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Development of non-keyboard input device checklists through assessments
ARTICLE IN PRESS
Applied Ergonomics 34 (2003) 511–519
Development of non-keyboard input device checklists through assessments Valerie Woodsa,*, Sarah Hastingsb, Peter Bucklea, Roger Haslamb b
a Robens Centre for Health Ergonomics, University of Surrey, Guildford GU2 7TE, UK Health and Safety Ergonomics Unit, Loughborough University, Leicestershire LE11 3TU, UK
Received 9 August 2001; accepted 3 July 2003
Abstract An assessment of non-keyboard input devices (NKID) was conducted to identify factors for good design in relation to operation, performance and comfort. Twenty-seven NKID users, working in health and safety, evaluated eight devices that included mice, trackballs and a joystick mouse. The factors considered important for good design were: (1) comfortable hand and finger position, (2) adequate control, (3) intuitive and easy to use, (4) ease of device, button and trackball movement, (5) good interaction with software, (6) provision of suitable accessories. Mice were rated more favourably than trackballs or the joystick mouse. The design of the standard 2-button mouse (D4) was considered most desirable to use; the 3-button mouse (D1) and 3-button curved mouse (D8) were also favoured. Assessment data and comments were drawn together with previously published research to produce useful tools for NKID purchasing (i.e. Device Purchasing Checklist) and assessment (i.e. Device Assessment Checklist). r 2003 Elsevier Ltd. All rights reserved. Keywords: Non-keyboard input devices; Design; Checklists
1. Introduction There has been a rapid growth in recent years in the range of non-keyboard input devices (NKID) utilised with computer systems (e.g. trackball, touchscreen, touch pad and trackpoint). All these devices have the same function, to place the cursor on the computer screen for the command or action required (Fernstrom and Ericson, 1997). However, concern that NKID use may predispose people to musculoskeletal injury has been documented (Cook et al., 2000; Keir et al., 1998; Harvey and Peper, 1997). NKID are generally operated in fairly static postures and the movements required are concentrated on the fingers, wrist, arm and shoulder but it is apparent from a small number of studies that different devices require different postures to operate them. Mouse use appears to be associated with raised levels of muscle activity in the shoulder region, abducted arms, and ulnar deviation of the wrist (Harvey and Peper, 1997), the trackball with more wrist extension (Burgess-Limerick and Green, *Corresponding author. E-mail address: [email protected] (V. Woods). 0003-6870/$ - see front matter r 2003 Elsevier Ltd. All rights reserved. doi:10.1016/j.apergo.2003.07.002
2000). Fernstrom and Ericson (1997) found decreased shoulder activity with trackpoint use in comparison with mouse use. The muscle load of the forearm was significantly less when using a joystick (vertical) mouse, compared with the traditional mouse (Aaras et al., 1997); however, Straker et al. (2000) reported that this vertical mouse was less easy to use (i.e. ease of movement, slow performance) than the traditional mouse. Studies have indicated that the location of NKID on the desk (Rurkhamet and Nanthavanij, 2000; Cook and Kothiyal, 1998), support for the upper limb during use (Cooper and Straker, 1998; Karlqvist, 1997), posture while using NKID (Matias et al., 1998; Mackinnon and Novak, 1997) and intensity of use (Hagberg, 1995) are important for user comfort and musculoskeletal health. However, only limited research (BS EN ISO 92419:2000, 2000; Armstrong et al., 1995) has been conducted on user preferences with regard to aspects of device design (e.g. what device features are particularly useful, how many buttons should be on a device?). A 2-year cross-sectional study in the UK (Woods et al., 2002) explored the extent and method of NKID use, device design, workstation configurations, postures
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adopted and prevalence of musculoskeletal symptoms in relation to NKID use by using questionnaires, workplace interviews and observations, an assessment of device design and laboratory trials. The results of the assessment of device design are reported in this paper. 1.1. Aims Given the lack of information available on NKID design to guide individual users, workplace health and safety managers, equipment purchasers and designers and manufacturers of devices, the aim of the assessment was to identify factors for good device design in relation to operation, performance and comfort to inform future device designs. A secondary aim was to develop checklists of factors to aid the choice and assessment of devices.
assessment as they were used with laptops and although touchscreen use is increasing, it was not common in the workplaces surveyed (ibid). The devices (D1–D8) assessed were (Fig. 1): D1. 3-button mouse, oval shape, for either hand. D2. 4-button (3 thumb, 1 finger) trackball, curved, support for hand/wrist, for right hand. D3. 1-button joystick or vertical mouse, support for wrist, for right hand. D4. standard 2-button mouse, curved, for right hand. D5. 4-button mouse with scroll, curved dome, for either hand. D6. 2-button (for thumb) trackball with scroll, space to rest hand/wrist, for right hand. D7. 2-button trackball, curved, for either hand. D8. 3-button (1 thumb, 2 fingers) mouse with scroll, curved, for right hand.
2. Method
2.3. Experimental design
2.1. Subjects
The study used a quasi-experimental design. The assessment took place over 2 days. Each of the eight devices was set-up at different workstations. All workstation configurations were the same: the desktop computer was placed in the deepest corner of a curved desk. The assessors were allowed to adjust the chairs to suit themselves and to place the NKID in an appropriate position for use. However, the mats (where required for use with the mouse) differed in texture (i.e. plastic or foam) from desk to desk. For practical reasons the study order could not be fully balanced or randomised; however no two subjects completed the evaluation in the same order. The assessors were requested to provide background information (e.g. age, hours using computers, devices used), to conduct three tasks with a device and to complete a questionnaire about this device. The evaluation took approximately 12 min: 1–2 min for each task followed by the completion of the device questionnaire. An assessment time of this length has been used in . previous NKID studies (Wahlstrom et al., 2000; Karlqvist, 1997). The subjects were asked to assess as many devices as time allowed. Due to the nature of the study design, time was limited, the average number of devices assessed by each subject was 4 (SD=2.5). All devices were assessed by at least 11 subjects (mean=12.9; SD=1.4; range=11–15). The three tasks were designed so that the major functions of devices were utilised (e.g. clicking, dragging, cutting, pasting, highlighting, scrolling). Task 1 required the subjects to answer a questionnaire; the subject scrolled through information on the computer screen, selected and clicked answers. Task 2 was an editing task that required cutting, pasting and highlighting within a paragraph of text on the screen. Task 3
Twenty-seven subjects assessed a range of NKID. All worked in the field of health and safety (e.g. ergonomists, physiotherapists, health and safety advisers and researchers/lecturers). The majority (82%) were right handed. Sixty-eight per cent were male and 32% were female. The mean age was 38.4 years (SD=9.1). Only 21 subjects provided details of their computer and NKID use. The mean number of years using computers was 15.6 (SD=7.6) and the mean number of years using NKID was 9.9 (SD=3.1). All assessors used a desktop computer on a daily basis while a small number (n ¼ 4) also used a laptop. The average daily desktop usage was 4.9 h (SD=2.2), the mean number of hours per day using laptops was 3 (SD=2.8). The majority used a mouse or a remote mouse on a daily basis with their right hand (86%), 5% with their left hand and 14% with either hand. Other NKID were also used by the group to some extent. About 5% used a touchpad (with laptop) on a daily basis, an additional 52% used this device infrequently. Trackballs (33%), touchscreens (29%), joysticks (29%) and computer pens (5%) were also used on an infrequent basis. 2.2. Devices Devices included in the assessment were considered to be representative in terms of design (e.g. shape, size, number of buttons and controls) of the devices reported to be used and also observed in use with desktop computers in the earlier parts of the study (Woods et al., 2002). This study also indicated that the most commonly used devices with desktop computers were the mouse and trackball. Touchpads were not included in this
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Fig. 1. NKIDs assessed by subjects.
required the subject to pick up a variety of shapes and drag and drop them into different positions on the screen. The task order was the same throughout for each device: task 1, task 2, then task 3.
