3. Why Consider Human Factors?
• Enhance efficiency (productivity)
• Ensure safety
• Assure tasks are within human capability
• Improve human performance
• Gain market acceptance
• Reduce costs (economic, legal, social)
4. Human in the Human factors:
• Humans are involved in all aspects of technology
– Designers
– Users (operators)
– Maintenance personnel
• The problems of technology failure:
• machine failure
• human error
• interaction of humans and machines (system
error)
5. Physical Ergonomics Vs Cognitive
Ergonomics
• Physical ergonomics focuses on our bodies
• Cognitive ergonomics is interested in what
goes on in our brains:
– the way our senses perceive information
– the way in which we understand and interpret it
– what determines the decisions we make
6. COGNITIVE ERGONOMICS
• Studies cognition in work settings, in order to
optimize human well-being and system
performance
• Focuses on the fit between human cognitive
abilities and limitations and the
machine, task, environment
7. Goals of Cognitive Function
Aims at enhancing performance
of cognitive tasks by:
User-centered design of human-
machine interaction and human-
computer interaction
Design of information technology
systems that support cognitive tasks
(e.g., cognitive artifacts)
Development of training programs
Work redesign to manage cognitive
workload and increase human
reliability
8. • The way people perceive and act has direct
implications for the design of the artefacts and
environment that they use
Mind is as comfortable at work as the body
• If physical surroundings reflect and support their
natural cognitive tendencies,
Less errors
performance & productivity -positive boost
9. SELECTIVE ATTENTION
Limited ability to transmit
information
Allocation of attention
If not selectively attend to
individual aspects of the Factors for attention failures :
tasks, performance –
impossible
1)Attentional capacity & demands
Failures to notice & attend to 2)Expectations
displays, warnings - human
3)Stimulus salience
errors n accidents
10. Attention-al capacity:
Most fundamental constraint
Attention is single, undifferentiated but limited
resource(kahneman ,1973)
Use sensory channel that have spare capacity
Eg : primary task -vision (driving) –more use of auditory
displays
Task related work load :
Extremely high or low workload – less attentive
11. Expectations:
• Less likely to notice unexpected stimuli
• Perceptual confusions
• see or hear what they want to ….
• Solution in such situations is to increase
salience of important information
12. Stimulus Sailence:
• Lights - brighter
• Tones & sounds - louder
• Movement & changes in intensity
eg: use of flashing lights, freq modulated tones,
waving flags
So as to capture the attention during task
performance
13.
14.
15.
16.
17. EXAMPLES OF COGNITIVE IN
APPLICATION:
• Designing a software interface to be "easy to
use“
• Designing a sign so that the majority of people
will understand and act in the intended
manner
• Designing an airplane cockpit or nuclear
power plant control system so that the
operators will not make catastrophic errors
18.
19. Cognitive Ergonomics Introduction:
• Cognitive ergonomics studies cognition in work
settings
• In order to optimize human well-being and
system performance
• An emerging branch of ergonomics that places
particular emphasis on the analysis of cognitive
processes
• Cognitive processes:
– Diagnosis
– Decision making
– Planning
20. Broad Definition of Cognitive :
• The configuration of equipment and furniture
in a hospital operating room to maximize
team performance and minimize errors of
perception, attention and judgment
• The design of a commercial jet’s cockpit to
correspond to the crew’s natural tendencies in
perception, memory, and decision making
21. Cont……
• The creation of an office environment to
minimize distractions and maximize
productivity and performance
• The arrangement of a classroom to maximize
information exchange, knowledge
creation, and acquisition
25. Models Of Cognitive Ergonomics:
• Recent models of cognitive ergonomics
involve three dimensions:
• Usefulness
• usability
• acceptance
26. Usability:
• The degree to which a product or service is
easy to use, easy to learn, and optimized for
efficiency
• ISO 9241-11 “Guidance on Usability”
• Extent to which a product can be used by
specified users to achieve specified goals with
effectiveness, efficiency and satisfaction
27. Cont…..
• Effectiveness - Accuracy and completeness
with which users achieve specified goals
• Efficiency - Resources expanded in relation to
the accuracy and completeness with which
users achieve goals
• Satisfaction - Freedom from discomfort, and
positive attitudes towards the user of the
product
28. • Related fields
• Human-computer interaction
• NeuroErgonomics
• Supervisory control
29. Neuro- Ergonomics
• Using Brain Function to Enhance Human
Performance in Complex Systems
• - The scientific study of brain mechanisms and
psychological and physical functions of
humans in relation to technology, work, and
environments
30. • “N`euro-ergonomics Adaptive Human-Machine
involves the Systems
• examination of the neural
bases
• of perceptual, cognitive
and motor
• functions in relation to
real-world
• applications as mediated
through Machines.”
