‘The Design of Everyday Things’.

Donald A. Norman.

“Design is the successful application of constraints until only a unique product is left”

• You will soon know these important concepts for designing everyday things- Affordances

- Visibility

- Feedback

- Mapping

- Conceptual models

- Constraints

- Consistency

Affordances“the perceived and actual properties of

the thing, primarily those fundamental properties that determine just how the thing could possibly be used”

• Affordances provide strong clues to the operation of things.

• Chairs support therefore, affords sitting on.

• Buttons are for pressing• No picture, label or instruction is

required

Handles are for lifting, but these are for scrolling!

Feedback

Sending back information to the user on what has been done.

The user should receive full and continuous feedback about results of actions.

Imagine drawing with your eyes closed…

‘Feedback is a well known concept in the science of control and information theory’.

D Rosenberg

Feedback

Delays in feedback create confusion and lack of confidence in user.

Feedback

Audio, Tactile, Visual,

Output – digital, sensors, mechanical actions etc

Mikael Fernstrom – earcons

Krispin Laydon – Vibro tactile search.

Constraints• limitations of the actions possible,

perceived from object’s appearance provides people with a range of usage possibilities

Which side? Push or pull?Can only push,side to push clearly visible

Constraints are ways of restricting the kinds of actions a user can take.

Physical constraints – the objects size or shape stops certain actions from occuring

Logical consrtaints – relys on common sense (gravity)

Cultural constraint – localised signals

Mapping

The relationship between two things.

• visible mapping and mimic diagrams: stove and controls

• cause and effect: steering wheel-turn right, car turns right

Good mappings 

It is possible to determine the relationships between:

 

• Actions and results (Cars)

• Controls and their effects (VisiBreath)

• The system state and what is visible (hourglass cursor)

Visibility

• the thing that happens right after an action is assumed by people to be caused by that action

False causality - incorrect effect

invoking unfamiliar function just as computer hangs causes “superstitious” behaviors

Effects are visible only after Exec button is pressed•Ok does nothing!•awkward to find appropriate color level

invisible effect– command with no

apparent result often re-entered repeatedly

– e.g., mouse click to raise menu on unresponsive system

Conceptual Models

 A conceptual model allows the user to

simulate the operation of the device.A good conceptual model allows the user to

predict the effects of their actions. Therefore; Making things visibleBy looking, the user can tell the state of the

device and the alternatives for action.

Uses spatial and mechanical reasoning

Can this function as a bicycle for two?

People often refer to this as having a,

Mental map

Or

Mental model

Transfer effects

• people transfer their learning/expectations of similar objects to the current objects

• positive transfer: previous learning's also apply to new situation

• negative transfer: previous learning's conflict with the new situation

Localised ExpectionsPopulations learn idioms that work in a certain

way, red means danger?

green means safe?

Light switches

America: down is off

Britain: down is on

Faucets/Taps

America: anti-clockwise on

Britain: anti-clockwise off

Designing good concepts

communicate model through visual image– visible affordances, mappings,

and constraints– visible causality of interactions– cultural idioms, transfer– instructions augments visuals

DesignModel

Designer

User's model

User

System

System image

Consistancy

Be consistant in your design choices!

Good Design: Scissors

• affordances: – holes for something to be inserted

• constraints: – big hole for several fingers, small hole

for thumb

• mapping: – between holes and fingers suggested

and constrained by appearance

positive transfer and cultural idioms– learnt when young– constant mechanism

conceptual model: – implications clear of how the

operating parts work

Bad Design: Digital Watch

• affordances: – four push buttons to push, but not

clear what they will do

• constraints and mapping unknown– no visible relation between buttons,

possible actions and end result

• transfer of training – little relation to analog watches

• cultural idiom– somewhat standardized core

controls and functions– but still highly variable

• conceptual model:– must be learnt

Why?

Endeavors to provide an understanding of both the human user and the computer system, in an effort to make the interactions between the two easier and more satisfying.

– many so-called human errors are actually errors in design

– human factors became important as human performance limitations are reached when handling complex machinery

• Britain 1976 – Motorway communication system

operated 40% of it’s highways

– police controlled it in real time to • change lane signs, direction signs, speed

limits, etc

– On December 10th, police failed to change the speed limit signs when fog descended

• 34 vehicles crashed

• 3 people killed

• 11 people injured and trapped in their vehicles

• motorway closed for 6.5 hours

• Police (at inquest)– “The system did not accept the

instruction”

• Dept of Transport (after examining computer logs)– “There is no evidence of

technical failure”

• System designers– after emphasizing that they have

no responsibility for the system• “We supplied it over 5 years ago

and have never been called to look at that problem”

• The Coroner’s court– judged it as "operator error"

• the police operator: “failed to follow written

instructions for entering the relevant data”

Caller: Hello, is this Tech Support?“

Tech Rep: Yes, it is. How may I help you?

Caller: The cup holder on my PC is broken and I am within my warranty period. How do I go about getting that

fixed?

Tech Rep: I'm sorry, but did you say a cup holder?

Caller: Yes, it's attached to the front of my computer.

Tech Rep: Please excuse me if I seem a bit stumped, it's because I am. Did you receive this as part of a promotion at a trade show? How did you get this cup holder? Does it

have any trademark on it?

Caller: It came with my computer, I don't know anything about a promotion.

It just has '4X' on it.

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