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Chapter 8

Psychology 2990A/B Chapter Notes - Chapter 8: Engineering Psychology, National Transportation Safety Board, Pilot Error


Department
Psychology
Course Code
PSYCH 2990A/B
Professor
Doug Hazlewood
Chapter
8

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Chapter 8: Engineering Psychology
The Development of Engineering Psychology
Machines/tools/equipment must be compatible with the workers that use them
Pairing operator and machine is the province of engineering psychology (also called human
factors or human engineering)
oBritish psychologists use term ergonomics (ergon- work, nomos- natural laws)
Engineering psychology is the science of designing/engineering machines and equipment for
human use and of engineering human behaviour for the efficient operation of the machines
Until 19402, engineers solely responsible for designing machines based on
electrical/mechanical ect and didn't pay attention to workers who use them
Machine considered constant factor and humans had to adapt to them
Adapting worker to machine accomplished through time-motion study: jobs were analyzed
to determine how they could be simplified
oThis approach ignored operators needs and couldn't be maintained
Impetus of Military Needs
Weapons for WW2 placed greater demands on human abilities -sensing, perceiving, strength
Wartime equipment worked well but mistakes were frequent (most precise bombsight didn't
lead to accurate bombing)
Although machinery seemed to be operating correctly, system of interaction between
operator and machine was not
Engineering psychology developed from this wartime need
Early example helped pilots by making the cockpit controls consistent in different models so
that pilots who adapted to one model doesn't go to another model and push the wrong
buttons and get confused where things are
1979: Accident at nuclear plant 3 Mile Island (Pennsylvania) because lacking consideration
for human need, the dials that controlled nuclear reading were too far apart so if reading was
too high valuable time was lost running from one dial to the other to fix problem (they had
to modified control rooms to consider abilities and limitations of human operators)
Human factor in aircraft accidents: 66% is pilot error – so National Transportation Safety
Board added engineering psychologists to its staff (investigate pilot/crew fatigue, schedules,
health issues, stress, equipment design ect)
Most human factors research done on passenger cars to make them safer
Since 1985 every passenger car must have break light in rear window as a result of human
factors research on 8000 vehicles in which it reduced rear-end collisions by 50%
oHuman factors research also on how drivers perceive/comprehend risky situations
and make decisions about responding
Research also done on the effect of tinted car windows on visibility which showed detection
of objects/pedestrians while backing up is reduced when windows are tinted
oOlder drivers more effected by tinted windows than younger drivers (60-69 greater
reduction in contrast sensitivity to light than did age 20-29)
Design for Ergonomic Needs
Engineering psychologists contribute to design of many other things
oContributed to redesign of mailbags because more than 20% of letter carriers report
musculoskeletal problems from carrying over the shoulder mailbags (now use waist
support strap and double bag that requires both shoulders)