31.
32.
33. Design In Human Equipments With
Ideal Cognition Controls
• Why this Course is Not
Human Factors Design • Design of Safe and
Automated Cockpit in
Boeing 777
• Design of a safe and
useful infusion pump
34. Because Minds and Brains are “Situated”—in a Body
and Environment with artefacts and
Tools—Hence Cognitive Engineering
37. Activities in Human memory
• PERCEPTION:
• complex sensory processes
• primary images containing all information about the concrete
features of objects (visual, acoustic, etc)
• MEMORY:
• ability to remember, recognize and recall
• information is encoded, stored and retrieved.
• active: structuring, constructive and creative psychic mechanism.
• THOUGHT: the process of information processing in working
memory
40. POOR ERGONOMICS IN DESIGN AND
PERCEPTION
• Driving at night in Santa Cruse
takes a little bit of extra attention.
The street lights emit yellow light
instead of the more typical bluish
white. Actually, I think the yellow
street lights use less electricity
too. The problem is that sometimes
it is difficult to tell whether a light
is a yellow street light or a yellow
traffic light. The photo shows a
view down a Santa Cruse street
with an arrow pointing out two
green traffic lights
41. CAR DRIVING IN MUMBAI
• In contrast, the same photo
shows the same view with
yellow traffic lights. Notice
how the yellow traffic lights
look similar to the street
lights. Imagine you are
driving along at night and
don't notice that the yellow
lights ahead are yellow traffic
lights. You might be very
surprised when they turned
red. I wonder if this causes
traffic accidents?
42. Why doesn't this marker cap fit?
• Why weren't the kids putting the caps on
their colored markers after using them? I
noticed that after unsuccessful attempts to
put on the caps, they just left the markers
uncovered. Sometimes even I had difficulty
putting on the marker caps. A closer
examination of a marker cap revealed the
problem: both ends of the cap look the same.
At a glance it looks like the marker can be
inserted into either end of the cap. Actually
the marker will fit into only one end of the
cap. The incorrect end of the cap does not fit
either end of the marker.
The correct end of the cap does have a
slightly raised ring around it, a feature
which you may learn to identify. Initially,
however, this subtle clue does not help you
get the cap on correctly.
43. IDEAL DESIGN CAP
• The incorrect end
should not appear as if
the marker could be
inserted. This could be
accomplished most
naturally by blocking
the opening on the
incorrect end like these
other marker caps.
44. Objectives in Cognition Ergonomics:
• shorten the time to accomplish tasks
• reduce the number of mistakes made
• reduce learning time
• improve people’s satisfaction with a system
45. • Cognition is the processing of environmental
information acting on the environment
• Any available system that processes
information in its environment to act upon it
could be called “Cognitive System” and
performs “cognitive work”.
46. Knowledge Interpretation
• Procedural : information corresponds to knowledge of how to do something
• Declarative : information corresponds to knowledge of facts
Levels of task performance ( given by Rasmussens):
Different forms of information - used at each level of performance
Skill based: automatic processing of signals , no conscious control –seen in various sensory
motor tasks like tracking a moving object with your eyes or steering a vehicle
• Rule based :sequential cuing of responses by consciously perceived cues or signs, eg: when a
stop light changes from red to green, people decide to go.
• Knowledge based:
more laborious
clear formation of plans for attaining some goal
involves meaningful manipulation of symbols
47. • Products and environment - designed to provide signals & cues - easily
perceived, easily discriminated and valid indicators of conditions,
functions, hazards & misuses.
• Information transmission
Depends on both :
Information sent & its effect on receiver
eg: A speedometer - display the current speed of a vehicle -very high, look at
it , slow down - you realize you are speeding
50. Human-Computer Interaction
HCI involves the study, planning, and design of the interaction between
people (users) and computers.
• Supporting knowledge on both the computer and the human
• Computer side - techniques in computer graphics operating
systems, programming languages and development environments - relevant
• Human side - communication theory, graphic and industrial design
disciplines, linguistics, social sciences, cognitive psychology and human factors
such as computer user satisfaction - relevant
• Interaction occurs at the user interface which includes both hardware and
software
51. Cont….
• Collaboration to perform a task, to do Cognitive Work
The flow of information between the human and computer - loop of interaction
including:
• Task environment: The conditions and goals set upon the user
• Machine environment: The environment that the computer is connected to, e.g. a
laptop in a college student's dorm room.
