By: Dr. Magdy Akladios
1/25/2006
SENG 5334: Human Factors Engineering
&
INDH 5931: Research Topics in IH/Safety
Chapter 3: Information Input &
Processing
By: Magdy Akladios, PhD, PE, CSP, CPE, CSHM
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Information Acquisition
z Information is the key to survival.
z Information can be:
{External: about our external world, Acquired by
exteroceptors (5 senses - vision, audition,
olfaction, tactile, gustation)
{Internal: about our state, Acquired by
interoceptors (e.g. kinesthesis, proprioception)
z The brain must sift this constant information
stream for relevant cues (Signals) rather
than irrelevant cues (Noise).
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What is Information?
Information is the reduction
of uncertainty
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By: Dr. Magdy Akladios
1/25/2006
Information Theory
z Quantifying Information
z Highly probable events convey little
information and merely confirm what we
anticipate
z Highly improbable events convey greater
information because they are not anticipated
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Bits
z Information is measured in BITS (H)
z 1 Bit is the amount of information required
to decide between 2 equally likely
alternatives
z H = log2N
z Where, N = Number of equally likely
alternative
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Examples:
z If Head or a Tail are equally likely
alternatives, then: H = log2N = log2 2 = 1
bit
z If there are 4 alternatives, H = log2 4 = 2
z If there are 8 alternatives, H = log2 8 = 3
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By: Dr. Magdy Akladios
1/25/2006
Non-equi-probable Information
z When alternative choices are not equiprobable, then the information associated
with an event (Hi) is:
{Hi = log2 (1/pi) where pi = probability of i
z For a series of events of differing
probabilities:
{Hav = ∑[pi (log21/pi)]
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Example
z Assume 2 events of unequal probabilities,
p1 = 0.9 and p2 = 0.1
z Hav = {[0.1(log21/0.1)]+[0.9(log21/0.9)]} =
0.332 + 0.137 = 0.469 bits
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Redundancy
z Redundancy is the reduction in information
from the maximum information because of
unequal probabilities of occurrence
z % Redundancy = (1 - (Hav/Hmax) x100
z From previous example:
{% Redundancy = (1-[0.47/1.0] x 100 = 0.53 x100 = 53%
z Because certain letter combinations are highly
probable (th, qu, st), and others highly improbable
(cw, tx, xq) the English language is ~68%
redundant.
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By: Dr. Magdy Akladios
1/25/2006
Bandwidth
z Bandwidth is the rate of information
transmission over a channel.
z Bandwidth of the eye is ~ 1,000 bits/sec
z Bandwidth of the ear is ~ 10,000 bits/sec
z Bandwidth of the brain is a limited single
channel capacity system.
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Displaying Information
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Display Design
z There are principles of perception that
apply too each of the senses.
z Ignoring the principles of perception can
create dysfunctional information displays.
z Knowledge of the principles of perception
helps us to design more effective
information displays
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By: Dr. Magdy Akladios
1/25/2006
Sources of Information
z Directly
z Indirectly:
{Coded
{Reproduced
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What is a Display?
z Any form of Indirect presentation of
information
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Types of Displays
z Static display
z Dynamic display
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By: Dr. Magdy Akladios
1/25/2006
Types of Information Presented by Displays
z Quantitative Information
z Qualitative Information
z Status Information
z Warning & Signal Information
z Representational Information
z Identification Information
z Alphanumeric & Symbolic Information
z Time-lapsed Information
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What type(s) of information
are these?
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1/25/2006
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By: Dr. Magdy Akladios
1/25/2006
Selection of Displays
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Use Auditory Presentation if:
1.
2.
3.
4.
5.
6.
7.
8.
The message is Simple
The message is Short
The message is Will not be referred to later
The message is Deals with events in time
The message is Calls for immediate action
The visual system of the person is overburdened
The receiving location is too bright or too dark
The person’s job requires moving about
continually
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Use Visual Presentation if:
1.
2.
3.
4.
5.
6.
The message is Complex
The message is Long
The message is Will be referred to later
The message is Deals with location in space
The message does not call for immediate action
The auditory system of the person is
overburdened
7. The receiving location is too noisy
8. The person’s job allows him to remain in one
position.
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By: Dr. Magdy Akladios
1/25/2006
Coding of Information
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1/25/2006
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What’s are the difference(s)
between the two shapes?
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By: Dr. Magdy Akladios
1/25/2006
Absolute vs. Relative Judgment
z Absolute:
{making a distinction without a reference point
z Relative:
{making a distinction with regards to a reference
point
z The Magic Number: 7 +/- 2 (5-9)
z Improves by Training
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Making Absolute Judgment along Multiple
Dimensions
z Orthogonal Dimensions:
{The value of one dimension is independent of
the value of the other
{Example: Shapes: Squares and Circles, Colors:
Red and Green.
z Redundant Dimensions:
{Knowing the value of one dimension helps
predict the value of the other
{Example: Shapes/Colors: Only Red Squares
and Green Circles.
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What Type of Dimension is this?
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By: Dr. Magdy Akladios
1/25/2006
Characteristics of a Good Coding System
1.
2.
3.
4.
5.
Detectability of codes
Discriminability of codes
Meaningfulness of codes
Standardization of codes
Use of multidimensional codes
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Meaningfulness of Codes Exercise
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Compatibility
z Compatibility refers to the relationship of
stimuli and responses to human
expectations.
z Stems from intrinsic situations, or are
culturally acquired.
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Types of Compatibility
1.
2.
3.
4.
Conceptual Compatibility
Movement Compatibility
Spatial Compatibility
Modality Compatibility
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1. Conceptual Compatibility
z Deals with the degree to which
codes/symbols correspond to conceptual
associations people have
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By: Dr. Magdy Akladios
1/25/2006
2. Movement Compatibility
z It relates to the
relationship between
the movement of
displays/controls
and the response of
the system being
controlled.
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3. Spatial Compatibility
•Refers to the
physical arrangement
in space of controls
and their associated
displays.
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4. Modality Compatibility
z Refers to the fact that certain stimulusresponse modality combinations are more
compatible with some tasks than with
others.
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