*
*
2.4. Questionnaire design *
A questionnaire was devised based on previous research in this area (BS EN ISO 9241-9:2000, 2000; Armstrong et al., 1995) and the findings of other parts of this study (Woods et al., 2002). Subjects responded on 5point scales (disagree strongly to agree strongly) to a list of statements related to four areas of device usage: *
Device operation, e.g. ‘It is obvious how to operate the device’, ‘The input device is easy to use’
Device performance, e.g. ‘This input device responds as I’d expect’, ‘I had the right level of control over what I wanted to do’ Device design, e.g. ‘The design of the device prevents inadvertent button activation’, ‘The shape of the device is satisfactory’ Device comfort, e.g. ‘The input device can be operated without undue deviations of the wrist from a neutral posture’, ‘The input device does not cause pressure points that lead to discomfort during use’.
Using 5-point scales, information was also requested on ‘overall satisfaction’, ‘general comfort’ and ‘overall operation of the device’. Subjective comments about devices were also sought.
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2.5. Data analysis The data was analysed using SPSS version 11.0.0 (2001). The results presented are descriptive; no detailed statistical analysis was undertaken.
3. Results The questionnaire responses are presented in five sections: (1) operation, (2) performance, (3) design, (4) comfort, and (5) subjective comments. 3.1. Operation On the overall operation scale (very difficult to use– very easy to use), D1 (3-button mouse) and D4 (standard mouse) were rated as easy to use by all. D8 (3-button curved mouse with scroll) was considered easy to use by approximately half the sample (56%), D6 (2button trackball with scroll) by 40% and D7 (2-button trackball) by 30%. D2 (4-buttoned trackball), D3 (joystick mouse) and D5 (4-button mouse with scroll) were considered easy to use by less than 10% of subjects. Looking in more detail at particular aspects of device operation (e.g. obvious how to use, operation speed), D1, D4 and D8 generally scored well on the majority of questions. D7, although not considered highly on the general operation scale, was regarded as acceptable on a number of specific operational questions. The percentage of assessors who agreed with the statements on device operation is presented in Table 1. These results indicate that
Table 2 Percentage (%) of assessors who agreed with questions on device performance Device performance Responds as would expect Operates in same manner for similar tasks Adequate feedback Precision adequate Responsiveness satisfactory Adequate control Allows precision task to be conducted Feedback provided for button actuation Not too sensitive Right level of control Easy to select information on screen Easy to place pointer Easy to move pointer around screen Comfortable level of force for actuation Smooth movement Accurate
*
*
*
*
D1
D2 D3 D4
93 29 93 57
D5 D6 D7 D8
25 83
92 8 92 50
33 67
64 91
56 80
79 21 50 21 36
50 25 33 25 8
92 33 84 16 92 8 100 0 92 8
68 42 33 33 25
64 27 55 46 18
81 87 87 81 75
93 50
75
85 67
66
64
81
100 50 96 7 86 21
67 8 25
92 64 92 18 100 27
60 10 30
50 20 20
92 69 75
86 21 86 21
17 33
92 18 100 46
50 50
10 80
94 93
71 55
58
91 55
70
90
56
79 64 71 18
50 8
91 55 100 20
60 20
67 20
81 60
84 100 100 100 93
A number of devices were too slow to use: over 70% were not satisfied with the speed of D5; D2, D3 and D7 were also regarded as slow to use. D2, D3, D5 and D6 required too much effort (i.e. not necessarily force, this could mean stretching to reach controls) to use. Interaction of the device with the software was not considered adequate for D2, D3, D5 and D6. Device cables did not interfere with the movement of any devices.
3.2. Performance *
*
Some devices were not considered intuitive to use: D2, D3 and D5. Over half the sample said it was easy to make mistakes with D2, D3, D5 and D7.
Table 1 Percentage (%) of assessors who agreed with questions on device operation Operation
D1 D2 D3 D4 D5 D6 D7 D8
Obvious how to operate device 93 14 42 100 Easy to discover how to operate 86 43 67 100 Easy to use 86 14 25 100 Did not make mistakes 100 43 43 92 Acceptable operation speed 79 46 50 100 Not complicated to use 100 50 67 100 Low effort required to operate 64 27 17 91 Cables do not interfere 93 93 83 85 with movement Adequate interaction between 86 29 33 100 hard and software
8 8 8 35 27 27 36 92
65 100 56 76 100 62 50 50 75 60 50 81 60 50 75 80 80 62 40 50 75 92 82 93
On the overall performance scale (very unsatisfactory to very satisfactory), all assessors were satisfied with the performance of D4 (standard mouse), 75% with D1 (3button mouse) and 56% with D8 (3-button curved mouse with scroll). Less than 25% of assessors were satisfied with the performance of D3 (joystick mouse), D5 (4-button mouse with scroll), D6 (2-button trackball with scroll) and D7 (2-button trackball). Looking in more detail at particular aspects of device performance (e.g. responds as expected, adequate control), D1, D4 and D8 generally scored well on the majority of questions. The percentage of assessors who agreed with each statement about device performance is presented in Table 2. These results indicate that *
17 50
73 75
Four devices (D2, D3, D5, D6) did not respond as many assessors expected; however, they were consistent in their response to similar tasks.
ARTICLE IN PRESS V. Woods et al. / Applied Ergonomics 34 (2003) 511–519 *
*
*
*
*
Feedback was less acceptable for D3 and D5 than for other devices. Five devices were not accurate, precise or responsive enough: D2, D3, D5, D6 and D7. D2 and D7 were considered too sensitive by half the sample. Selecting information and placing the pointer was considered difficult using D2, D3, D5, D6 and D7. All devices were considered by at least 50% of the sample to require adequate force for actuation and to be smooth to use.
3.3. Design The percentage of assessors who agreed with the statements about device design (e.g. grip comfort, size of device) is presented in Table 3. Only the designs of D1 (3-button mouse), D4 (standard mouse) and D8 (3button curved mouse with scroll) made the user feel positive about using the device. This indicates that a number of NKID designs are not optimal: *
*
The grip of some devices was not satisfactory (D2, D3, D5 and D7): difficult to grasp, position and to hold. The design did not prevent inadvertent button actuation or cursor movement on many devices. Only D1 and D4 scored well.
Table 3 Percentage (%) of assessors who agreed with questions on device design Device design
D1 D2 D3 D4 D5 D6 D7 D8
Design makes me feel 71 7 positive towards use Device design enhances its 57 14 operation Grip surface prevents 71 71 slipping Grasped easily 78 21 Can be positioned easily 86 64 Can be positioned quickly 71 57 Held without excessive effort 86 50 Design prevents inadvertent 50 29 button activation Shape of button assists 50 21 finger positioning Shape of button assists 64 29 button actuation Does not cause unintended 79 7 pointer movement Device accommodates 100 50 hand size Device is stable, does not 93 79 slip/rock Device weight does not 93 86 impair usability Satisfactory size 86 39 Satisfactory shape 57 21 Could reach all buttons 79 29
25
92 17
17
9 50
25
85
8
17
9 50
50
77 50
58
55 81
17 42 17 19 0
58 58 42 58 33
64 55 36 46 46
36
85 25
58
36 62
50
77 25
50
27 50
25
85
0
25
18 62
67
77 42
58
36 75
67
100 83
67
91 81
83
100 75
67
100 87
50 42 65
100 18 100 9 100 27
60 60 70
30 69 30 56 60 75
42 25 25 83 17
85 92 84 100 69
63 69 88 88 38
*
*
*
515
A number of devices were unsatisfactory in terms of size to accommodate the hand (D2, D5, D7) and this caused difficulty in reaching device buttons. Device shape and button shape were unsatisfactory on D2, D3, D5 and D7. All devices were considered stable and a suitable weight by at least 65% of subjects.