• Areas of the interface: Non-overlapping & overlapping areas
• Input flow: begins in the task environment, user has some task that requires
computer use
• Output: originates in the machine environment
• Feedback: Loops through the interface that evaluate, moderate, and confirm
processes as they pass from the human through the interface to the computer and
back
52. 2. Intervention areas
Design
• The process that happens from the conceptualization
of the artefact until when it is used by the people for
whom it is intended
• 2 main aspects in system design(Carroll, 1991).
“The process" of design itself
How people devise a new system, what are the factors
involved in making decisions
53. Technological innovation
Ergonomists "proactively" supply ideas and
empirical data for the design of future artefacts improving human
performance and public acceptance of new technologies.
• The concept of "user-centered design" developed in 1980´s in the
design of technologies (Norman, 1986)
• Aims at describing the human being interacting with the system
from the viewpoint of cognitive science
• Eg : Essential elements of user centered design of a web site - visibility,
accessibility, legibility and language
54. • Visibility
constructs a mental model of the document
• Accessibility
To find information quickly and easily throughout the document, regardless of
its length.
Navigational elements, search functions, table of contents, clearly labeled
sections, page numbers, color-coding etc.)
Chunking - useful strategy
Legibility
• Easy to read useful font style
• Ornamental fonts and text in all capital letters ,italics and bolding - helpful when
used correctly.
• High figure-ground contrast between text and background increases legibility
• Dark text against a light background is most legible.
55.
56.
57.
58. Cont….
• The allocation of functions to both humans
and artefacts
• The design of the interface through which
humans and artefacts communicate while
collaborating in performing the task
59.
60. Adaptive Functions
• Human and artefacts interact to perform a
task by performing cognitive functions
• Therefore, the design of interaction is to
describe how these cognitive functions are
allocated to humans and artefacts
• “Adaptive function allocation” to mean that
functions could be re-allocated through the
interaction
61.
62.
63.
64. Functional Analysis:
• The first cognitive level: sensory-motor
– interaction is described from the point of view of the
characteristics of the human sensory and motor
systems
• Interaction occurs when the output of the
device, be this visual, auditory, or of any other
physical type, is captured by human sensory
receivers
• Human behavior would be processed through the
motor system, and it is essential that the device
has the necessary input systems to receive it in
the appropriate way
65. Design phase
• Cognitive ergonomics is promoting "user-
centered design", in the sense that users are
integrated in the design process as early as
possible
• “ User centered design addresses early and
continuous focus on users, empirical
measurements, interactive design and
multidisciplinary design teams
66.
67. Evaluation Phase:
• User centered design involves iterative design,
so that evaluation is conducted at every stages
of development.
70. Mental workload and stress
• Whenever a person is faced with a task - implement some cognitive
resources leading to a variety of functional states that are known
“mental workload”, “fatigue", "stress” etc - work performance
• Mental and physical health
• Development of specialized human-computer interfaces intend to
reduce the demands for cognitive resources.
• Sometimes tool developed to assist people impose additional
burden - excessive stress and loss of situation awareness
71.
72. WHAT IS MENTAL WORK LOAD ?
Mental workload is the portion of operator’s limited mental
capacities actually required to perform a particular task.
Mental reserves are the difference between capacity required
and capacity available.
Mental effort is the voluntary matching of mental capacities
with that needed for task success.
Increase in Mental Workload often precedes Performance
Failure.
74. Primary Task Techniques
• Measures the Performance Outcome as
• a function of Primary Task Demand
How well are you Flying? How well are you Driving?
75. Primary Load Techniques
As task load increases, the additional demands on mental
capacities result in a degradation in performance
• Advantages of This Measure:
• Workload reflected directly by performance outcome.
• Non-invasive and non-interfering.
• Tracks changes in workload dynamically. (i.e., as performance proceeds)
• Uncontaminated by memory issues
• Disadvantage of This Measure:
• Only sensitive to changes in workload at the limits of mental capacity
• If operators can compensate for increased workload by increasing their
• Effort, the primary task measure is insensitive
• Mental Workload not distinguished from performance outcome
76. Cont…
• What About Failure?
• Most of the time we’d like
to know about Mental
Workload to know how
much is too much?
• Primary Task measures do
not tell us this.
• So, - they fail to be
informative just at the time
they are needed most!
77. Bad Ergonomic Design :
Example: Tractor
Forwarding Units,
South African
Forestry Industry
Original Unit: Poor
operator seating and
visibility
78. Re-designed With User In Mind :
Tractor-Trailer
Forwarding Units
South African Forestry
Industry
Redesigned Unit: Good
operator
seating and visibility
79. Workload and Vigilance
• Vigilance is a Long-Standing
Problem.
