused the code to be mistranslated in such a way as to trigger the [ROM] test sequence [that was intended to be used only during checkout of the spacecraft on the ground]” Science magazine

People vs machines Design 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 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