3.4. Comfort On the overall comfort scale (very uncomfortable to very comfortable), D4 (standard mouse) was rated as comfortable to use by all. D1 (3-button mouse) was considered comfortable by 73% and D8 (3-button curved mouse with scroll) by two-thirds of the sample (63%). D6 (2-button trackball with scroll), D7 (2-button trackball), D2 (4-buttoned trackball) and D3 (joystick mouse) were considered comfortable to use by less than 30%. D5 (4-button mouse with scroll) was comfortable for less than 10% of assessors. Looking in more detail at specific aspects of comfort, D1, D4 and D8 generally scored well on the majority of questions. The percentage of assessors who agreed with each statement about device comfort (e.g. does not cause wrist fatigue or pressure points) is presented in Table 4. These results indicate that *
*
*
Approximately half the sample thought using D2, D3, D5 and D7 resulted in pressure points. It was not possible to operate a number of devices without undue deviation of fingers (D2, D5, D6, D7), wrist (D5, D6) and shoulder/arm (D3) from neutral. After using the devices, at least 30% of assessors experienced fatigue in the fingers (D2, D5, D6, D7)
Table 4 Percentage (%) of assessors who agreed with questions on device comfort Device comfort Does not cause pressure points Used without deviations of hand Used without deviations of fingers Used without deviations of arm Used without deviations of shoulder Used without deviations of head Used without deviations of neck No finger fatigue No wrist fatigue No arm fatigue No shoulder fatigue No neck fatigue
D1
D2
D3
D7
D8
71
50
50
77 42
75
55
75
64
54
50
62 25
43
64
69
64
21
58
68 33
33
27
69
71
71
25
77 50
83
73
69
79
79
42
92 67
92
91
69
93
86
92 100 75
100 100
88
86
86
83
100
88
82 64 92 100 82 58 100 91 75 100 100 75 100 100 100
D4
D5 D6
85 58 100 100 100 100 100
45 36 73 91 91
91
70 60 87 80 60 75 100 90 75 100 100 94 100 100 100
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and wrist (D3, D5, D7). At least 25% experienced fatigue in the arm (D3, D5, D8) and shoulder (D3). 3.5. Subjective comments The subjective comments have been categorised into six areas and illustrated using negative and positive examples of the assessors comments. 3.5.1. Posture Negative comments were made in relation to support for arm/wrist, deviation of the wrist from neutral and maintaining awkward angles, e.g. ‘full support of the forearm seems to inhibit movement’, ‘requires hyperextension of the wrist and finger movement to roll the ball’. Positive comments related to hand and wrist position, e.g. ‘fitted well in hand’, ‘comfortable with neutral wrist posture’. 3.5.2. Comfort Negative comments were made regarding cramping (due to stretching), pain and fatigue in the fingers, back of hand, wrist and forearm, e.g. ‘fingers have to float above device when not used to avoid inadvertent activation of ball/buttons which leads to discomfort in wrist’, ‘experience cramping in ring finger’. Positive comments for comfort were general, e.g. ‘feels very comfortable’. 3.5.3. Design Negative comments were expressed about device size, built-in support, excessive number of buttons and unsatisfactory shape, e.g. ‘design too wide at front’, ‘easy to miss button for double click as there are two buttons close together’, ‘too big’ ‘the height of the platform under the wrist is too high’. Positive comments concerned shape, design and facilities, e.g. ‘liked shape’, ‘very nice aesthetics’, ‘like the good old 2-button mouse’ ‘lots of options for both fingers’, ‘scroll easy to use which reduced movement of wrist/hand’. 3.5.4. Performance Negative comments related to poor control, accuracy, precision, sensitivity and movement, e.g. ‘difficult to be accurate, not precise enough’, ‘very awkward and difficult to control for cut and paste’, ‘ball rolled very poorly’. Positive comments were also made about these performance aspects, e.g. ‘precise, very easy to move and use’, ‘works well’, ‘smooth’. 3.5.5. Operation Negative comments were made about effort required, lack of device information, not intuitive to use, easy to make mistakes, e.g. ‘high perceived effort’, ‘easy to accidentally operate the ball’, ‘the function of the middle button is not self-evident’, ‘needs software adjustment to
increase pointer speed’. Positive comments were made about effort and interaction with software, e.g. ‘not much effort required, like light level of pressure needed for two upper buttons’, ‘good interaction with software’. 3.5.6. Additional Comments were also made regarding the importance of providing appropriate accessories, e.g. ‘mouse mat had very low friction so impedes performance’, ‘need larger mat’. 4. Discussion 4.1. Study design There were a number of limitations with the design of this study. It is recognised that subject numbers were small and as a result both left- and right-handed subjects were included; however, the majority of theleft-handed subjects normally used the right hand for device operation. In addition, the presentation of devices was not balanced and not all subjects evaluated each device. The intention of this study was to gather data from an informed and knowledgeable group about important design factors for NKID; it was recognised from the outset that the study group was not representative of the general population. Familiarity with use of the mouse may have influenced the assessments and it is acknowledged that the effect of learning would perhaps change the ratings over time, in particular, for those devices that differed most from the standard designs. Giving the assessors longer to become familiar with the devices would have been preferable and measuring hand dimensions would have been very informative with regard to device size. Regardless of these limitations, the assessment raised important points for the design, choice and assessment of any NKID. 4.2. Device preferences The analysis of overall ratings indicated that mice are rated more favourably in terms of overall satisfaction, operation and comfort than trackballs or the joystick mouse. It appears that the standard 2-button mouse (D4) is still the most popular device but that the 3button mouse (D1) and the 3-button curved mouse (D8) were also liked. 4.3. Device design The main factors highlighted in the assessment for good device design were the requirement for (1) Comfortable hand and finger position, i.e. comfortable device size and shape; appropriate button size, position and shape.
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(2) Adequate control of device, i.e. allows the user to be accurate and precise; not too sensitive. (3) Intuitive and easy to use, i.e. obvious how to use; straightforward button function. (4) Ease of device, buttons and trackball movement, i.e. easy to reach controls, smooth movement of ball, adequate feedback from action. (5) Good interaction with software, i.e. easy to change settings for pointer speed. Name: Dominant hand: Device: More than one desk: Time working on computer Less than 2 hours
2-4 hours
4 hours or more
517
(6) Suitable accessories, i.e. adequate sized mouse mat, appropriate texture of mat. In general all the designs assessed were considered satisfactory in terms of adequate force for actuation, smooth movement, stability and weight but it is evident from the results that many devices did not meet the above requirements. Device designers and manufacturers should conduct research and user trials on new Job: Desktop PC or laptop: Wrist support: Time using this device:
Intensity of use OCCASIONAL (hand on device from time to time during work tasks) REGULAR (hand moving between keyboard and device during work tasks) CONTINUAL (hand constantly on device during work tasks)
Breaks from computer REGULARLY (more than 2 in hour) OCCASIONAL (less than 2 in hour)
VERY RARELY (not every hour)
Have you had training to use the device? Is the device within easy reach i.e. you do not have to stretch to use it? Is the device suitable for the layout of the desk?
