Ergonomics User interfaces Jaana Holvikivi 2014. The Discipline of Ergonomics Ergonomics (or human...

Ergonomics

User interfacesJaana 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

Helsinki Metropolia University of Applied Sciences 214.11.2014

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


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


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.


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.


General ergonomics checklist

1. Job analysis2. Work organization3. Workspace design4. Physical demands5. Mental demands6. Human-machine interaction7. Work environment8. Workforce characteristics9. Job stress10.Occupational background

(abbreviated from Bridger, p. 21-25)


General principles for control – display integrationPrinciple 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


Mental workload

Consequences of mental strain (ISO 10075) Warming-up effect Mental fatigue, fatigue-like states:

monotony, lack of vigilance, mental satiation (strong rejection)


Factors affecting mental workload (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)


Factors affecting mental workload (cont.)

delays in system response mental models recognition vs recall controllability error tolerance environmental design social interaction time pressure


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


increased need for instruction

narrowing of attention erratic operation of

controls mistiming of actions making unnecessary

responses carrying out irrelevant

tasks

General principles of software ergonomics

Appropriate software 1. is suitable to the task2. is easy to use and adaptable3. provides feedback on system

performance4. works at the user’s own pace5. does not “spy” on the user.


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


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”Helsinki Metropolia University of Applied Sciences 1514.11.2010

3. Software provides feedback on system performance

timely error messages appropriate level of information task dependent help on request


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


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


Computer hasslesBy 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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HASSLES1. computer system is down2. lost in the computer3. poorly documented software4. computer hardware failure5. computer keyboard lockup6. programming error7. illegal input message8. updated software requirements9. poor user/computer interface10. slow program speed11. slow computer speed12. poorly written computer documentation13. incompatible software program14. incomprehensible computer instructions15. outdated computer skills16. increased time demands17. electrical surges - data are lost18. lost data

19. lost program20. crashed program21. crashed system/ lockup22. damaged storage media - disks, tapes23. need to update skills24. keyboard typing errors25. need to learn new software26. forgot to save work27. keyboard paralysis28. uninformative computer conversations29. violent language of computers30. too much computer information31. too little computer information32. software confusion33. lack of help with a computer problem34. lack of computer expertise35. increased computer use expectations36. lack of computer application software37. obsolete computers 20

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