‘the design of everyday things’. donald a. norman. “design is the successful application of...
Post on 15-Jan-2016
234 views
TRANSCRIPT
‘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.
Hit Any Key to Continue!