Yes Yes Yes
No No No
Yes
No
Yes Yes Yes
No No No
Yes
No
Device operation Is the device easy and intuitive to use? Do you know the function of all buttons/controls on the device? Can you work at the speed you want to using the device? Does the device require an acceptable amount of effort to operate it? Do the cables interfere with the operation of the device? Do you find that the device works well with the software you use? Is the size of the mouse mat appropriate? Is the material of the mouse mat appropriate?
Yes Yes Yes Yes No Yes Yes Yes
No No No No Yes No No No
Device design Is the size of the device suitable for your hand? Is the shape of the device satisfactory for you? Is the grip comfortable i.e. does not slip, can be grasped easily? Can the device be positioned easily and quickly? Is inadvertent button activation a problem with this device? Can you easily reach all the device buttons or other controls? Is the device stable i.e. does not slip/rock?
Yes Yes Yes Yes Yes Yes Yes
No No No No No No No
Device comfort Are your hand/fingers in a comfortable position using the device? Does the device cause pressure points that result in discomfort? Do you experience finger fatigue when using or after using the device? Do you experience wrist fatigue when using or after using the device? Do you experience arm fatigue when using or after using the device? Do you experience shoulder fatigue when using or after using the device?
Yes No No No No No
No Yes Yes Yes Yes Yes
Device performance Does the device respond as you would expect, i.e. in the same manner for similar tasks? Does the device give you adequate feedback when you press a button? Is the device responsive and sensitive enough? Do you have adequate control of the device, i.e. easy to place/move pointer to select information, no unintended pointer movement? Does the device (including buttons, trackball) move smoothly and easily?
Fig. 2. Device Assessment Checklist.
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Do you experience neck fatigue when using or after using the device? Is the device suitable for your dominant hand? Can the device be operated without undue deviations of wrist from neutral? Can the device be operated without undue deviations of fingers from neutral? Can the device be operated without undue deviations of arm from neutral? Can the device be operated without undue deviations of shoulder from neutral? Can the device be operated without undue deviations of neck from neutral?
DEVICE SUMMARY:
No Yes Yes Yes Yes Yes Yes
Yes No No No No No No
ACCEPTABLE - NOT ACCEPTABLE - WORKSTATION NEEDS MODIFICATION
ACTIONS
Fig. 2 (continued).
and existing devices to ensure that good design requirements are met. From the comments and ratings given by assessors in this study, designers and manufacturers need to consider the following: *
*
*
*
*
*
Provision of good information on device use, e.g. how to use and set all facilities. Provision of a range of device sizes; it is recognised that some manufacturers already do. Shape of devices, e.g. the benefits of domed and curved devices and built-in support. Size of devices, e.g. D2 was 7 cm high, how many people can use this comfortably to reach all the controls. Buttons and controls, e.g. size of rollerball, number of buttons that are of use and are straightforward to operate and program, shape and positioning of controls for smooth operation by thumb and fingers. Only D1 and D4 scored well on their design preventing inadvertent button actuation; these were the devices with the least number of buttons and the simplest layout. Device grip, e.g. D8 was the only device with a textured surface and this was rated highly in the assessment.
4.4. NKID checklists Given the large number of people (both at home and at work) who are reliant on NKID to interact with their computers, the findings of this assessment along with previously published research have been incorporated into a Device Purchasing Checklist and a Device
Assessment Checklist to assist with the choice and assessment of devices. These checklists revolve around the six factors identified as important for good device design in relation to operation, performance and comfort by the assessors in this study. 4.4.1. Device Purchasing Checklist It is important for any individual purchasing a new device for home or work, or for those in charge of equipment purchasing at organisations to consider: 1. 2. 3. 4. 5. 6. 7. 8.
Trying before buying, Does the device fit the hand of the user? Can the user reach all the controls on the device? Is inadvertent button activation a problem? Is it intuitive and straightforward to use? Can the user be accurate with the device? Are you just buying it for ‘looks’? Is it suitable/compatible for all the software applications the user works with?
4.4.2. Device Assessment Checklist A Device Assessment Checklist was designed to assist in the assessment of NKID use (Fig. 2). This could be used as part of a display screen assessment at work by health and safety personnel or by individual workers to assess their preference for a range of available input devices at work. It collects data on the individual, assesses the intensity of NKID use (e.g. an individual using a device for 4 h or more is an intensive user and problems identified by the checklist are vital to rectify) and investigates device operation, performance, design and comfort. An area to document actions is provided.
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5. Conclusions It was evident from this study that the simple design of the standard mouse was satisfactory. New, well designed and intuitive devices should be welcomed on the market but these must incorporate the requirements for good design outlined in this paper and the results of user trials conducted by the manufacturer/designer on the new product. Further research on device design is required in a number of areas, e.g. device shape and size, grip texture and the benefits of using devices with in-built support. This paper has highlighted good design factors for NKID and provided practical and useful NKID checklists for * *
* *
anyone purchasing a device, those with responsibility for workstation set-up and assessment at the workplace, individual workers choosing from a range of devices, designers and manufacturers of equipment.
Acknowledgements The authors wish to acknowledge the manufacturers whose devices were evaluated in this assessment: Anir, Kensington, Logitech and Microsoft. References Aaras, A., Fostervold, K., Ro, O., Thorenson, M., Larsen, S., 1997. Postural load during VDU work: a comparison between various work postures. Ergonomics 40 (11), 1255–1268. Armstrong, T.J., Martin, B.J., Franzblau, A., Rempel, D.M., Johnson, P.W., 1995. Mouse input devices and work-related upper limb disorders. In: Grieco, A., Molteni, G. (Eds.), Work with Display Units 94. Selected Papers of the Fourth International Scientific Conference on Work with Display Units, Milan, Italy, 2–5 October. Elsevier, Amsterdam, pp. 375–380. BS EN ISO 9241-9:2000, 2000. Ergonomic requirements for office work with visual display terminals (VDTs)-Part 9: requirements for non-keyboard input devices. ISO, Geneva. Burgess-Limerick, R., Green, B., 2000. Using multiple case studies in ergonomics: an example of pointing device use. Int. J. Ind. Ergon. 26, 381–388. Cook, C., Kothiyal, K., 1998. Influence of mouse position on muscular activity in the neck, shoulder and arm in computer users. Appl. Ergon. 29 (6), 439–443.
