Fitting the machine to the user and fitting the user to the machine
Prologue: Names and definition
A. Other common names for the field:
Human factors engineering
But the best one to use: engineering psychology
B. Definition: the science of
(a) Designing machines for human use and
(b) Determining appropriate behaviors for the efficient operation of machines.
Machine: include all nuclear to laptop to a cup.
This definition highlight the two goals that led to development of the field:
-> fitting the machine to the user
-> fitting the user to the machine
Part 1: Historical development:
The story begins just before WW2.
A. Design the machine and ignore the user: is not an effective approach!
e.g. with WW2:
o Design of Army tanks: such as too much noise level, the driver couldn’t communicate
with the others as navigator! The visibility was really poor, impossible to see
immediately around the tank. It wasn’t uncommon to hit a stone or fall in a gap. Also,
the seating positions caused back and neck injuries (enough to require medical
attention)!! So more damage to operators than enemy! (lack of consideration against
people you actually use the machine)
o Altitude displays in airplanes: too complex (took 7 sec to read; misread 12% of the
So engineer begins to take a different approach such as:
B. Design the machine and then “fit” the user to the machine.
1. Select people who fit the machine.
- If strength required, select strong users.
- If intelligence required, select intelligent users.
NB: It’s how industrial psychology started, fit people in the job.
Problem: not always possible to find people who fit the machine: e.g. the women during
the WW2: in weapons factory women were not very productive. Why? Because the
machine worked! There are more explications:
- Not smart enough? NO - Machines were originally designed for men, women didn’t fit the machines (but no
men to use the machine)
2. Train people to use the machine:
- give pilots more training with altitude displays
- “time and motion” studies: train workers to move more efficiently when using machines
(eliminate unnecessary movement)
- Training was time consuming and expensive to provide.
- Machines were becoming so complex that no amount of training would be effective
(they exceeded human capabilities to operate them).
Engineering psychologists suggested that we have to change the user because the machine is already
designed! We can’t change the machine! But they thought that we don’t have to considerate the
machine as something that cannot be change!
C. Design the machine so it fits the user:
1. Two early examples that it can be done:
o Taylor (1898): changing the design of shovels can increase productivity.
o The Gilbreths: can increase “movement efficiency” by redesigning machines and
the workplace. E.g. :
- Using scaffolds (échaffaudage) when laying bricks (poser des briques)
- Put shelves in fridge doors
- Put foot pedal on trash cans
- Have nurses provide instruments to surgeons
2. Additional examples that designing machines to fit the user must be done (1980’s)
(a) Technological disasters:
o Three Mile Island (1979): a nuclear power plant in US comes very close to
o Bhopal, India (1984): chemical spill kills 400 injures 200,000
o Chernobyl (1986): explosion at nuclear power plant kills 300; contaminates
millions of acres
What do they have in common? Human factors were ignored when the technology was designed.
The control room at three Mile Island are very very complex!!! (google a picture). Complexity is made
worse by the poor layout of controls. Operator has to reach for controls with support from his hand
(pour toucher un bouton haut il doit s’appuyer sur la console, et s’il touchait un bouton de la
console!!!). Operator needs a special ladder to see some of the controls. What if ladder is in wrong
place at a critical moment???
(b) An increase in product liability and personal injury lawsuits:
- Poorly designed products can cause injuries
- So products must be designed to be safe (don’t change the user, change the
(c) The development of personal computers
- E.g., command line interface required learning a new language. E.g., to underline ctl
U you have to tape all the word. - Difficult to learn; easy to make mistakes.
- The apple Macintosh’s approach: they changed