Ergonomic | System | Body part | cognitive | compactibility | Gaurav Singh Rajput

1. By: Gaurav Singh Rajput
@gauravkrsrajput

2. Literal Definition
Ergon (Work) + Nomos (rules or habits) = “The
rules of work”
Simplest Definition
“Fitting the job to the worker”

3. “ERGONOMICS is the study of the
interaction between people and machines and
the factors that affect the interaction.”
Ergonomics is concerned with designing
and arranging things people use so that the
people and things interact most efficiently and
safely.

5. History Of Ergonomics
Since beginning of time people have been
trying to make everything more efficient with
less stress
In 1857, Wojciech Jastrzebowski created the
word “Ergonomics”
The idea became popular around the industrial
revolution.

6. The name Ergonomics was officially proposed
at a 1949 meeting of the British Admiralty
(July 12), by Prof. Hugh Murrel and was
officially accepted in the year 1950.

7. Purpose:
To improve the performance of
systems by improving human machine
interaction.
This can be done by “designing-in” a
better interface or by “designing out”
factors affecting interaction.

8. Aims Of Ergonomics
Ensures that human needs for safe and
efficient working are met in the design of work
system.
To Design
Appliances
Technical Systems
Tasks
In such a way so as to improve
Human Safety
Health
Comfort

9. Basic Aim Of Ergonomics
Efficiency in the activity.
To achieve desired results without
Waste
Error
Damage to persons
Working situations in harmony with the activities of
the worker.
Approach of Human Factors
The approach of human factors is the systematic
application of relevant information about human
capabilities, limitations, characteristics, behaviour, and
motivation to the design of things and procedures
people use and the environments in which they use

11. Human-Machine Systems
A system is a set of elements, and the
relations between these elements and the
boundary around them.
Most systems consists of people and
machines and perform some functions to produce
an output.
Humans are the part of the system where
they are fully integrated at the design stage.

12. Human Factors 12
Characteristics of Systems
• Systems Are Purposive
• Systems Can Be Hierarchical
• Systems Operate in an Environment
• Components Serve Functions: Every component (the
lowest level of analysis) in a system serves at least one
function

13. A Human-Machine System
Work Environment
Controls
Information
Processing
Human Being Controlling
Displays
Machine
Sensing
Operations
Input Output

14. 14Human Factors
Man-Machine Interface
The Design Engineer can determine the relative
importance of human factors in his design

15. Types of Systems
Manual Systems
Operations controlled by humans with hand
tools and other aids, using own physical energy.
Mechanical Systems
Consists of well integrated physical parts.
Also referred to as semiautomatic systems.
Automated Systems
Fully automated systems with little or no
human intervention.

16. Difficulties in achieving the Aims
of Ergonomics
Human operator is flexible and adaptable
Large Individual differences
Obvious Differences – Physical size, strength
etc.
Non-Obvious Differences –culture, style,
level of skill etc.

17. • System Reliability
Reliability is usually expressed as the probability of
successful performance.
Eg: if an automated teller machine gives out the correct
amount of money 9999 times out of 10,000 withdrawal
transactions, we say that the reliability of the machine, to
perform the function, is .9999. (Reliabilities for electronic
and mechanical devices are often carried out to 4 or more
decimal places; reliabilities for human performance, on the
other hand, usually are calculated no further than 3 decimal
places.)
Another measure of reliability is mean time to failure
(abbreviated MTF).
There are several possible variations, but they all relate to the
amount of time a system or individual performs successfully,
either until failure or between failures; this index is most

18. Improvement of System:
Designing user-interface to make it more
compatible.
Changing work environment.
Changing the task.
Changing the way work is organized.

23. GENERAL MODEL OF THE HUMAN AS AN
INFORMATION PROCESSOR
• A simple model of the human as an information processor
consists of sensory receptors (eyes, ears, nose, etc.) that pick
up signals and transmit them to the processing unit (brain
with storage).
• The results of the processing are output responses (physical,
spoken, written, etc.).

24. Note that up to the information overload point, each input resulted
in an output. For example, 10 inputs resulted in 10 outputs during
the time allowed. When overload was reached, performance began
to decrease. If the overload point, for example, was 40 inputs (with
40 outputs), then 45 inputs resulted in fewer than 45 outputs. In
assessing input overload, it is important to keep in mind the fact
that humans have multiple input channels and these can operate
together (sight, hearing, touch, etc.) to increase input capacity.

