Psychology 384
Human Factors Laboratory
The Psychopathology
of Everyday Things
Today’s sources: Don Norman
Things That Make Us Smart
 Turn Signals are the Facial Expressions
of Automobiles
 The Design of Everyday Things
(formerly:
The Psychology of Everyday Things)

The Psychopathology
of Everyday Things
Why are some common things
so hard to use?
 Doors
 Stoves
 Faucets
 Light switches
 Refrigerators
 (you name it!)
How to open a door
Operating a door
???
Affordances:
Norman: the perceived and actual
properties of things in the environment
that determine just how those things
might be used by a human being
Affordances provide clues for forming
mental models.
Key to bad design:

Look for a sign!
ATTENTION
The light level in this room is controlled
by pushing the numbered buttons.
Number 1 = 100% (Brightest)
Number 2 = 75%
Number 3 = 50%
Number 4 = 25% (Dimmest)
Number 5 = 0% (Off)
DO NOT USE “ON”/”OFF” BUTTON
DO NOT USE ANY OTHER BUTTON
WITHOUT INSTRUCTIONS
The Design Follies prize:
Welcome to the Del Mar Post Office vending
machine.
I refund a maximum of $3.25 change with
your purchase.
Think before depositing a bill larger than $5.
(This kind of situation, from which there is
no recovery, has been called
a dead end or “deadly embrace”)
Human factors in the cockpit
$$$
 Complex, high-tech setting
 The consequences of errors can be
disastrous

Human factors in the cockpit
Some sources of errors and disasters:
Social interaction among the flight crew
 Automatic controls
 Badly designed controls
 Information overload

Why things don’t work
Designer
User
System
Why things don’t work
Designers fail to take users’ perspective
 Form is rewarded over function
 User studies take time and resources
 Good design is iterative:

Observe
Design
Why things work
as well as they do:

The principle of MAPPING:
Natural vs. arbitrary mappings
Example: Shape coding

Seat adjustment control for a
Mercedes Benz
Stove burner controls
Stove burner controls
Stove burner controls
Stove burner controls
Why things work
as well as they do:
The principle of MAPPING:
Natural vs. arbitrary mappings
 The principle of FEEDBACK

Why things work
as well as they do:
The principle of MAPPING:
Natural vs. arbitrary mappings
 The principle of FEEDBACK
 FORCING FUNCTIONS
(Designing for error)

Forcing functions help prevent errors
A refrigerator’s helpful diagram:
Normal settings
Colder fresh food
Coldest fresh food
Colder freezer
Warmer fresh food
Off (fresh fd & frz)
A B C D E
Freezer
C and 5
C and 6-7
B and 8-9
D and 7-8
C and 4-1
0
1. Set both controls
2. Allow 24 hours
to stabilize
7 6 5 4 3
Fresh food
A mental model:
Freezer
Freezer control
Cooling unit
Cold air
Fresh food control
Fresh food
Cooling unit
Cold air
The real model:
Thermostat
Control A
Freezer
Valve
Cold air
Cooling unit
Fresh food
Control B
User-centered system design:
Some principles
(from Norman)
Represent the required knowledge in
the world (not in the head)
 Provide appropriate feedback
 Use the power of natural and artificial
constraints: physical, logical, semantic,
cultural
 Test with real users (not w/ designers they know too much!)

Intuitive design
has all the virtues of theft
over honest toil.
- Alan Newell,
quoting Bertrand Russell
Roles of cognitive psychologists
in industry:
1. Collecting data
(observations & experiments)
2. Designing things
3. Giving advice
What HCI psychologists do:
Design help systems, documentation,
dialogs, and screen representations
 Act as advocates for users and ideas
 Predict the success or failure of designs
 Observe users and suggest changes
 Compare alternatives
 Advise marketing and engineering folk
 Help make design tradeoffs

Tradeoffs are made between:
powerful, complicated systems vs.
less powerful but easy to learn systems
 time vs. money
 speed vs. functionality or resolution
 changing one part of the interface may
make an enormous difference in
usability (for better or worse)

What HCI psychologists do:
Test new products w/ focus groups
 Study effects of technology on
individuals and organizations
 Develop and prototype new ideas
 Research new uses of technology visualize the future

(cont.)