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Cognitive ergonomics – interaction between
human and system that considers the human
abilities and limitations
application and psychology to work
Perception – based on how we interpret all
these different sensations
Three (3) Perception Process:
1. Selection – is your decision on what you
want to focus to
2. Organization – choosing on what kind
of reaction we are going to make
depending on the situation.
3. Interpretation – categorizing the effects
from the first two stages.
VISUAL DISPLAYS – device with a screen that
displays characters
Visual - something that appeals to the sight
Display - to put / spread before the view; a
public showing of objects of interest.
Factors influencing visual display effectiveness
A. Physical location
1. positioning of a visual
2. Location of a display
3. the size of the informational content
and the time course of the signal.
B. Display Arrangements
C. Lighting Conditions
D. Static versus dynamic displays
E. Display coding
2. Color and Contrast – There are actually
two color systems: one which deals
with emitted light and one which deals
with reflected light.
colors of light that we perceive can be
produced by combinations of the three
primary colors: Red, Green, and Blue
Subtractive Color - pertains to an
illuminated object that reflect lights, but
does not produce its own
Additive Color - pertains to self-luminous
light sources
3. CIE (Color Matching) – the Commission
Internationale de l’Eclairage (CIE)
developed a light measurement
4. Color displays –more appealing to the
eye than monochrome displays
*Color Coding – help us see patterns
and distinguish one area from another
5. Pre-attentive Processing (Parallel
Processing and Pattern Recognition)
6. Text & Character Attributes
• Contrast - Brightness contrast
between character and background.
• Size - Height, height-to-width ratio,
strokewidth-to-height ratio, character
spacing, word/item spacing, and line
• Font - Character shape, presence or
absence of serifs.
• Color - Choices for text, background,
Selecting the appropriate character and text
attributes depends on:
1. Human visual system – is sensitive only
to a small portion of the
electromagnetic spectrum
• User Population - Who will use the
• Display Application - How will the
display be used
• Environment - Will the display be
used in an office environment, an air
traffic control tower, aircraft cockpit,
maintenance area, or equipment
7. Symbols and Icons –
• Icon - identified without text or
• Symbol - no physical resemblance to
what it represents. Its meaning must be
• Computer Icon - usually placed within
a border that may or may not contain a
Auditory Presentation
Avoid extreme auditory dimensions - if sound is
too loud or there will be a "startle response".
βœ“ Signal/noise ratio - establish intensity relative
to ambient noise levels to avoid masking.
βœ“ Variable Signal - works best to attract
attention by minimizing perceptual adaptation
to monotones and increasing the delectability
of the signal, e.g. Beep! Beep! Beep! is better
than "Beeeeeeep"!
βœ“ Don’t overload the auditory channel –
consider the effect of the auditory information
on the whole system
–used to orient attention to events outside the
user's field of view
Warning Signals - Auditory displays are useful
for signaling alarms
General Principles
1. Compatibility - Make use of pre-existing
stimulus-response relationships
2. Orienting reflex - is a basic reflex to turn to
the source of a sound (stimulus),
3. Learned - Examples are sirens which are
learned to be associated with an emergency.
4. Approximation - Complex messages should
be presented in two stage signals:
a. Attention Demanding Signal - to
capture attention.
b. Designation Signal - with precise
message information.
5. Dissociability - Auditory signal must be
discernible from other noise, e.g. when several
phones ring in an office it's difficult to tell which
is ringing.
6. Parsimony – short message
7. Invariance - to avoid confusion
Auditory Processing – how the brain perceives
and interprets sound information
Step 1: Auditory Awareness
a) Auditory Awareness - the ability to detect
b) Sound Localization - the ability to locate the
sound source
c) Auditory Attention/Auditory Figure-Ground the ability to attend to important auditory
information including attending in the midst of
competing background noise.
Step 2: Auditory Discrimination
a) Auditory Discrimination of Environmental
Sounds - the ability to detect differences
between sounds in the environment
b) Auditory Discrimination of Suprasegmentals
- the ability to detect differences in nonphoneme aspects of speech including rate,
intensity, duration, pitch, and overall prosody
c) Auditory Discrimination of Segmentals - the
ability to detect differences between specific
speech sounds.