• Sources of Performance Influence
Include:
1. Event Rate
2. Signal Salience
3. Stress/Workload/Fatigue
4. Glare, Noise, Temperature, Vibration, TOD,
Drug Effects etc
5. Memory Load
6. Successive vs. Simultaneous Comparisons
7. Feedback
8. Hit vs. Miss vs. FA KR/KP
9. Individual Differences
10. Introversion/Extraversion, Age, Sex,
Expertise
80.
81. WHY DO ERRORS HAPPEN ?
• Person approach
– Blame the individual for forgetfulness, inattention,
weakness
– Countermeasures: write another procedure,
disciplinary measures, threat of litigation, retrain, blame,
shame.
• System approach
– Multiple faults that occur together in an unanticipated
interaction create chain of events in which faults grow and
evolve.
– Countermeasures: based on assumption that though we cannot
change the human condition, we can change the conditions
under which humans work (e.g., system defenses
82. What is a Poorly Designed System?
• One that
– Does not match the needs of a human being or
task
– Does not take into account human limitations
(perception, memory, anthropometrics).
84. Systems Approach:
• Two principles:
– Same set of circumstances can provoke similar
errors, regardless of the people involved.
– Safety is seriously impeded if an organization does
not seek out and remove the error provoking
properties within the system at large.
85. Human Error
• What is an error?
– Failure of a planned action to be completed as intended (error
of execution) or use of a wrong plan to achieve an aim (error of
planning).
• Active failures (sharp end)
– Occur at the level of the frontline operator
– Effects are felt almost immediately.
• Latent conditions (blunt end)
– Tend to be removed from the direct operator control
– Result in two kinds of adverse events:
• Error provoking conditions within the local workplace
(e.g., time pressure, understaffing, inadequate
equipment, fatigue, inexperience)
• Create long-lasting holes in defenses (e.g., design
deficiencies, untrustworthy alarms, unworkable procedures
86. • Example:
– Active error: The pilot
crashed the plane.
– Latent error: A
previously
undiscovered design
malfunction caused
the plane to roll
unexpectedly in a way
the pilot could not
control and the plane
crashed.
88. ERROR MANAGEMENT :
• Limiting errors
• Creating more error-tolerance
• High reliability organizations capable of…
– Performing exacting tasks under pressure
– Carrying out activities with low incident rates
– Good organizational design and management
– Organizational commitment to safety
– High levels of redundancy
– Strong organizational culture
– Converting occasional setbacks into enhanced resilience of the
system.
89. Safety and accident investigation
• Errors - not caused by irresponsible behaviour or
defective mental functioning
May be a consequence of not having taken into
account ,how a person perceives, attends,
remember, makes decisions, communicates and
acts in a particularly designed work system
90. • Investigating the causes of human errors by
analyzing the characteristics of human
information processing
• classification of errors according to the level of
processing involved in the behavior
• Jens Rasmussen (1983) - 3 types of errors
depending on the level and degree of cognitive
control involved in the erroneous behavior
91. • Errors based on skills: familiar with the task, actions – over learned as a low-level
pre-programmed sequence of operations - do not require a conscious control
o If one of these actions is poorly performed or the sequence is applied in an
unusual order.
• Errors based on rules: The selection of actions in a situation often depends on the
implementation of a set of rules of the type IF(condition) THEN (action)
o The activation of the right rules depends on the interpretation of the situational
conditions
o If a situation is misinterpreted the retrieved rule will be inappropriate as well
92.
93. Situation awareness and attention
• The processes of conscious perception and understanding of the
situation
• complex tasks such as flying an airplane, - necessary to process
huge amount of data on what is happening in the cabin , in the air
outside the plane, and even at the airport and the control tower.
• information - attentively handled, retained, interpreted and used
to make necessary decisions for the airplane to fly properly and
landed safely
94.
95. Situational awareness includes three levels of
information processing:
(1) perception of the elements of the environment;
(2) understanding the current situation;
(3) predicting(projecting) the situation’s future
development
96.
