Ergonomics
User interfaces
Jaana Holvikivi 2014
The Discipline of Ergonomics
Ergonomics (or human factors) is
 the scientific discipline concerned with the
understanding of interactions among humans
and other elements of a system, and
 the profession that applies theory, principles,
data and methods to design in order to optimize
human well-being and overall system
performance.
International Ergonomics Association:
http://iea.cc/01_what/What%20is%20Ergonomics.html
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Helsinki Metropolia University of Applied Sciences
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Ergonomics
 Derived from the Greek
ergon (work) and
nomos (laws)
to denote the science of work,
 ergonomics is a systems-oriented discipline
 ergonomics promotes a holistic approach in
which considerations of physical, cognitive,
social, organizational, environmental and other
relevant factors are taken into account
14.11.2010
Helsinki Metropolia University of Applied Sciences
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Human-machine systems
Ergonomics is the study of the interaction between
people and machines.
Systems can be improved by:
 designing the user interface to make it more
compatible with the task and the user
 changing the work environment to make it safer
and more appropriate to the task
 changing the task to make it more compatible
with user characteristics
 changing the way work is organized to
accommodate people’s psychological and social
needs
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Helsinki Metropolia University of Applied Sciences
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Domains of specialization
 Physical ergonomics
is concerned with human anatomical,
anthropometric, physiological and biomechanical
characteristics as they relate to physical activity.
Relevant topics include
 working postures,
 materials handling,
 repetitive movements,
 work related musculoskeletal disorders,
 workplace layout,
 safety and
 health.
14.11.2010
Helsinki Metropolia University of Applied Sciences
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Domains of specialization
 Cognitive ergonomics is concerned with
mental processes, such as perception, memory,
reasoning, and motor response, as they affect
interactions among elements of a system.
(Relevant topics include mental workload, decision -making,
skilled performance, human-computer interaction, human
reliability, work stress and training.)
 Organizational ergonomics is concerned with
the optimization of sociotechnical systems,
including their organizational structures, policies,
and processes.
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Helsinki Metropolia University of Applied Sciences
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General ergonomics checklist
1. Job analysis
2. Work organization
3. Workspace design
4. Physical demands
5. Mental demands
6. Human-machine interaction
7. Work environment
8. Workforce characteristics
9. Job stress
10.Occupational background
(abbreviated from Bridger, p. 21-25)
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Helsinki Metropolia University of Applied Sciences
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General principles for control – display
integration
Principle
Description
Importance
Most important items must be in the most
advantageous positions
Frequency of use
Most frequently used items must be in the
most advantageous positions
Function
Use grouping principles to group items by
function
Location compability
Locate control near their corresponding
displays
Conceptual compability
Layout and use of controls should be
consistent with user/ popular stereotype
Sequence in real tasks
Use link analysis to optimize layout in relation
to the sequence of movements
Effort balance
Share workload between dominant and
nondominant hands
14.11.2010
Helsinki Metropolia University of Applied Sciences
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Mental workload
Consequences of mental strain (ISO 10075)
 Warming-up effect
 Mental fatigue, fatigue-like states:
 monotony,
 lack of vigilance,
 mental satiation (strong rejection)
14.11.2010
Helsinki Metropolia University of Applied Sciences
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Factors affecting mental workload
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(Bridger p. 482)
ambiguity of the goal
competing goals
unclear serving strategy (priorities)
task complexity (too low, too high)
adequacy of information
signal discriminability
redundancy
parallel versus serial processing
time-sharing (switching attention between tasks)
14.11.2010
Helsinki Metropolia University of Applied Sciences
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Factors affecting mental workload
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(cont.)
delays in system response
mental models
recognition vs recall
controllability
error tolerance
environmental design
social interaction
time pressure
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Helsinki Metropolia University of Applied Sciences
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Some characteristics of poor performance
resulting from excessive work demands (p. 484)
 slower reaction time
 increased time to
complete task
 increased forgetfulness
 inability to concentrate
 lapses of attention
 missing or misinterpreting
signals
 omitting steps in a
procedure
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 increased need for
instruction
 narrowing of attention
 erratic operation of
controls
 mistiming of actions
 making unnecessary
responses
 carrying out irrelevant
tasks
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General principles of software
ergonomics
Appropriate software
1. is suitable to the task
2. is easy to use and adaptable
3. provides feedback on system performance
4. works at the user’s own pace
5. does not “spy” on the user.
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1. Software is suitable to the task
 it presents users with no unnecessary
obstacles or problems
 is not necessarily complex or elaborate
 supports the user in the effective and efficient
completions of the task
 present the user only with the information
related to the completion of the task while the
task is being carried out
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Helsinki Metropolia University of Applied Sciences
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2. Software is easy to use and adaptable
 is easy to master
 input and output formats are appropriate to the
task requirements and user goals
 actions that can be allocated to the interface
software are carried out automatically without
user involvement (e.g. default values)
 uses dialogue appropriate to the user’s ability
 has an interface adaptable to different skill
levels
 minimizes consequences of error: lost data are
recoverable & “undo button”
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Helsinki Metropolia University of Applied Sciences
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3. Software provides feedback on system
performance
 timely error messages
 appropriate level of information
 task dependent help on request
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Helsinki Metropolia University of Applied Sciences
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4. Software works at the user’s own pace
 user “drives” the system
 system displays all keystrokes when they are
made
 system response time and response time
variability is minimized
 during performance of a task in which data are
changed, the original data remain accessible
until no longer required by the tasks
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Helsinki Metropolia University of Applied Sciences
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5. Software does not “spy” on the user
 no covert monitoring of user performance
 users are informed of any recording of their
input
 emphasis on quality rather than quantity
14.11.2010
Helsinki Metropolia University of Applied Sciences
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Computer hassles
By RA Hudiburg, 1998
Test your computing stress:
 Listed below are a number of ways in which a
person can feel hassled by computers and
computer technology. Respond to each hassle
by circling a 0, 1, 2, or 3 to indicate how
SEVERE the hassle has been for you during the
past TWO MONTHS.
 SEVERITY:
 0 - not at all ; 1 - somewhat severe; 2 - moderately
severe ; 3 - extremely severe
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HASSLES
1. computer system is down
2. lost in the computer
3. poorly documented software
4. computer hardware failure
5. computer keyboard lockup
6. programming error
7. illegal input message
8. updated software requirements
9. poor user/computer interface
10. slow program speed
11. slow computer speed
12. poorly written computer
documentation
13. incompatible software program
14. incomprehensible computer
instructions
15. outdated computer skills
16. increased time demands
17. electrical surges - data are lost
18. lost data
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lost program
crashed program
crashed system/ lockup
damaged storage media - disks, tapes
need to update skills
keyboard typing errors
need to learn new software
forgot to save work
keyboard paralysis
uninformative computer conversations
violent language of computers
too much computer information
too little computer information
software confusion
lack of help with a computer problem
lack of computer expertise
increased computer use expectations
lack of computer application software
obsolete computers
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