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Most well developed programs are in automobile, electronics and food industries, as well as
in the design of workstations for a variety of businesses (GM, Daimler Benz, SAAB, Volvo,
IBM)
Economic benefits of applying ergonomic research showed net gains of 1%-12% over the
cost of the human factors intervention (usually within less than 1 year)
Rear break lights initially cost industry $10 per car and return is 434 million in lower repair
costs
Field of engineering psychology is hybrid and practitioners have diverse backgrounds
(membership of Human Factors and Ergonomics Society consists primarily of engineers and
psychologists but also medical, sociology, anthropology computer science, behavioural and
physical professionals)
Big increase in number of masters level psychologists undertaking engineering psychology
Time and Motion Study
Time-and-Motion Study – early attempt to redesign work tools and equipment and to
reshape the way workers perform their jobs from 3 pioneers focusing on ways to make
physical labour more efficient
Frederick W. Taylor (1898): first attempt to study performance on specific job tasks by
investigation the nature of shovelling for large U.S. street manufacturer
oFocused on tool design and incentive wage systems
oTaylor saw they were all using different sized shovels that lifted different size loads
(3.5-38 pounds) and by experimenting determined optimum shovel where workers
were most efficient held 21.5 pounds
oHe also introduced different sized shovels for different materials and saving the
company $78000+ a year (now 140 men could do work that would take 500 before)
and by offering higher pay incentive for greater productivity, they allowed workers
to increase their wages by 60%
Frank Gilbreth (engineer) Lillian Gilbreth (psychologist) – pioneers who did more than
anyone else to promote the time-and-motion study
oFocused on the mechanics of job performance, to eliminate all unnecessary motion
oFrank at 17 was bricklayer and noticed unnecessary motions and came up with
method that made him the fastest and told others which increased efficiency by
changing to only the efficient hand/arm movements he analyzed as most efficient in
bricklaying – resulting in 350 bricks/worker/hour instead of 120
Didn't force men to work faster, just reduced motion from 18 to 4.5 per brick
oFrank also buttoned shirt from bottom up (4 sec saved), used 2 brushes to put
shaving cream on face (17 sec saved)
oEfforts to schedule activities for their 12 children were recounted in Cheaper by the
Dozen book/movie
Time-and motion engineers (sometimes called efficiency experts) have applied these
techniques to many types of jobs (e.g. dental assistant passes tool to dentist reducing
motions which reduces operating time)
Drivers carry packages only in left arm, step out on right food, walk 3 feet/second, and hold
trucks keys with teeth face up
Most significant results of time-and-motion study is with routine/repetitive work
Typical motion study: workers movements recorded on video and analyzed to modify or
eliminate wasteful motions (also applied by sports psychologist/coaches)
Guidelines for Efficient Work

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Rules for increasing the ease, speed, and accuracy of manual jobs:
1. Minimize distance workers must reach to get tools/supplies or to operate machines
2. Both hands should be as symmetrical as possible (begin/end, reach right while left)
3. Hands should never be idle except during rest breaks
4. Hands should never do tasks that can be performed by other body parts (legs, feet)
5. When possible, work materials should be held by mechanical device (eg vise) not hand
6. Workbench/workheight should be of sufficient height that job can be performed while
standing or sitting on a high stool (alternative positions relieve fatigue)
While companies reap greater outputs and employees jobs are made easier by these
guidelines, worker/labour unions have been suspicious and argued only reason for time-and-
motion study is to force employees to work faster (leads to lower pay and dismissals
because less workers needed, and also leads to boredom, lack of challenge, low motivation)
Time-and-motion analysis most applicable today for routine tasks (assembly line jobs)
Complex operations/equipment/functions require total relationship between person and
machine be considered, and more sophisticated person-machine interaction approach needed
Person-Machine Systems
Person-Machine System – system in which both components work together to accomplish a
task and neither part is of value without the other (eg. person pushing lawnmower)
In all person-machine systems: human operator receives input on status of machine from
displays, and operator regulates equipment by using controls to initiate some action
System: display – sensing – human info processing – controlling – controls – machine info
processing – display
oExternal info also received which person processes then dictates change to machine
It's the total system that is the starting point for the engineering psychologists job
Person-machine systems vary in the extent to which human operator is actively and
continuously involved
oWhile some automated equipment can operate itself they cannot design, build, or
maintain themselves so humans remain important parts of such manufacturing
systems even when they’re not directly/continuously operating the equipment
Employees prefer to operate the equipment over monitoring automated equipment making
engineering psychologists job harder and requires monitoring equipment designed to keep
observers alert/vigilant
Definition/requirements of person-machine systems are the same regardless of degree of
involvement of worker with the machine
Allocating Functions
First step in design of person-machine system is making decisions about division of labour
oEach step/process in functioning of total system must be analyzed to determine its
characteristics: the speed, accuracy, and frequency with which its performed and
stress under which it occurs
Then engineering psychologists can match requirements of system with abilities of person
and of machine (both people and machines have advatages and limitations)
Machines are better than humans in performing the following functions:
oCan detect stimuli (radar wavelengths, ultraviolet light) beyond human sensory
capacities
oCan monitor reliably for lengthy periods as logn as stimulus in question is
programmed or specified in advance for the machine
oCan make large number of rapid, accurate calculations
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