Step 3: Auditory Identification
a) Auditory Identification (Auditory
Association) - the ability to attach meaning to
sounds and speech
b) Auditory Feedback/Self-Monitoring - the
ability to change speech production based on
information you get from hearing yourself
c) Phonological Awareness (Auditory Analysis)
- the ability to identify, blend, segment, and
manipulate oral language structure
Step 4: Auditory Comprehension
a) Auditory Comprehension - the ability to
understand longer auditory messages
b) Auditory Closure - the ability to make sense
of auditory messages when a piece of auditory
information is missing; filling in the blanks
3. Relearning- assess the time saved while
learning material again.
Three (3) types of Human Memory
1. Sensory Memory- It acts through the five
senses of sight, hearing, smell, taste and touch
2. Short term Memory- temporary recall of the
information which is being processed at any
point in time, and has been referred to as “the
brains past-it note.
3. Long term Memory- Intended for storage of
information over a long period of time
Types of Long-term Memory:
1. Declarative Memory (Explicit Memory)
– memory of factual information,
general knowledge, data, and events
• Episodic Memory – memories of
personal experiences
• Semantic Memory – general factual
2. Procedural Memory (Implicit Memory)
– memory of how to perform a task
c) Auditory Memory - the ability to retain
auditory information
d) Linguistic Auditory Processing - the ability to
interpret, retain, organize, and manipulate
spoken language for higher level learning and
Memory – picked up by one or more senses
Memory is built and retrieved in three
different ways:
1. Recall- person retrieves information learned
2. Recognition- person has to only identify the
previous learned information.
Attention –focuses an individual's awareness
complex cognitive function
Types of Attention
1. Selective Attention- select from the various
factors to focus on only the one you want.
2. Sustained Attention- focus on one specific
task for a continuous amount of time without
being distracted.
3. Alternating Attention- allows you to shift
your focus of attention and move between
tasks having different cognitive requirement.
4. Divided Attention- process two or more
responses. It is often referred to as multitasking.
Mental workload –amount of cognitive work
required for a person to complete a certain task
over time
Mental –relating to the total emotional
Workload –amount of work
Measurement of Workload
1. Self-assessment measures - subjective or
self-report measures
2. Task performance measures - based upon
the assumption that the mental workload of an
operator influences system performance.
3. Physiological measures - take the
physiological responses of the operator's body
into account.
Environmental Factors and Their Applications
Physical Environment: Noise, Illumination,
Temperature, Vibration and Job Design
Noise Pollution Regulation – To assure that all
companies must maintain a proper and healthy
Physical environment – refers to the factors
that directly affects the human body
Audiometric testing – It is done by trained
technicians to detect any hearing loss
can increase or decrease the
Noise – unwanted sound
Sound –produced by vibrating objects
Four Major Properties of Noise
a) Frequency (Hz) – The number of waves
that pass a fixed place
b) Sound Pressure (dB) –The difference
between the instantaneous pressure
and the static pressure of the medium.
c) Sound Power (watt) – The rate at which
sound energy is emitted
d) Time Distribution – A measure of how
much time the matter spends in it
Illumination – act of placing light on an object
Two Types of Illumination
1. Natural Light – Light received on Earth
from the sun
2. Artificial Light –any light source that is
produced by electrical means
Daylight Can Be Divided into Two Components
a) Sunlight is light received at Earth’s surface,
directly from the sun.
b) Skylight is light from the sun received at
Earth’s surface after scattering in the
Three Classes of Illumination
𝐷 = 𝐢1/ 𝑇2 + β‹― + 𝐢𝑛/ 𝑇𝑛 ; X 100
Incandescent lamps – Produce light by heating
a filament. Incandescent lamps can operate
directly from mains electricity.
D – Dose C - Actual Exposure Time T – Allowable
Exposure Time
Discharge lamps – Produce light by an electric
discharge in a gas.