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Cook, C., Burgess-Limerick, R., Chang, S., 2000. The prevalence of neck and upper extremity musculoskeletal symptoms in computer mouse users. Int. J. Ind. Ergon. 26 (3), 347–356. Cooper, A., Straker, L., 1998. Mouse versus keyboard use—a comparison of shoulder muscle load. Int. J. Ind. Ergon. 22, 351–357. Fernstrom, E., Ericson, M.O., 1997. Computer mouse or trackpointeffects on muscular load and operator experience. Appl. Ergon. 28, 347–354. Hagberg, M., 1995. The ‘‘mouse-arm syndrome’’—concurrence of musculoskeletal symptoms and possible pathogenesis among VDU operators. In: Grieco, A., Molteni, G. (Eds.), Work with Display Units 94. Selected Papers of the Fourth International Scientific Conference on Work with Display Units, Milan, Italy, 2–5 October. Elsevier, Amsterdam, pp. 381–385. Harvey, R., Peper, E., 1997. Surface electromyography and mouse use position. Ergonomics 40, 781–789. Karlqvist, L., 1997. Assessment of physical work load at visual display unit workstations, ergonomic applications and gender aspects. Ph.D. Thesis, Department of Occupational Health, Karolinska Hospital, Stockholm, Sweden. Keir, P.J., Bach, J.M., Rempel, D.M., 1998. Fingertip loading and carpal tunnel pressure: differences between a pinching and pressing task. J. Orthop. Res. 16, 112–115. Mackinnon, S.E., Novak, C.B., 1997. Repetitive use and static postures: a source of nerve compression and pain. J. Hand Ther. 10 (2), 151–159. Matias, A.C., Salvendy, G., Kuczek, T., 1998. Predictive models of carpal tunnel syndrome causation among VDT operators. Ergonomics 41 (2), 213–226. Rurkhamet, B., Nanthavanij, S., 2000. Effects of dominant input device and its position on perceived upper extremity discomforts among Thai VDT users. In: Ergonomics for the New Millennium. Proceedings of the XIVth Triennial Congress of the International Ergonomics Association and the 44th Annual Meeting of the Human Factors and Ergonomics Society, San Diego, CA, July 29–August 4, 6, pp. 702–705. SPSS, 2001. Statistical Package for the Social Sciences for Windows, Release 11.0.0, SPSS Inc., Chicago, IL. Straker, L., Pollock, C., Frosh, A., Aaras, A., Dainoff, M., 2000. An ergonomic field comparison of a traditional computer mouse and a vertical computer mouse in uninjured office workers. Ergonomics for the New Millennium. Proceedings of the XIVth Triennial Congress of the International Ergonomics Association and the 44th Annual Meeting of the Human Factors and Ergonomics Society, San Diego, CA, July 29–August 4, 6, pp. 356–359. Wahlstr.om, J., Svensson, J., Hagberg, M., Johnson, P., 2000. Differences between work methods and gender in computer mouse use. Scand. J. Work Environ. Health 26, 390–397. Woods, V., Hastings, S., Buckle, P., Haslam, R., 2002. Ergonomics of Using a Mouse or Other Non-Keyboard Input Device. HSE Books, Suffolk.
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Development of non-keyboard input device checklists through assessments Valerie Woodsa,*, Sarah Hastingsb, Peter Bucklea, Roger Haslamb b
a Robens Centre for Health Ergonomics, University of Surrey, Guildford GU2 7TE, UK Health and Safety Ergonomics Unit, Loughborough University, Leicestershire LE11 3TU, UK
Received 9 August 2001; accepted 3 July 2003
Abstract An assessment of non-keyboard input devices (NKID) was conducted to identify factors for good design in relation to operation, performance and comfort. Twenty-seven NKID users, working in health and safety, evaluated eight devices that included mice, trackballs and a joystick mouse. The factors considered important for good design were: (1) comfortable hand and finger position, (2) adequate control, (3) intuitive and easy to use, (4) ease of device, button and trackball movement, (5) good interaction with software, (6) provision of suitable accessories. Mice were rated more favourably than trackballs or the joystick mouse. The design of the standard 2-button mouse (D4) was considered most desirable to use; the 3-button mouse (D1) and 3-button curved mouse (D8) were also favoured. Assessment data and comments were drawn together with previously published research to produce useful tools for NKID purchasing (i.e. Device Purchasing Checklist) and assessment (i.e. Device Assessment Checklist). r 2003 Elsevier Ltd. All rights reserved. Keywords: Non-keyboard input devices; Design; Checklists
1. Introduction There has been a rapid growth in recent years in the range of non-keyboard input devices (NKID) utilised with computer systems (e.g. trackball, touchscreen, touch pad and trackpoint). All these devices have the same function, to place the cursor on the computer screen for the command or action required (Fernstrom and Ericson, 1997). However, concern that NKID use may predispose people to musculoskeletal injury has been documented (Cook et al., 2000; Keir et al., 1998; Harvey and Peper, 1997). NKID are generally operated in fairly static postures and the movements required are concentrated on the fingers, wrist, arm and shoulder but it is apparent from a small number of studies that different devices require different postures to operate them. Mouse use appears to be associated with raised levels of muscle activity in the shoulder region, abducted arms, and ulnar deviation of the wrist (Harvey and Peper, 1997), the trackball with more wrist extension (Burgess-Limerick and Green, *Corresponding author. E-mail address: [email protected] (V. Woods). 0003-6870/$ - see front matter r 2003 Elsevier Ltd. All rights reserved. doi:10.1016/j.apergo.2003.07.002
2000). Fernstrom and Ericson (1997) found decreased shoulder activity with trackpoint use in comparison with mouse use. The muscle load of the forearm was significantly less when using a joystick (vertical) mouse, compared with the traditional mouse (Aaras et al., 1997); however, Straker et al. (2000) reported that this vertical mouse was less easy to use (i.e. ease of movement, slow performance) than the traditional mouse. Studies have indicated that the location of NKID on the desk (Rurkhamet and Nanthavanij, 2000; Cook and Kothiyal, 1998), support for the upper limb during use (Cooper and Straker, 1998; Karlqvist, 1997), posture while using NKID (Matias et al., 1998; Mackinnon and Novak, 1997) and intensity of use (Hagberg, 1995) are important for user comfort and musculoskeletal health. However, only limited research (BS EN ISO 92419:2000, 2000; Armstrong et al., 1995) has been conducted on user preferences with regard to aspects of device design (e.g. what device features are particularly useful, how many buttons should be on a device?). A 2-year cross-sectional study in the UK (Woods et al., 2002) explored the extent and method of NKID use, device design, workstation configurations, postures
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adopted and prevalence of musculoskeletal symptoms in relation to NKID use by using questionnaires, workplace interviews and observations, an assessment of device design and laboratory trials. The results of the assessment of device design are reported in this paper. 1.1. Aims Given the lack of information available on NKID design to guide individual users, workplace health and safety managers, equipment purchasers and designers and manufacturers of devices, the aim of the assessment was to identify factors for good device design in relation to operation, performance and comfort to inform future device designs. A secondary aim was to develop checklists of factors to aid the choice and assessment of devices.
assessment as they were used with laptops and although touchscreen use is increasing, it was not common in the workplaces surveyed (ibid). The devices (D1–D8) assessed were (Fig. 1): D1. 3-button mouse, oval shape, for either hand. D2. 4-button (3 thumb, 1 finger) trackball, curved, support for hand/wrist, for right hand. D3. 1-button joystick or vertical mouse, support for wrist, for right hand. D4. standard 2-button mouse, curved, for right hand. D5. 4-button mouse with scroll, curved dome, for either hand. D6. 2-button (for thumb) trackball with scroll, space to rest hand/wrist, for right hand. D7. 2-button trackball, curved, for either hand. D8. 3-button (1 thumb, 2 fingers) mouse with scroll, curved, for right hand.
