Lecture BY
Saher Zia
Queries
The Psychopathology of Everyday
Things
•
The human mind is tailored to make sense of the world
•
Give it the slightest clue and off it goes
•
Well-designed objects are easy to interpret and understand. They
contain visible clues to their operation.
•
Poorly designed objects can be difficult and frustrating to use. They
provide no clues—or sometimes false clues.
Opening a milk carton
• Classic example from Austrian TV
• Glass bottles were being replaced by new cartons.
• On live TV, a manager demonstrates how easy it is to open the new cartons. . . • . . . but everything goes rather wrong!
Example of old tractors
•
Works quickly but caused accidents in rough hilly areas
•
Usually called driver’s error
Modern Tractor Design
• Less frequent accidents
Roll Cage
Low Center of Gravity
Which automobile in Pakistan has bad
design that can cause accidents?
Zeiss Slide Projector
Zeiss Slide Projector (cont.)
•
Only one button to control the slide advance.
•
During lectures, sometimes the slides go forwards, sometimes they go
backwards . . .
•
If you can find an instruction manual:
•
Short press = forward, long press = backward.
•
What an elegant design, two functions with just one button!
Car Seat
Car Seat (cont.)
•
A seat in a mini-van (people carrier
•
What do you think happens when you pull the lever under the seat?
•
Most normal-thinking people would expect the seat to slide backward or
forward.
•
Not in this mini-van. Pulling the lever detaches the seat from the floor to make
The Frustrations of Daily Life
Can you use all the functions of your:
1.
digital watch?
2.
mobile phone?
Example of a Remote Control
•
Some of the buttons on a VCR remote control
are easy to understand, but others are
The Psychology of Everyday Things
This topic discusses some principles that constitute the psychology
of human beings that “how they interact with everyday things”
OR
The principles that forms the “mental model” of human beings that
how something works
•
These principles include:
Affordance
• Affordance is the range of possible (physical) actions by a
user on an object:
• Perceived Affordance is the set of actions a user perceives
to be possible.
Affordance (Cont.)
Real World Affordances
• For physical objects, there can be both real and perceived affordances (and the two sets are not necessarily the same).
• Appearance support affordance and indicates how to use something, for example: 1. A chair affords (suggests) sitting.
2. Knobs are for turning.
3. Slots are for inserting things. 4. A button affords pushing.
• When perceived affordances are taken advantage of, the user knows what to do just by looking.
Affordance (Cont.)
• Example of ambiguous doors design
• In door (a) a knob is available for turning but no
clue for push or pull.
• In door (b) a horizontal bar is available but no
clue from which side of the bar to push
Affordance (Cont.)
• Example of good doors design
• In door (a) a vertical bar affords grasping and
pulling.
• In door (b) the broadness of the
bar indicates push and which side
to push
Affordance (Cont.)
Affordance (Cont.)
Affordance (cont.)
Typical Computer Hardware and GUI affordances
examples
1.
Screen affords touching.
2.
Mouse affords pointing.
3.
Mouse buttons afford clicking.
4.
Keyboard affords typing.
•
Changing the shape of the cursor to indicate a clickable link
Mappings
•
Mappings are the relationship between controls and their effects on the system.
•
Natural mappings take advantage of physical analogies and cultural standards and
helps in immediate understanding
•
Examples:
1.
Turn steering wheel clockwise to turn a car right.
2.
Actually, there are two mappings here:
– which control affects steering out of so many controls.
– which direction to turn the steering control to move
right or left.
•
Move a control up to move an object up. (physical analogy)
Mappings (cont.)
• Example of natural mappings
• Which control is connected to which stove?
• Arbitrary mapping, There are 24 possible
Mappings (cont.) [1]
Mappings (cont.)
•
A natural mapping There is no ambiguity, no
need for learning or remembering, and no
Constraints
•
The difficulty of dealing with a novel situation is directly related
to the number of possibilities.
•
Constraints are physical, semantic, cultural, and logical limits
on the number of possibilities.
1. Physical constraints such as pegs and holes limit possible operations. 2. Semantic constraints rely upon our knowledge of the situation and of
the world.
3. Cultural constraints rely upon accepted cultural conventions.
4. Logical constraints exploit logical relationships. For example a natural mapping between the spatial layout of components and their controls.
Constraints (cont.)
• Example of Lego
Constraints (cont.)
•
Physical
: Front wheel only fits in one place.
•
Semantic
: The rider sits on the seat facing forward.
•
Cultural
: Red is a rear light, yellow a front light.
Constraints (cont.)
Constraints
Conventions
• Conventions are cultural constraints. They are initially arbitrary, but evolve and become accepted over time.
• They can however still vary enormously across different cultures, for example: • Light switches:
America down is off Britain down is on
• Water taps:
America anti-clockwise is on Britain anti-clockwise is off
• The colour red: America danger Egypt death India life
Causality
• Causality is when something which happens right after an action, appears to have been caused by that action.
• There are two kinds of false causality: 1. Coincidental effects lead to superstition:
– Touch a computer terminal just before it fails, and you are apt to believe you caused the failure.
– Start an unfamiliar application, just before the computer crashes.
2. Invisible effects lead to confusion:
– When an action has no apparent result, you may conclude it was ineffective (and repeat it).
– For example, repeatedly clicking the “Stop” button when the system is unresponsive.
References
[1] Lecture Notes of Prof. Keith Andrews, Available at: www.iicm.tugraz.at/hci
[2] Design of Everyday Things slides by Saul Greenberg, University of Calgary, Canada, available at: saul.cpsc.ucalgary.ca/public/Lectures/DesignPsychopatholology.pptx