25. • Sensory processing: Information and events that occur in the
environment gain access to the brain through our senses (e.g. sight,
sound, smell, touch).
• Perception: Raw data from the environment relayed to the brain must
be interpreted and decoded through a humans ‘perception.
• Cognition: Cognitive processes generally require greater time, mental
effort or attention, as the brain has to carry out processes such as
rehearsal, reasoning or image translation using our working memory.
• Memory
• Response selection and execution: The selection of a response is
separate from the execution of the action, which requires muscle co-
ordination for moving your body to ensure the selected goal is
achieved, whatever that may be.
• Feedback: Feedback loop indicates that actions are sensed by the
human and that the flow of information can be started at any point and
is continuous, feedback establishes that the goal has been achieved.
• Attention: Is the final block in the model, many mental processes are
not automatic, this is where attention comes in, selecting which
process received the limited resources. If you have too many tasks to
perform this can result in divided attention, where one task would
suffer for the other.

26. Cognitive Ergonomics
It deals with cognitive or mental aspects of
ergonomics. These include how your senses
work and how you perceive through them. It also
includes how the brain processes information.
Cognitive Ergonomics deals with Human-
Computer interactions, work stress, mental
workload, decision making, reliability and
training requirements.

27. HUMAN COMPONENTS
The Human body is a part of the physical
world. The goal of Ergonomics is to optimize the
interaction between the body and its physical
surroundings.
Components:-
The Effectors
The Senses
Central Processes

28. The Effectors
Three primary effectors are :-
Hands
Feet
Voice

29. The Senses
These are the means by which we are made
aware of our surrounding. The 5 senses are :-
Sight
Hearing
Touch
Taste
Smell
Vision and Hearing are most relevant to
Ergonomics.

30. Vision is often complimented by
touch.
Example :-
When someone says “Let me see
that”, while at the same time reaching for
it.
Here the word “see” really means “see
and touch”

31. Central Processes
Physiological Processes –provides energy to the
working muscles.
Brain – Information Processes Centre that contains
Low level programs to control basic sensori-
motor work activities.
Higher level process that makes planning,
decision making and problem solving activities of
the work.

32. HUMAN COMPONENTS
 The Effectors
 The Senses
 Central Process
MACHINE COMPONENTS
 The Controlled Process
 Displays
 Controls
 The Immediate
Environment
 Workspace
 The Physical
Environment
 Work Organization

33. Compatibility
Matching demands to capabilities.
“The state at which two or more things are
able to exist or perform together in
combination without any conflict”
Ergonomics Entropy –Disorder in system
functioning due to lack of compatibility in
some or all interactions involving the human
operator.

34. To achieve compatibility we must assess
the demands placed by the technological and
environmental constraints and weigh them
against the capabilities of the Human Operator.
Compatibility can be achieved at the
Biomechanical, anatomical, physiological,
behavioral and cognitive levels.

35. Various reasons for Incompatibility:-
Human requirements for optimum system
functioning were never considered at the
design stage.
Inappropriate task design.
 Lack of prototyping.

36. Requirements
Equipment that is usable and safe.
Tasks that are compatible with peoples
expectation, limitation and training.
An environment that is comfortable and
appropriate for the task.
A system of work organization that recognizes
peoples social and economic needs.

37. COGNITION
• Cognition is the set of all mental abilities and
processes related to knowledge
• attention, memory & working memory,
judgement & evaluation, reasoning &
computation , problem solving & decision
making, comprehension & production of
language, etc.
• Cognition has to do with how a person
understands and acts in the world.
• It is a set of abilities, skills or processes that are
part of nearly every human action.

38. • Cognitive abilities are brain-based skills we
need to carry out any task from the simplest
to the most complex.
• They have more to do with the
mechanisms of how we learn, remember,
problem-solve, and pay attention rather
than with any actual knowledge.
• cognitive abilities are based on specific
neural networks or brain structures.
• For instance memory skills rely mainly on
parts of the temporal lobes and parts of the
frontal lobes (behind the forehead).