2. Method
2.3. Experimental design
2.1. Subjects
The study used a quasi-experimental design. The assessment took place over 2 days. Each of the eight devices was set-up at different workstations. All workstation configurations were the same: the desktop computer was placed in the deepest corner of a curved desk. The assessors were allowed to adjust the chairs to suit themselves and to place the NKID in an appropriate position for use. However, the mats (where required for use with the mouse) differed in texture (i.e. plastic or foam) from desk to desk. For practical reasons the study order could not be fully balanced or randomised; however no two subjects completed the evaluation in the same order. The assessors were requested to provide background information (e.g. age, hours using computers, devices used), to conduct three tasks with a device and to complete a questionnaire about this device. The evaluation took approximately 12 min: 1–2 min for each task followed by the completion of the device questionnaire. An assessment time of this length has been used in . previous NKID studies (Wahlstrom et al., 2000; Karlqvist, 1997). The subjects were asked to assess as many devices as time allowed. Due to the nature of the study design, time was limited, the average number of devices assessed by each subject was 4 (SD=2.5). All devices were assessed by at least 11 subjects (mean=12.9; SD=1.4; range=11–15). The three tasks were designed so that the major functions of devices were utilised (e.g. clicking, dragging, cutting, pasting, highlighting, scrolling). Task 1 required the subjects to answer a questionnaire; the subject scrolled through information on the computer screen, selected and clicked answers. Task 2 was an editing task that required cutting, pasting and highlighting within a paragraph of text on the screen. Task 3
Twenty-seven subjects assessed a range of NKID. All worked in the field of health and safety (e.g. ergonomists, physiotherapists, health and safety advisers and researchers/lecturers). The majority (82%) were right handed. Sixty-eight per cent were male and 32% were female. The mean age was 38.4 years (SD=9.1). Only 21 subjects provided details of their computer and NKID use. The mean number of years using computers was 15.6 (SD=7.6) and the mean number of years using NKID was 9.9 (SD=3.1). All assessors used a desktop computer on a daily basis while a small number (n ¼ 4) also used a laptop. The average daily desktop usage was 4.9 h (SD=2.2), the mean number of hours per day using laptops was 3 (SD=2.8). The majority used a mouse or a remote mouse on a daily basis with their right hand (86%), 5% with their left hand and 14% with either hand. Other NKID were also used by the group to some extent. About 5% used a touchpad (with laptop) on a daily basis, an additional 52% used this device infrequently. Trackballs (33%), touchscreens (29%), joysticks (29%) and computer pens (5%) were also used on an infrequent basis. 2.2. Devices Devices included in the assessment were considered to be representative in terms of design (e.g. shape, size, number of buttons and controls) of the devices reported to be used and also observed in use with desktop computers in the earlier parts of the study (Woods et al., 2002). This study also indicated that the most commonly used devices with desktop computers were the mouse and trackball. Touchpads were not included in this
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Fig. 1. NKIDs assessed by subjects.
required the subject to pick up a variety of shapes and drag and drop them into different positions on the screen. The task order was the same throughout for each device: task 1, task 2, then task 3.
*
*
2.4. Questionnaire design *
A questionnaire was devised based on previous research in this area (BS EN ISO 9241-9:2000, 2000; Armstrong et al., 1995) and the findings of other parts of this study (Woods et al., 2002). Subjects responded on 5point scales (disagree strongly to agree strongly) to a list of statements related to four areas of device usage: *
Device operation, e.g. ‘It is obvious how to operate the device’, ‘The input device is easy to use’
Device performance, e.g. ‘This input device responds as I’d expect’, ‘I had the right level of control over what I wanted to do’ Device design, e.g. ‘The design of the device prevents inadvertent button activation’, ‘The shape of the device is satisfactory’ Device comfort, e.g. ‘The input device can be operated without undue deviations of the wrist from a neutral posture’, ‘The input device does not cause pressure points that lead to discomfort during use’.
Using 5-point scales, information was also requested on ‘overall satisfaction’, ‘general comfort’ and ‘overall operation of the device’. Subjective comments about devices were also sought.
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2.5. Data analysis The data was analysed using SPSS version 11.0.0 (2001). The results presented are descriptive; no detailed statistical analysis was undertaken.
3. Results The questionnaire responses are presented in five sections: (1) operation, (2) performance, (3) design, (4) comfort, and (5) subjective comments. 3.1. Operation On the overall operation scale (very difficult to use– very easy to use), D1 (3-button mouse) and D4 (standard mouse) were rated as easy to use by all. D8 (3-button curved mouse with scroll) was considered easy to use by approximately half the sample (56%), D6 (2button trackball with scroll) by 40% and D7 (2-button trackball) by 30%. D2 (4-buttoned trackball), D3 (joystick mouse) and D5 (4-button mouse with scroll) were considered easy to use by less than 10% of subjects. Looking in more detail at particular aspects of device operation (e.g. obvious how to use, operation speed), D1, D4 and D8 generally scored well on the majority of questions. D7, although not considered highly on the general operation scale, was regarded as acceptable on a number of specific operational questions. The percentage of assessors who agreed with the statements on device operation is presented in Table 1. These results indicate that
Table 2 Percentage (%) of assessors who agreed with questions on device performance Device performance Responds as would expect Operates in same manner for similar tasks Adequate feedback Precision adequate Responsiveness satisfactory Adequate control Allows precision task to be conducted Feedback provided for button actuation Not too sensitive Right level of control Easy to select information on screen Easy to place pointer Easy to move pointer around screen Comfortable level of force for actuation Smooth movement Accurate
*
*
*
*
D1
D2 D3 D4
93 29 93 57
D5 D6 D7 D8
25 83
92 8 92 50
33 67
64 91
56 80
79 21 50 21 36
50 25 33 25 8
92 33 84 16 92 8 100 0 92 8
68 42 33 33 25
64 27 55 46 18
81 87 87 81 75
93 50
75
85 67
66
64
81
100 50 96 7 86 21
67 8 25
92 64 92 18 100 27
60 10 30
50 20 20
92 69 75
86 21 86 21
17 33
92 18 100 46
50 50
10 80
94 93
71 55
58
91 55
70
90
56
79 64 71 18
50 8
91 55 100 20
60 20
67 20
81 60
84 100 100 100 93
A number of devices were too slow to use: over 70% were not satisfied with the speed of D5; D2, D3 and D7 were also regarded as slow to use. D2, D3, D5 and D6 required too much effort (i.e. not necessarily force, this could mean stretching to reach controls) to use. Interaction of the device with the software was not considered adequate for D2, D3, D5 and D6. Device cables did not interfere with the movement of any devices.
3.2. Performance *
*
Some devices were not considered intuitive to use: D2, D3 and D5. Over half the sample said it was easy to make mistakes with D2, D3, D5 and D7.
Table 1 Percentage (%) of assessors who agreed with questions on device operation Operation
D1 D2 D3 D4 D5 D6 D7 D8
Obvious how to operate device 93 14 42 100 Easy to discover how to operate 86 43 67 100 Easy to use 86 14 25 100 Did not make mistakes 100 43 43 92 Acceptable operation speed 79 46 50 100 Not complicated to use 100 50 67 100 Low effort required to operate 64 27 17 91 Cables do not interfere 93 93 83 85 with movement Adequate interaction between 86 29 33 100 hard and software
8 8 8 35 27 27 36 92
65 100 56 76 100 62 50 50 75 60 50 81 60 50 75 80 80 62 40 50 75 92 82 93
On the overall performance scale (very unsatisfactory to very satisfactory), all assessors were satisfied with the performance of D4 (standard mouse), 75% with D1 (3button mouse) and 56% with D8 (3-button curved mouse with scroll). Less than 25% of assessors were satisfied with the performance of D3 (joystick mouse), D5 (4-button mouse with scroll), D6 (2-button trackball with scroll) and D7 (2-button trackball). Looking in more detail at particular aspects of device performance (e.g. responds as expected, adequate control), D1, D4 and D8 generally scored well on the majority of questions. The percentage of assessors who agreed with each statement about device performance is presented in Table 2. These results indicate that *
17 50
73 75
Four devices (D2, D3, D5, D6) did not respond as many assessors expected; however, they were consistent in their response to similar tasks.
