Human Factors
Psychology
Lecture 1: Course Introduction
PSY-4340/PSY-5340, Dr. William Langston, MTSU
Gas Pump
How Do I Open This?

Some human factors issues to consider:
The goal of human factors is to optimize system performance
(operator + machine + environment). A 50% failure rate is hardly
optimizing system performance.
(Picture from Darnell, 2003).
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Will’s Rules
1.
2.
The proper way to use a device should
be obvious from looking at it.
Even in a reasonably trivial situation like
this, wasted time and effort are
frustrating and unnecessary. If it really
mattered (like in a car), serious disaster
could result.
The Infamous Ballot
Some
The
human factors issues to consider:
side-by-side presentation is confusing.
No consideration of even minimal visual impairment.
No consideration of even minimal motor impairment.
Why is it possible to punch two if you can only vote for one?
It presents extraneous information (e.g., the numbers).
Will’s Rules
1.
2.
3.
You have to consider every potential
user, not just young, tech-savvy people
with perfect vision.
You have to anticipate common
mistakes the user might make and
prevent those mistakes.
Nothing the user does should result in
a catastrophic error. Ever.
Popping the Trunk

Some human factors issues to consider:
Physical limitations also need to be considered in
design. When hiding controls, keep in mind that
fingers have less visual acuity than eyes.
(Picture from Darnell, 2003).

Will’s Rules
1.
You have to consider the everyday use of
an object when planning its design. Will
it work as intended in the heat of the
moment?
Hubris
* Customer: "I'm looking at the back of the system, and I don't know
where to plug in the mouse. There are two holes that are the same size
as the mouse."
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* Tech Support: "Ok, what color is the tip of the mouse plug?"
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* Customer: "Orange."
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* Tech Support: "Do you see the orange 'hole' on the back of the
computer?"
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* Customer: "Yes."
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* Tech Support: "That is where the mouse plugs into."
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* Customer: "Oh. How about the keyboard?"
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* Tech Support: "What color is the plug on the keyboard?"
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* Customer: "Purple."
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* Tech Support: "And do you see the purple 'hole' on the back of the
computer?"
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Etc.
From Stoddard, S., & RinkWorks Productions. (2003). Computer
stupidities: Calls from Hell. Retrieved May 10, 2003 from
http://www.rinkworks.com/stupid/.

You try…
Does the green label go with the top or the
bottom hole? (Ignore the arrows, they’re not
intended to be giving the answer.)
(Picture from Darnell, 2003).

Will’s Rules
1.
2.
Blaming the user is not the same thing as
proper human factors design.
It’s important to step back and think like a
novice user, not a developer/designer. Of
course you know how it works.
Fundamental Attribution Error
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When people make mistakes we tend to make
an internal attribution. In other words, we
perceive people’s mistakes as being their fault.
Research shows that people generally discount
situational pressures that might cause the
average person to make the same mistake.
Even though this is a difficult-to-overcome
human propensity, it’s an important thing to
avoid in design. If you create an error-likely
situation, fix it, don’t blame the victim.
Will’s Ultimate Rule
1.
There’s a big difference between being a
grumpy old man and making a legitimate
point. The goal of human factors is to
improve human/machine interaction.
Most of the time, if you make a mistake
using a product, it’s a design flaw, not a
human flaw.
Human Factors
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Systems approach:
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Operator + machine/device + environment.
Any failure = system failure. That’s to be avoided.
There’s a lot more flexibility in manipulating the
machine/device than in manipulating the operator.
Consequences of failure:
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Bad press (Microsoft).
Lost productivity.
Lost profit.
Serious injury/death.
Human Factors
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Definition:
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“The study of those variables that influence
the efficiency with which the human performer
can interact with the inanimate components of
a system to accomplish the system goals.”
(Proctor & van Zandt, 1994, p.2)
Human Factors

Or:
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“Human factors is that branch of science and
technology that includes what is known and theorized
about human behavioral and biological characteristics
that can be validly applied to the specification, design,
evaluation, operation, and maintenance of products
and systems to enhance safe, effective, and satisfying
use by individuals, groups, and organizations.”
(Christensen, Topmiller, & Gill, 1988, p.7, as cited in
Proctor & van Zandt, 1994, p.2)
Human Factors

Basic human capabilities:
Perceptual
 Attention span
 Memory span
 Physical limitations
 Etc.

Historical Antecedents:
Psychophysics
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Weber (1846):
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Fechner (1860):
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How can we tell that two stimuli differ?
Weber’s Law: D I/I = k.
Application: Recognizing that an indicator light has
come on.
Attempt to produce a scale to relate a physical
stimulus to the sensation produced.
Fechner’s Law: S = k log(I).
Demonstrate the use of empirical methods to
understand human performance.
Historical Antecedents:
Physiology
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Helmholtz:
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Nervous transmission is not instantaneous.
Attach electrodes at two points on a frog leg,
stimulate, look for effect. Difference in time can be
used to compute speed of nervous transmission.
Speed = 27 m/s.
If nervous transmission is not instantaneous,
then we can study components, including mental
components.
Historical Antecedents:
Timing
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Donders (1868):
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Analyze components of speeded tasks:
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Detect.
Identify.
Discriminate target from other stimuli.
Select a response.
Subtractive method: Create tasks that vary by only
one component, compare times in the various tasks
to compute how long each component takes.
We can actually break mental activity into its
component parts. Response time is the handle
on doing this.
Historical Antecedents: Role
of Mental Activity

Wundt (1879):
First psychology laboratory.
 Believed that mental events play a causal role
in human behavior.
 Understand mental by decomposing sensory
and perceptual experience into basic
elements.
 Introspection.
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The method had problems, the ideas are
still with us.
Historical Antecedents:
Memory
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Ebbinghaus (1885):
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Created lists of nonsense syllables,
memorized them, studied properties of
memory (e.g., savings).
Demonstrated empirically that mental
constructs like memory could be studied in
the laboratory.
Historical Antecedents:
Attention
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James (1890):
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Outlined the basic components of attention.
Historical Antecedents:
Information Processing
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We have the basic foundation for a human
information processing approach:
Cognition is a series of operations performed
on information originating from the senses.
 Human factors implication: The human
operator can be analyzed in the same way as
the machine/device.
 For example, a computer has input,
processing, output just like the operator.

Human Factors
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World War II was a major force in bringing all of
this together. New technologies, many
untrained users, and profound consequences of
failure highlighted the critical need for human
factors research.
Find human factors research applied to:
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Military technology.
Nuclear power plants.
Aviation.
Automobiles.
Consumer products.
Human-computer interaction.
Human Factors Psychology
Lecture 1: Course Introduction
End
References:
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The notes are based on Proctor, R. W., & van Zandt,
T. (1994). Human factors in simple and complex
systems. Boston: Allyn and Bacon.
Most pictures and bad design examples are from
Darnell, M. J. (2003). Bad human factors designs.
Retrieved May 10, 2003 from
http://www.baddesigns.com.