39. • For instance, answering the telephone
involves at least:
• perception (hearing the ring tone),
• decision taking (answering or not),
• motor skill (lifting the receiver),
• language skills (talking and
understanding language )
• social skills (interpreting tone of voice and
interacting properly with another
human being).

40. COGNITIVE ABILITY
LEFT BRAIN RIGHT BRAIN
GENERAL
INTELLIGENCE
ROTE MEMORY/
REPETITION
VERBAL REASONING SPATIAL ABILITY
understand the spatial
relations among objects
PSYCHOMOTER
ABILITY
physical
movement
NUMERICAL ABILITY

41. COGNITIVE ABILITIES
Cognitive Ability/Brain Function Skills involved
Perception
Recognition and interpretation of sensory stimuli
(smell, touch, hearing, etc.)
Brain challenges: Is this a circle?
Attention
Ability to sustain concentration on a particular
object, action, or thought.
Ability to manage competing demands in our
environment. Brain challenges:
 Spot the differences
Memory
Short-term/ working memory (limited
storage).
Long-term memory (unlimited storage).
Brain challenges: games to test memory

42. Cognitive Ability/Brain Function Skills involved
Motor
Ability to mobilize our muscles and bodies.
Ability to manipulate objects.
Brain challenges:
Tap your right hand on the table. At the same
time, make a circular movement with your left
hand (as if you were cleaning the table)
,Switch hands
Language
Skills allowing us to translate sounds into
words and generate verbal output.
Brain challenges: what word & its assocition
Visual and Spatial Processing
Ability to process incoming visual stimuli.
Ability to understand spatial relationship
between objects .Ability to visualize images
and scenarios.
Brain challenges:
 Build the box
 Which piece is missing?

43. Cognitive Ability/Brain Function Skills involved
Executive Functions
Abilities that enable goal-oriented behavior, such as the
ability to plan, and execute a goal. These include:
Flexibility: the capacity for quickly switching to the
appropriate mental mode.
Theory of mind: insight into other people’s inner
world, their plans, their likes and dislikes.
Anticipation: prediction based on pattern recognition.
Problemsolving: defining the problem in the right way
to then generate solutions and pick the right one.
Decision making: the ability to make decisions based
on problem-solving, on incomplete information and on
emotions .
Emotional self-regulation: the ability to identify and
manage one’s own emotions for good performance.
Sequencing: the ability to break down complex actions
into manageable units and prioritize them in the right
order.
Inhibition: the ability to withstand distraction, and
internal urges.
Brain challenges:
 Sunday afternoon quiz?
 Which way is the bus going?

44. • With continued distress at the workplace,
workers will develop psychological and
physiological dysfunctions and decreased
motivation in excelling in their position.
44

45. RELATED DISODERS
• Stress-related disorders encompass a broad array
of conditions, including psychological disorders
like depression, anxiety, trauma disorders ) and
other types of emotional strain ( dissatisfaction
,fatigue , tension, etc.).
• maladaptive behaviors (aggression , substance
abuse), and
• cognitive impairment (e.g., concentration and
memory problems)
45

46. Compatibility
• It refers to degree to which relationships are
consistent with human expectations
• It provides
 Learning is faster.
 Reaction time is faster.
 Fewer errors are made.
 User satisfaction is higher.
46

47. Types of Compatibility
• Conceptual compatibility
• Movement compatibility
• Spatial compatibility
• Modality compatibility.

48. CONCEPTUAL COMPATIBILITY
• deals with the degree to which codes and
symbols correspond to the conceptual
associations people have.
• In essence, conceptual compatibility relates to
how meaningful the codes and symbols are to
people who must use them.
• An aircraft symbol used to denote an airport
on a map would have greater conceptual
compatibility than would a green square.

49. MOVEMENT COMPATIBILITY
• Relates to the relationship between the
movement of displays and controls and the
response of the system being displayed or
controlled.
• Example of movement compatibility is
where clockwise rotation of a knob is
associated with an increase in the system
parameter being controlled.

50. SPATIAL COMPATIBILITY
• Refers to the physical arrangement in space
of controls and their associated displays.
• For example, imagine five displays lined up in
a horizontal row.
• Good spatial compatibility achieved by
arranging the control knobs associated with
those displays in a horizontal row directly
below the corresponding displays.