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*
*
*
*
Feedback was less acceptable for D3 and D5 than for other devices. Five devices were not accurate, precise or responsive enough: D2, D3, D5, D6 and D7. D2 and D7 were considered too sensitive by half the sample. Selecting information and placing the pointer was considered difficult using D2, D3, D5, D6 and D7. All devices were considered by at least 50% of the sample to require adequate force for actuation and to be smooth to use.
3.3. Design The percentage of assessors who agreed with the statements about device design (e.g. grip comfort, size of device) is presented in Table 3. Only the designs of D1 (3-button mouse), D4 (standard mouse) and D8 (3button curved mouse with scroll) made the user feel positive about using the device. This indicates that a number of NKID designs are not optimal: *
*
The grip of some devices was not satisfactory (D2, D3, D5 and D7): difficult to grasp, position and to hold. The design did not prevent inadvertent button actuation or cursor movement on many devices. Only D1 and D4 scored well.
Table 3 Percentage (%) of assessors who agreed with questions on device design Device design
D1 D2 D3 D4 D5 D6 D7 D8
Design makes me feel 71 7 positive towards use Device design enhances its 57 14 operation Grip surface prevents 71 71 slipping Grasped easily 78 21 Can be positioned easily 86 64 Can be positioned quickly 71 57 Held without excessive effort 86 50 Design prevents inadvertent 50 29 button activation Shape of button assists 50 21 finger positioning Shape of button assists 64 29 button actuation Does not cause unintended 79 7 pointer movement Device accommodates 100 50 hand size Device is stable, does not 93 79 slip/rock Device weight does not 93 86 impair usability Satisfactory size 86 39 Satisfactory shape 57 21 Could reach all buttons 79 29
25
92 17
17
9 50
25
85
8
17
9 50
50
77 50
58
55 81
17 42 17 19 0
58 58 42 58 33
64 55 36 46 46
36
85 25
58
36 62
50
77 25
50
27 50
25
85
0
25
18 62
67
77 42
58
36 75
67
100 83
67
91 81
83
100 75
67
100 87
50 42 65
100 18 100 9 100 27
60 60 70
30 69 30 56 60 75
42 25 25 83 17
85 92 84 100 69
63 69 88 88 38
*
*
*
515
A number of devices were unsatisfactory in terms of size to accommodate the hand (D2, D5, D7) and this caused difficulty in reaching device buttons. Device shape and button shape were unsatisfactory on D2, D3, D5 and D7. All devices were considered stable and a suitable weight by at least 65% of subjects.
3.4. Comfort On the overall comfort scale (very uncomfortable to very comfortable), D4 (standard mouse) was rated as comfortable to use by all. D1 (3-button mouse) was considered comfortable by 73% and D8 (3-button curved mouse with scroll) by two-thirds of the sample (63%). D6 (2-button trackball with scroll), D7 (2-button trackball), D2 (4-buttoned trackball) and D3 (joystick mouse) were considered comfortable to use by less than 30%. D5 (4-button mouse with scroll) was comfortable for less than 10% of assessors. Looking in more detail at specific aspects of comfort, D1, D4 and D8 generally scored well on the majority of questions. The percentage of assessors who agreed with each statement about device comfort (e.g. does not cause wrist fatigue or pressure points) is presented in Table 4. These results indicate that *
*
*
Approximately half the sample thought using D2, D3, D5 and D7 resulted in pressure points. It was not possible to operate a number of devices without undue deviation of fingers (D2, D5, D6, D7), wrist (D5, D6) and shoulder/arm (D3) from neutral. After using the devices, at least 30% of assessors experienced fatigue in the fingers (D2, D5, D6, D7)
Table 4 Percentage (%) of assessors who agreed with questions on device comfort Device comfort Does not cause pressure points Used without deviations of hand Used without deviations of fingers Used without deviations of arm Used without deviations of shoulder Used without deviations of head Used without deviations of neck No finger fatigue No wrist fatigue No arm fatigue No shoulder fatigue No neck fatigue
D1
D2
D3
D7
D8
71
50
50
77 42
75
55
75
64
54
50
62 25
43
64
69
64
21
58
68 33
33
27
69
71
71
25
77 50
83
73
69
79
79
42
92 67
92
91
69
93
86
92 100 75
100 100
88
86
86
83
100
88
82 64 92 100 82 58 100 91 75 100 100 75 100 100 100
D4
D5 D6
85 58 100 100 100 100 100
45 36 73 91 91
91
70 60 87 80 60 75 100 90 75 100 100 94 100 100 100
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and wrist (D3, D5, D7). At least 25% experienced fatigue in the arm (D3, D5, D8) and shoulder (D3). 3.5. Subjective comments The subjective comments have been categorised into six areas and illustrated using negative and positive examples of the assessors comments. 3.5.1. Posture Negative comments were made in relation to support for arm/wrist, deviation of the wrist from neutral and maintaining awkward angles, e.g. ‘full support of the forearm seems to inhibit movement’, ‘requires hyperextension of the wrist and finger movement to roll the ball’. Positive comments related to hand and wrist position, e.g. ‘fitted well in hand’, ‘comfortable with neutral wrist posture’. 3.5.2. Comfort Negative comments were made regarding cramping (due to stretching), pain and fatigue in the fingers, back of hand, wrist and forearm, e.g. ‘fingers have to float above device when not used to avoid inadvertent activation of ball/buttons which leads to discomfort in wrist’, ‘experience cramping in ring finger’. Positive comments for comfort were general, e.g. ‘feels very comfortable’. 3.5.3. Design Negative comments were expressed about device size, built-in support, excessive number of buttons and unsatisfactory shape, e.g. ‘design too wide at front’, ‘easy to miss button for double click as there are two buttons close together’, ‘too big’ ‘the height of the platform under the wrist is too high’. Positive comments concerned shape, design and facilities, e.g. ‘liked shape’, ‘very nice aesthetics’, ‘like the good old 2-button mouse’ ‘lots of options for both fingers’, ‘scroll easy to use which reduced movement of wrist/hand’. 3.5.4. Performance Negative comments related to poor control, accuracy, precision, sensitivity and movement, e.g. ‘difficult to be accurate, not precise enough’, ‘very awkward and difficult to control for cut and paste’, ‘ball rolled very poorly’. Positive comments were also made about these performance aspects, e.g. ‘precise, very easy to move and use’, ‘works well’, ‘smooth’. 3.5.5. Operation Negative comments were made about effort required, lack of device information, not intuitive to use, easy to make mistakes, e.g. ‘high perceived effort’, ‘easy to accidentally operate the ball’, ‘the function of the middle button is not self-evident’, ‘needs software adjustment to
increase pointer speed’. Positive comments were made about effort and interaction with software, e.g. ‘not much effort required, like light level of pressure needed for two upper buttons’, ‘good interaction with software’. 3.5.6. Additional Comments were also made regarding the importance of providing appropriate accessories, e.g. ‘mouse mat had very low friction so impedes performance’, ‘need larger mat’. 4. Discussion 4.1. Study design There were a number of limitations with the design of this study. It is recognised that subject numbers were small and as a result both left- and right-handed subjects were included; however, the majority of theleft-handed subjects normally used the right hand for device operation. In addition, the presentation of devices was not balanced and not all subjects evaluated each device. The intention of this study was to gather data from an informed and knowledgeable group about important design factors for NKID; it was recognised from the outset that the study group was not representative of the general population. Familiarity with use of the mouse may have influenced the assessments and it is acknowledged that the effect of learning would perhaps change the ratings over time, in particular, for those devices that differed most from the standard designs. Giving the assessors longer to become familiar with the devices would have been preferable and measuring hand dimensions would have been very informative with regard to device size. Regardless of these limitations, the assessment raised important points for the design, choice and assessment of any NKID. 4.2. Device preferences The analysis of overall ratings indicated that mice are rated more favourably in terms of overall satisfaction, operation and comfort than trackballs or the joystick mouse. It appears that the standard 2-button mouse (D4) is still the most popular device but that the 3button mouse (D1) and the 3-button curved mouse (D8) were also liked. 4.3. Device design The main factors highlighted in the assessment for good device design were the requirement for (1) Comfortable hand and finger position, i.e. comfortable device size and shape; appropriate button size, position and shape.
