Matakuliah : L0064 / Psikologi Industri &
Organisasi 1
Tahun
: 2007 / 2008
PSIKOLOGI REKAYASA
Pertemuan 21
Learning Objectives
After reading this chapter, students should be able to:
1. Define ergonomics and describe its role and function in the
workplace
2. Outline the history and scope of engineering psychology
3. Explain the relationship of displays, controls, and the human
operator in a person-machine system
4. Describe the major considerations involved in the design of a
workspace
5. Contrast the advantages and disadvantages of auditory and
visual presentation of information
6. Define telematics and its importance to engineering psychology
7. Describe the use of human factors in everyday life, with
examples
8. Understand and explain the factors that should be considered in
the design of a computer work station
What is Engineering Psychology?
• The design of machines and equipment for human use,
and the determination of the appropriate human
behaviors for the efficient operation of the machines
• Also called
– Human factors
– Human engineering
– Ergonomics
History and Scope of Engineering
Psychology
• Prior to 1940, engineers made machines without
considering the human factor
• The worker was adapted to the machine through
time-and-motion studies
• WW II weaponry was complex but did not perform
up to expectations, thus giving rise to engineering
psychology
– Example: There was no consistency in design of
aircraft controls. “On” position for some controls was
up, for others, down – difficult to remember in a dog
fight. Many pilots died as a result
History and Scope of Engineering
Psychology
• Poor design resulted in many accidents
– Three Mile Island in 1979 - poor design of controls
• NTSB added engineering psychologists to its
staff to study pilot error
• Human factors research resulted in safer
automobiles, including redesigns of headlights,
brake lights, and tinted windows
• Other areas of effort include license plate
visibility, signage, cell phone use while driving,
driver aggression, and mailbag design
• Ergonomics has net gains of 1 to 12% over the
costs of human factors interventions
Engineering Psychology is a Hybrid
• Members of the Human Factors and Ergonomics
Society includes:
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Psychologists
Engineers
Medicine
Sociology
Anthropology
Computer sciences
Other behavioral and physical sciences
Time and Motion Study
• An early attempt to redesign work tools and to
reshape the way workers performed routine,
repetitive jobs
• F.W. Taylor (1898) performed first empirical
demonstration of the relationship between work
tools and worker efficiency
– Introduced shovels of different sizes for handling
different materials
• 21 1/2 pounds was the most efficient load at a U.S. Steel
company study
– Saved the company $78,000 per year
Time and Motion Study
• Frank and Lillian Gilbreth (1911) were interested
in the mechanics of job performance to
eliminate unnecessary motion
– Started with improving the efficiency of bricklaying
– Increased rate of bricklaying from 120 to 350 bricks
an hour by reducing motions from 18 to 5
• The basic unit of motion was the Therblig
(Gilbreth spelled backwards)
• Gilbreth’s had 12 children – their lives were
depicted in the movie Cheaper by the Dozen
• More info at http://gilbrethnetwork.tripod.com
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Guidelines for Increasing Efficiency of
Manual Jobs
Minimize reaching distance from worker
Symmetrical movements of both hands
Hands should never be idle
Hands never do tasks that can be performed by other
parts of body
• Work materials held by a vice
• Workbench height adjusted to prevent fatigue
Person-Machine System
• A system in which human and mechanical components
operate together to accomplish a task
• Human operator receives input on machine status from the
displays
• Such systems vary in the extent to which the human
operator is actively and continuously involved
• Humans remain important components of automated
manufacturing systems
• Automation makes the engineering psychologists job more
demanding as monitoring machinery is more monotonous
than actually operating it
Allocating Functions Between The
Operator & Machine
• Engineers first carefully analyze each process in the
functioning of the total system to determine its
characteristics
– Speed, accuracy and frequency with which it is performed
– Stress under which occurs
• They then make decisions regarding man - machine
division of labor
Machine Strengths
• Detecting stimuli beyond human sensory
capacities
• Monitoring reliably for lengthy periods
• Making large numbers of rapid, accurate
calculations
• Storing and retrieving vast amounts of
information
• Applying continuous and rapid physical force
• Engaging in repetitive activities
Machine Limitations
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Not very flexible
Cannot learn from errors
Cannot improvise
When operators only monitor, disastrous results can
happen
– e.g., bored pilots or subway drivers
• However, full automation is dangerous as systems can
fail – no intervention available without human monitor
Principles for Workspace Design
• All materials should be placed in order in which they will
be used so paths of movements will be continuous
• Tools should be pre-positioned for use
• All parts and tools should be within comfortable reach
– Greater than about 28 inches causes unnecessary repositioning
and consequent loss of efficiency and increased fatigue
Other Design Considerations
• Heights of all working surfaces should be adjustable
• Hand tools should be designed for use without bending
wrists
– Hammers with angled handles work better
• Properly designed tools affect productivity, satisfaction,
and physical health
– e.g., reduction of carpal tunnel syndrome
Human Anthropometry
• A branch of engineering psychology concerned with
measurements of the physical structure of the body,
including
– Height – standing and sitting
– Shoulder breadth
– Back height
– Chest depth
– Foot and hand length
– Knee angle
• These measurements are applied to design of work areas
to determine normal and maximum reaching distances,
tool and desk height and arrangement, etc.