51. Spatial compatibility
It deals with
• Physical similarities between displays and
their controls.
• Arrangement of displays and their control.
51

52. An example
52

53. • Function keys arranged on keyboard in two
basic configurations
• Either as row across the top of keyboard or in
columns on one side.
• Some programs present labels for function
keys on the screen. The labels can then be
changed as the meaning of key changes.
53

54. • Bayerl, Millen and Lewis compared
configurations for presenting function key
labels on the screen when keyboard with
different function key arrangements.
• When the labels are arranged in a manner
physically similar to the arrangement of the
key on the keyboard response time is much
faster.
54

55. Physical arrangement of displays and
control
• For optimum use corresponding displays and
control should be arranged in corresponding
patterns.
• This aspect of study can be done by
investigating the arrangement of burner
controls on a four burner stove.
55

56. 56

57. • Chapanis and Lindenbaum and Ray and Ray
presented various arrangements of burner
and control.
• They asked their subjects to turn on specific
burners. Errors are noted.
• Taking both studies together arrangement 1
was clearly best.
57

58. Modality Compatibility
• Refers to the fact that certain stimulus-response
modality combinations are more compatible with
some tasks than with others.
• Example: responding to a verbal command that
needs verbal action is faster than responding to a
written or displayed command requiring the
same verbal action.

60. INFORMATION THEORY
• Information theory defines information as the
reduction of uncertainty.
• The occurrences of highly certain events do
not convey much information since they only
confirm what was expected.
• The occurrences of highly unlikely events,
however convey more information

61. UNITS OF MEASURE OF INFORMATION
• Information theory measures information in bits
(symbolized by H).
• A bit is the amount of information required to
decide between two equally likely alternatives.
• When the probabilities of the various alternatives
are equal, the amount of information H in bits is
equal to the logarithm, to the base 2, of the
number N of such alternatives, or
H = LOG2 N

62. • When the alternatives are not equally likely,
the information conveyed by an event is
determined by the following formula:
hi= log2( 1 / Pi)
• where hi is the information (in bits)
associated with event i, and Pi is the
probability of occurrence of that event.
• The average information Hav is computed as
follows: Hav = ∑Pi (log2 1/ Pi= 1)
• Percentage of redundancy is usually computed
from the following formula:
% Redundancy = (I – Hav/Hmax)

63. INFORMATION PROCESSING MODEL
• A model is an abstract representation of a
system or process.
• The criterion for evaluating a model is utility.
• Good model is one that can account for the
behavior of the actual system or process and
can be used to generate testable hypotheses
that are ultimately supported by the behavior of
the actual system or process.
• Models can be mathematical, physical,
structural, or verbal.
• Information theory and signal detection theory -
MATHEMATICAL MODEL OF INFORMATION

64. DISPLAYING INFORMATIONS
• Information from original sources comes to us :
1) directly
2) indirectly
• Indirect stimuli are of 2 types:
1. coded stimuli, such as visual or auditory
displays.
2. Second, they may be reproduced stimuli, such
as those presented by
TV, radio, or photographs or through such devices
as microscopes, binoculars, and hearing aids.

65. Types of information presented by
displays
• Information is divided as Dynamic or Static.
• Dynamic information continually changes or is
subject to change through time.
• Examples include traffic lights that change from
red to green, speedometers, radar displays, and
temperature gauges.
• With the advent of Computer displays or visual
display terminals (VDTs), the distinction between
static and dynamic information is becoming
blurred.

66. CODING OF INFORMATION
 Coding takes place when the original stimulus
information is converted to a new form and
displayed symbolically.
 Examples include radar screens that display
aircraft as blips,
 maps that display population information
about cities by using different-sized letters to
spell the names of cities,

67. • When information is coded, it is coded
along various dimensions.
• For example, targets on a computer screen
can be coded by varying size, brightness,
color, shape, etc.

68. Characteristics of a Good Coding
System
Detectability of Codes
 It has to be able to be detected by the human
sensory mechanisms under the environmental
conditions anticipated.
 Color-coded control knobs on underground
mining equipment, for example, would likely
not be detectable in the low levels of
illumination in underground mines.