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(2) Adequate control of device, i.e. allows the user to be accurate and precise; not too sensitive. (3) Intuitive and easy to use, i.e. obvious how to use; straightforward button function. (4) Ease of device, buttons and trackball movement, i.e. easy to reach controls, smooth movement of ball, adequate feedback from action. (5) Good interaction with software, i.e. easy to change settings for pointer speed. Name: Dominant hand: Device: More than one desk: Time working on computer Less than 2 hours
2-4 hours
4 hours or more
517
(6) Suitable accessories, i.e. adequate sized mouse mat, appropriate texture of mat. In general all the designs assessed were considered satisfactory in terms of adequate force for actuation, smooth movement, stability and weight but it is evident from the results that many devices did not meet the above requirements. Device designers and manufacturers should conduct research and user trials on new Job: Desktop PC or laptop: Wrist support: Time using this device:
Intensity of use OCCASIONAL (hand on device from time to time during work tasks) REGULAR (hand moving between keyboard and device during work tasks) CONTINUAL (hand constantly on device during work tasks)
Breaks from computer REGULARLY (more than 2 in hour) OCCASIONAL (less than 2 in hour)
VERY RARELY (not every hour)
Have you had training to use the device? Is the device within easy reach i.e. you do not have to stretch to use it? Is the device suitable for the layout of the desk?
Yes Yes Yes
No No No
Yes
No
Yes Yes Yes
No No No
Yes
No
Device operation Is the device easy and intuitive to use? Do you know the function of all buttons/controls on the device? Can you work at the speed you want to using the device? Does the device require an acceptable amount of effort to operate it? Do the cables interfere with the operation of the device? Do you find that the device works well with the software you use? Is the size of the mouse mat appropriate? Is the material of the mouse mat appropriate?
Yes Yes Yes Yes No Yes Yes Yes
No No No No Yes No No No
Device design Is the size of the device suitable for your hand? Is the shape of the device satisfactory for you? Is the grip comfortable i.e. does not slip, can be grasped easily? Can the device be positioned easily and quickly? Is inadvertent button activation a problem with this device? Can you easily reach all the device buttons or other controls? Is the device stable i.e. does not slip/rock?
Yes Yes Yes Yes Yes Yes Yes
No No No No No No No
Device comfort Are your hand/fingers in a comfortable position using the device? Does the device cause pressure points that result in discomfort? Do you experience finger fatigue when using or after using the device? Do you experience wrist fatigue when using or after using the device? Do you experience arm fatigue when using or after using the device? Do you experience shoulder fatigue when using or after using the device?
Yes No No No No No
No Yes Yes Yes Yes Yes
Device performance Does the device respond as you would expect, i.e. in the same manner for similar tasks? Does the device give you adequate feedback when you press a button? Is the device responsive and sensitive enough? Do you have adequate control of the device, i.e. easy to place/move pointer to select information, no unintended pointer movement? Does the device (including buttons, trackball) move smoothly and easily?
Fig. 2. Device Assessment Checklist.
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Do you experience neck fatigue when using or after using the device? Is the device suitable for your dominant hand? Can the device be operated without undue deviations of wrist from neutral? Can the device be operated without undue deviations of fingers from neutral? Can the device be operated without undue deviations of arm from neutral? Can the device be operated without undue deviations of shoulder from neutral? Can the device be operated without undue deviations of neck from neutral?
DEVICE SUMMARY:
No Yes Yes Yes Yes Yes Yes
Yes No No No No No No
ACCEPTABLE - NOT ACCEPTABLE - WORKSTATION NEEDS MODIFICATION
ACTIONS
Fig. 2 (continued).
and existing devices to ensure that good design requirements are met. From the comments and ratings given by assessors in this study, designers and manufacturers need to consider the following: *
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Provision of good information on device use, e.g. how to use and set all facilities. Provision of a range of device sizes; it is recognised that some manufacturers already do. Shape of devices, e.g. the benefits of domed and curved devices and built-in support. Size of devices, e.g. D2 was 7 cm high, how many people can use this comfortably to reach all the controls. Buttons and controls, e.g. size of rollerball, number of buttons that are of use and are straightforward to operate and program, shape and positioning of controls for smooth operation by thumb and fingers. Only D1 and D4 scored well on their design preventing inadvertent button actuation; these were the devices with the least number of buttons and the simplest layout. Device grip, e.g. D8 was the only device with a textured surface and this was rated highly in the assessment.
4.4. NKID checklists Given the large number of people (both at home and at work) who are reliant on NKID to interact with their computers, the findings of this assessment along with previously published research have been incorporated into a Device Purchasing Checklist and a Device
Assessment Checklist to assist with the choice and assessment of devices. These checklists revolve around the six factors identified as important for good device design in relation to operation, performance and comfort by the assessors in this study. 4.4.1. Device Purchasing Checklist It is important for any individual purchasing a new device for home or work, or for those in charge of equipment purchasing at organisations to consider: 1. 2. 3. 4. 5. 6. 7. 8.
Trying before buying, Does the device fit the hand of the user? Can the user reach all the controls on the device? Is inadvertent button activation a problem? Is it intuitive and straightforward to use? Can the user be accurate with the device? Are you just buying it for ‘looks’? Is it suitable/compatible for all the software applications the user works with?
4.4.2. Device Assessment Checklist A Device Assessment Checklist was designed to assist in the assessment of NKID use (Fig. 2). This could be used as part of a display screen assessment at work by health and safety personnel or by individual workers to assess their preference for a range of available input devices at work. It collects data on the individual, assesses the intensity of NKID use (e.g. an individual using a device for 4 h or more is an intensive user and problems identified by the checklist are vital to rectify) and investigates device operation, performance, design and comfort. An area to document actions is provided.
ARTICLE IN PRESS V. Woods et al. / Applied Ergonomics 34 (2003) 511–519
5. Conclusions It was evident from this study that the simple design of the standard mouse was satisfactory. New, well designed and intuitive devices should be welcomed on the market but these must incorporate the requirements for good design outlined in this paper and the results of user trials conducted by the manufacturer/designer on the new product. Further research on device design is required in a number of areas, e.g. device shape and size, grip texture and the benefits of using devices with in-built support. This paper has highlighted good design factors for NKID and provided practical and useful NKID checklists for * *
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anyone purchasing a device, those with responsibility for workstation set-up and assessment at the workplace, individual workers choosing from a range of devices, designers and manufacturers of equipment.
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