Presenting Visual Information in Displays
• Visual presentation is most appropriate when
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Message is long, difficult and abstract
Environment is too noisy for auditory signals
Auditory channels are overloaded
Multiple kinds of information to be presented simultaneously
Auditory Presentation of Information
• Auditory presentation most effective when:
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Information is short, simple, and straightforward
Message is urgent
Environment is too dark for visuals
The operator’s job requires moving to different locations
Types of Visual Displays
• Quantitative displays present a precise
numerical value such as speed, altitude or
temperature
• An open window display is read with fewest
errors, and the vertical display was misread one
third of the time (See Fig. 13-5)
• Digital display can be read faster with fewer
errors, but cannot be used in all situations
– e.g., if conditions are rapidly changing, or need to know direction of
change
Qualitative Displays
• Displays that present a range rather than a precise
numerical value
– e.g., red area hot – green area normal – yellow area cold
• Consistent patterning makes multiple displays easier to
read
– Used in aircraft cockpits
• Unpatterned displays force operator to read each dial
separately
Check Reading Visual Displays
• Simplest kind of visual display
• Tells operator whether the system is:
– On or off
– Safe or unsafe
– Normal or abnormal
• Warning light most common
– Twice as bright as background
– Centered in field of vision
– Flashing
Auditory Displays
• Auditory displays can be more compelling than visual
because
– Ears always open
– Multi-directional
– Visual often taxed to capacity
• Problem with “nuisance alarms”
– If alarms are too sensitive or occur too frequently, they are often
ignored
Guidelines For Controls
• Control-body matching
– Most rely on hands and feet
– No one limb should be given too many tasks
• Control-task compatibility
– A control action should imitate the movements it
produces
– Turning steering wheel right makes right turn
• When possible, combining controls that perform
similar or related functions is more efficient
Guidelines For Controls
• Identification of controls
– Controls should be clearly marked or coded
• e.g., shape coding for touch recognition
• Placement of controls
– Consistency and uniformity is important
– Consider cultural influences on preferences
– Emergency controls in line of sight, clearly distinguishable and
protected with a cover
– Group related controls and displays according to function
Human Factors in Everyday Life
• Human factors no longer confined to tanks,
airplanes and work areas
– Telematics deals with wireless information
technology such as GPS, Satellite radio, and builtin wireless phone for cars
– Ergonomics examines cell phone use while driving
to prevent accidents
– Use of auditory signals to alert drivers they are too
close to another car
– Spatulas that reduce risk of carpal tunnel,
sharpened ice cream scoops….
Computers
• Poorly designed computers and work stations
produce strain and discomfort
– Eyestrain and blurred vision
– Fatigue and pain
• Comfort range for keyboard operation is an
angle of 7-20 degrees with an elbow angle of 90
degrees
• Optimal viewing distance of 15 to 30 inches
• Optimal screen height is 33-42 inches
• Mouse redesigned to reduce movements
Key Terms
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Auditory displays
Check reading visual displays
Engineering psychology
Human anthropology
Person-machine systems
Qualitative visual displays
Quantitative visual displays
Shape coding
Time-and-motion study