Noise Safety Formula (HLP)
Types of Hearing Protection
a) Ear Plugs – made of foam, rubber or
b) Ear Muffs – cover the whole ear and are
preferred by some people
c) Ear Caps – good for occasional use or
for people who find earplugs
NRR(Noise Reduction Rating)– is found on the
earmuff or earplug package
Solid state lamps – Produce light by the
passage of an electric current through a
The Wavelengths of The Light
The wavelength is (λ) unit (nm or nanometer) is
related to the frequency (f) unit (Hz or Hertz). 𝑐
c = 300,000 km/s or 3 x 10^8 m/s
Lighting Conditions That Can Cause Discomfort
Flicker – achieved by high frequency operation
Glare – to have too much light
Visual discomfort – can occur when your eyes
start to feel tired
Raynaud’s Phenomenon – A disorder of the
blood cells
Extreme Heat Health Effects
measure of warmth or coldness of an
Thermal Comfort – feels neither too cold nor
too warm
Environmental Factors
1. Air temperature – Temperature of the
air surrounding the body
2. Radiant Temperature – Heat that
radiates from a warm object
3. Air velocity – speed of air moving
across the employee
4. Humidity –the resulting amount of
water evaporated in the air
Relative humidity – is the ratio between the
actual amount of water vapor in the air
Personal Factors
1. Clothing Insulation – Clothing is both a
potential cause of thermal discomfort
2. Metabolic heat – Also called “Work
Rate”. The more physical work we do,
the more heat we produce
Extreme Cold Health Effects
Hypothermia – A common cold injury
associated with low body heat
Frostbite – when your skin's exposed to the
Trench foot – Long immersion of foot under the
Cold-induced of hives – Reddish and itching of
Chilblains – small and itchy swelling on the skin
Heat Stroke. The most serious heat-related
Heat Exhaustion. Often a precursor to heat
Heat Cramps. Caused by the body's depleted
salt and water levels from excessive sweating
Heat Rash. Skin irritation caused by excessive
Fainting. A sudden loss of consciousness
1. Dry bulb temperature – also known as
normal temperature is an indicator of
heat content and measure of how dry is
the air.
2. Wet Bulb Temperature – is a measure
of how much moisture is present in the
Vibration or oscillation – means quickly moving
back and forth
Two Types of Vibration
Whole body vibration (WBV) –when the body is
supported on a surface that is vibrating
Visual impairment – a decreased ability
to see, fixable by usual means, such as
Motion sickness – common problem in
people traveling by car
Hand-arm vibration – vibration transmitted to
the hand and arm during the operation of handheld power tools
White finger - is discoloration of the
Vibration magnitude – is the frequency
weighted acceleration value measured in m/s2
Vibration meter – used to measure vibration
Vibration Frequency – expressed in cycles per
second using the SI unit hertz (Hz)
Vibration Direction – The responses of the body
to motion differ according to the direction of
the motion
Vibration Duration – duration of exposure
Job design – involves systematic attempt to
organize tasks
Four Approaches to Job Design
1. The Mechanistic Job Design Approach
– stems from the scientific
management school of thought & time
and motion study
2. The Motivational Job Design Approach
– stems from the work in job
enrichment and enlargement
3. The Biological Job Design Approach –
derived from the sciences of
biomechanics, work physiology
4. The Perceptual/Motor Job Design
Approach – main contributors are the
human factors engineering guidelines
Job simplification – breaking the job into easier
Job enlargement – combines into one job with
two or more tasks
Job Rotation – practice of moving employees
between different tasks to promote experience
and variety
Job enrichment – giving workers more control
over how their job is performed (Frederick
Benefits of Job Design
1. Employee Input – Employees have the
option to vary tasks as per their
personal and social needs
2. Employee Training – Training is an
integral part of job design
3. Work / Rest Schedules – clearly
defining the number of hours an
individual has to spend in his/her job.
4. Adjustments –aligning the manpower
requirements for the same.