69. • Discriminability of Codes:
• Every code symbol, even though detectable, must
be -discriminable from other code symbols.
• If different size are used to code information,
people will confuse one for another and hence
fail to discriminate among them.
• Meaningfulness of Codes : A coding system
should use codes meaningful to the user.
• Meaning can be inherent in the code, such as a
bent arrow on a traffic
• Meaning can be learned, such as using red to
denote danger.

70.  Standardization of Codes :
• It is important that the codes be standardized and
kept the same from situation to situation.
• If new display is to be added to a factory already
containing other displays, the coding system used
should duplicate the existing coding schemes.
• Red, for example, should mean the same thing on
all displays.

71. PERCEPTION
• The most basic form of perception is simple
detection
• Even the act of simple detection involves
some complex information processing and
decision making.
• This complexity is embodied in signal
detection theory.

72. MEMORY
• The human memory system has been divided
as three subsystems or processes: sensory
storage, working memory, and long-term
memory.
• Working memory is the gateway to long-term
memory.
• Information in the sensory memory subsystem
must pass through working memory in order
to enter long term memory.
• Human memory is vast, but imperfect. We
possess trouble to remember.

73. TWO KINDS OF MEMORY
1. SHORT TERM MEMORY
2. LONG TERM MEMORY

74. SHORT TERM MEMORY(STM)
• A temporary store or buffer in which small
amount of informations are retained while
particular mental or physical operation is
carried out.
• For ex: remembering a phone number while
writing down.
• It contains symbols related to current
processing but has limited storage capacity.
• Its storage limitations can cause errors

75. • For ex: 1) forgetting important data before it
can be consolidated in long term memory or
acted during a sequence of operations.
2) forgetting of intermediate results when
doing mental arithematic or omitting one of
ingredients of a recipe.
• It is referred to as working memory

76. LONG TERM MEMORY(LTM)
• It contains symbolic structures built up through
learning in which new data can be embedded.
• General knowledge of world and of life events is
stored in LTM.
• It is more or less permanent
• It is associative in nature: data can be
represented in context of past behavior, but
takes time.

77. WORKING MEMORY
RELATION BETWEEN LTM, WORKING
MEMORY, MEMORY OPERATIONS
MENTAL
OPERATIONS
SENSORY
CODES
LTM

78. DECISION MAKING
• Decision making is really at the heart of information
processing.
• A number of biases are inherent in the way people seek
information, estimate probabilities, and attach values to
outcomes that produce this irrational behavior.
• The following is a short list of some of these biases:
• People give an undue amount of weight to early evidence
or information.
• Subsequent information is considered less important.

79. ATTENTION

80. Attention in Middle Childhood
Attention becomes
more:
• Selective
• Adaptable
• Planful

81. ATTENTION
• It is activity directed to facilitate processing of
an expected stimulus.
• In Wicken’s model it is presented as a limited
resource that is channeled to ‘drive’ processes
such as working memory, response execution
etc.
• It is like a spotlight that illuminates the
information world or to use as computer
analogy as CPU responsible for scheduling tasks
and allocating them to subroutines.

82. How many tasks we can do
simultaneously ?
• The number of inputs an operator can attend at
once and how many operations can be carried
out simultaneously.
• This is important if information overloading is to
be avoided
• Humans are multimodal is in sense of being able
to process and represent information in many
modalities(visual, auditory, semantic)and many
activities( walking, standing) can be carried out
without being consciously attended.

83. Should people be allowed to use
cellphones while driving ?

84. MACHINE COMPONENTS
A “Machine” can be any man-made device
that augments work capacity.
Components:-
The Controlled Process
Displays
Controls
The Immediate Environment
Workspace
The Physical Environment
Work Organization

85. The Controlled Process
The basic operation of the machine on its
local environment controlled by the humans.
Example:-
Digging a vegetable garden with a spade.

86. Displays
Displays are the action of the machine on
its local environment.
Example:-
Driving a motor car –Display comes from
controlled processes(view of the road) and from
gauges, dials etc.
If there is no access to controlled processes,
then interaction with machine is by artificial
displays.

87. Controls
Human interaction with machines depends
on the provision of suitable controls, which are
acted on by the effectors.
Example:-
Steering of car, handle of an axe etc.

88. SUMMARY
Ergonomics –the only scientific subject that
focuses specifically on the interaction between
people and machines.
Provides standardized approach to the analysis
of workplace.
Ergonomics is a multidisciplinary subject.