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Desktop virtual environments: a study of navigation and age
Interacting with Computers 16 (2004) 939–956 www.elsevier.com/locate/intcom
Desktop virtual environments: a study of navigation and age H. Sayers* School of Computing and Intelligent Systems, University of Ulster, Magee Campus, Londonderry BT48 7JL, UK Received 6 February 2004; revised 4 May 2004; accepted 13 May 2004 Available online 2 July 2004
Abstract Navigation in virtual environments on desktop systems is known to be problematic. Research into the usability of the tools presented on two-dimensional interfaces indicates that, for even relatively simple tasks, users experience some degree of frustration. As the user community broadens with an increasing range of applications and services making use of three-dimensional presentation, the usability of these interfaces becomes ever more important. In this paper, we describe the results of an experiment performed to evaluate the usability of a number of visual navigation tools and the effect for two age groups (18– 45 and 46 þ ). Results indicate that, for both age groups, the visual presentation of navigational aids improves navigation performance in terms of both time taken to complete tasks, and user satisfaction with the system. In all experimental conditions younger participants achieved better performance times, although the gap between the groups decreased when a choice of navigation aids was presented. q 2004 Elsevier B.V. All rights reserved. Keywords: Desktop virtual environments; Navigation; Age; Usability
1. Introduction A three-dimensional (3D) virtual environment (VE) is a computer representation of a real world space or an imaginary space through which users can navigate and in which they can interact with objects. Unlike fully immersive VEs which use specialised interaction devices such as head-mounted displays to create a sense of presence for the user within the 3D world, desktop systems exploit general-purpose hardware for interaction (PC, mouse, keyboard) and although obviously offer a much reduced sense of * Tel.: þ44-28-71375553; fax: þ44-28-71375470. E-mail address: [email protected] 0953-5438/$ - see front matter q 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.intcom.2004.05.003
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presence in the VE, are still useful for many application areas (Green and Jacob, 1991). The Virtual Reality Modeling Language (VRML), commonly supported by all popular Internet browsers, has opened up VE technology to a wide range of users using standard desktop systems. Research has shown that existing user interface guidelines do not address the particular requirements for interfaces to VEs, and no standard ‘look and feel’ has yet evolved for interfaces to 3D worlds (Hand, 1997). Users of VE applications, however, require intuitive tools to maximise their productivity. In VE applications, this need can be defined as the need for effective navigation and interaction. There has been much research into usability design for virtual environments themselves (Fencott, 1999; Kaur, 1998; Kaur Deol et al., 1999; Sayers et al., 1999), but little consideration has been given to the usability of the tools presented on interfaces to desktop VEs. There has also been little research into the effect of age on the usability of such tools. The population of the developed world is getting older, and the use of computers in everyday life is becoming more prevalent and indeed more necessary. In order to avoid social exclusion and to be able to live more independently, therefore, older adults will increasingly need to be able to use computers and computer systems (Zajicek, 2003). Hawthorn (2000) reports that in the United States, people over 45 years old will soon constitute over half of the adult population. Research has shown that older users (over 60 years), although willing to learn to use computers, consistently have more difficulty than younger people (Czaja, 1996). As older users become increasingly exposed to computer technology, understanding their unique requirements will become a much more important consideration in the design of human–computer interfaces than at present, and a body of research has begun to focus on human–computer interface design to assist interaction with two-dimensional applications for older users (Czaja, 1996; Mead et al., 1997; Worden et al., 1997). Hawthorn (2003) highlights the perceived changes in future older generations and computer experience (i.e. that the number of inexperienced older users will decrease) and believes that there is a very interesting and important research topic to be found in how today’s 40–60-year-old computer users will adapt to changes in computing technology as they get older. Older people are as diverse as younger people. Their exposure to computers, for example, will vary, with many having had little or none, while younger people have grown up with technology as an integral part of their lives. Changes in older adults’ abilities— physical and cognitive—also vary considerably (Rogers, 1997). A one-size-fits-all design approach is therefore inappropriate for this user group (Browne, 2000). Research has acknowledged the importance of involving older people in the development process (Hawthorn, 2003; Keates and Clarkson, 2002), and Eisma et al. (2003) advocate the concept of ‘mutual inspiration’ to tackle this issue where close collaboration between designers and older users is started at a very early stage of any development. Gregor et al. (2002) suggest replacing the standard User Centred Design techniques which tend to rely on quite homogeneous user groups for testing, with User Sensitive Inclusive Design which seeks out diversity, in an effort to ensure true usability for older adults. Initial results from research into the effect of age when navigating in 3D scenes displayed on desktop systems points to a deterioration in performance as age increases. A negative correlation was noted, for example, between age and navigation performance in a study of the usability of collaborative desktop VEs, indicating that younger users performed better than older users (Ousland and Turcato, 1999). Dalgarno and Scott
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(2000), also found that, when evaluating motion control with 3D browsers, users younger than 40 performed slightly better than older users in movement tasks, but no further research has been done to investigate this effect more fully. This paper addresses the effect of age on the usability of visual navigation tools for navigation in 3D scenes presented on a two-dimensional desktop interface.