97. • Instability of human performance related to the
automation of work processes
• High degree of automation, human operator is out of loop
of controlling processes - operators are less well practiced
in their abilities to take over the process when an
automatic unit fails
• Manual and cognitive skills decline due to the absence of
active participation in the process
• Difficult with progressing automation to gain access to
knowledge about the system behavior
98. Mental Models:
• When interacting with a system, people normally
have some knowledge of its structure and
functioning
• Taking into account the peculiarities of users’
mental models in the design of artefacts is
crucial for an efficient interaction
• Therefore, the investigation of mental models is
one of the central themes in cognitive
ergonomics (Canas, Antolí and Quesada, 2001)
99. • A model that is constructed and simulated
within a conscious mind
• Mental models contain knowledge and help
us create new knowledge
100. Learning with and about artefacts
• After designing a new artefact users must learn to
interact with it
• New artefacts - more complex requiring - more
complex cognitive abilities
• Technological progress is so fast that nobody can
expect to learn to interact with an artefact and
continue using it for long time
• eg:, earlier - typewriters, and now - computers and
text editing programs that have completely changed
• So topic of learning is as important as the topic of
design itself
102. Designing a sign so
that the majority of
people will
understand and act in
the intended manner
103. Cognitive Task Analysis (CTA)
• Provides a formal set of methods for identifying the mental
activities required by a task and an artifact, such as a desktop
computer system
• Identify bottlenecks and critical paths - opportunities for
improvement or risks (such as human error) that merit
changes in training or system behavior.
• Both people and artefacts are jointly regarded as agents .
The focus is on the transfer and processing of information
within and between agents such as the military, air traffic
control, aircraft cabins or navigation systems for large ships.
104. • Cognitive Task Analysis may include:
cognitive interviewing
analysis of verbal protocols
multi-dimensional scaling
computer simulations of human performance
(cognitive simulations)
human error analysis
105. • Understanding of the demands of the work
situation, user strategies in performing cognitive
tasks and limitations in human cognition.
• In some cases, the artifacts or tools used - impose
their own constraints and limitations
(e.g., navigating through a large number of GUI
screens)
• modern artifacts (e.g., control
panels, software, expert systems) are becoming
increasingly sophisticated
106. MAN MACHINE SYSTEMS:
• Man holds key position(decisions)
• Recording display – information about the progress of production -eg.
fluctuations of temp. or pressure throughout a chemical production
• Operator receives this inform visually (perception)
• Must understand and assess correctly (Interpretation)
• On d strength of his interpretation & in d light of his previous knowledge-
takes a decision
• Communicate this decision to machine by using controls
• Control display tells operator the result of his actions eg how much water
is mixed with the reagents
• Machine then carries out the production process as programmed
107.
108. • Man & machine - combine to form a very
productive system, - their respective qualities are
sensibly used.
• Proper communication.
• Operator tells machine, what to do, using
controls & input devices and he is told what to do
and what not to do by display’s, sign’s, signals
and other information
• Extent to which messages from a machine are
correctly communicated - very imp - large impact
on product quality & usability
109. When more elaborate controls & higher output (like in
development of electronics)
Consequently -high need for accurate interpretation of
the information displayed
Operators task - more delicate and more demanding
eg:
In an aircraft d speed of pilot’s reaction can be vital
In chemical process alertness & correct decision
taking may alone avert the catastrophe
110. • So man machine system needs to be ergonomically
sound
• The points of interchange from man to machine & from
machine to man interfaces- very imp
• Ergonomic interfaces of man machine system:
Perception of all information on display
Manually operating the controls
111. COGNITIVE CONTROLS :
• Big machines in industry, agriculture, transport - control panel -
many similar controls & it is important to be able to pull the right
lever or turn the right knob, sometimes even without seeing it.
• Therefore controls that might be mistaken for each other should be
so designed- identified without difficulty –can be assured by:
• Proper arrangement- like in sequence of operation or difference
between vertical & horizontal movements
• Structure & material- like knobs of different shapes & size,
difference in surface texture(smooth, ridged etc)-helpful if control
has to be handled unseen
• Color & labeling
• Controls - certain minimum distance apart to be operated freely &
correctly
• Resistance - some amount of resistance to operation- less likely to
be triggered off by a slight movement.
112. Cognitive Modeling
• Produce a computational model for how people perform
tasks and solve problems, based on psychological principles
• These models may be outlines of tasks written on paper or
computer programs which enable us to predict
the time it takes for people to perform tasks,
the kinds of errors they make,
the decisions they make or
what buttons and menu items they choose
113. Model human processor
Predetermined time system which contains the time predictions for
very basic elemental information processing tasks.
• This model predicts median performance times & expected time
ranges for simple cognitive tasks
• Assumes that the task involves a series of sensory & information
processing steps followed by a motor activity
• Each step requires time to be performed
• Total task time is the sum of times required for separate activities
114. • It consists of 3 different processors :
1)Perceptual processor: places visual or auditory image
into a short term sensory store & the corresponding
code into working memory
Median time= 100ms
2)Cognitive processor: checks for matching between
items in working memory, retrieves information from
memory, make decisions & select a response
Median time=70ms
3)Motor processor: executes the physical act decided
upon
Median time=70ms