2. Navigation in virtual environments The concepts and technologies associated with VEs mean that designing them with a user centred approach is not as straightforward as for traditional computing applications (Herndon et al., 1994). The third dimension introduces additional issues such as user position within the environment, human-like navigation, viewpoint control and the exploratory nature of the interaction. In addition, VE users have varying objectives depending on the context of use. Users of 3D games, for instance, will have different requirements from those interacting with a multi-dimensional information visualisation space or multiple users in a collaborative virtual application. The key task of navigation, however, is common to all VE application users. Navigation is the process of moving around an environment, deciding at each step where to go (Jul and Furnas, 1997). Kaur (1998) identified navigation as the default behaviour which users return to after other interaction tasks such as the manipulation of an object. Significant usability problems, however, have been found to be caused by navigation problems (Darken et al., 1998). As a result, a large body of work exists which focuses on issues relating to 3D navigation. Several studies investigate the differences in spatial knowledge acquired from maps and exploration (Ruddle et al., 1999; Thorndyke and Hayes-Roth, 1982; Waller et al., 1998; Witmer et al., 1996). The need for landmarks to support navigation in large virtual worlds has also been emphasised (Darken and Sibert, 1996; Vinson, 1999). Further research has investigated the use of novel navigation aids such as the ‘Worlds in Miniature (WIM)’ metaphor (Stoakley et al., 1995), which provides users with a miniature representation of the loaded environment held in the virtual hand of the user and superimposed over a section of the environment itself. Both the WIM and the environment can be directly manipulated. The ‘Worldlets’ technique of Elvins et al. (1998) uses a similar approach except that there is no overlap with the presented environment— Worldlets are 3D interactive thumbnails displayed outside the environment. Chittaro and Scagnetto (2001) found ‘semitransparency’, where users are able to see through occluded surfaces within the VE, to be a useful navigation aid. 2.1. Navigation problems One of the main problems associated with navigation in VEs is the problem of becoming lost or disoriented in the virtual world. This problem has been attributed to a number of factors, including: † lack of support for speed control (Mohageg et al., 1996; Rushton and Wann, 1993). When the speed of movement is too fast, disorientation frequently occurs (Miller, 1994). Although faster speeds may reduce time and effort over large distances,
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slower velocity has been found better in carrying out precise, intricate movements (Johnsgard, 1994). Velocity, therefore, needs to be appropriate for the size of the scene presented and for the tasks which have to be carried out; navigational modes, for example ‘walking’ and ‘flying’ (Johnsgard, 1994; Tan et al., 2001). Even when in walk mode, users can become disoriented if movement is not confined to a level plane (Sayers et al., 2000); moving either too close to (Kaur et al., 1996; Marsh and Wright, 1999) or through virtual world objects (Marsh and Smith, 2000); the cognitive load placed on the navigator (Smith et al., 1999); the restricted field of view available on the screen (Neale, 1997); lack of identifiable cues (landmarks) placed within the VE itself to aid the acquisition of spatial knowledge (Darken and Sibert, 1996); support for automatic navigation (teleporting) to predefined locations within the environment (Mohageg et al., 1996). Although this has been found to be an effective means of moving to particular locations of interest within an environment, it can serve to increase a user’s sense of disorientation if further indicators of position within the environment, such as a map, are not provided (Sayers et al., 2000; Tan et al., 2001).
These problems have been shown to result in low usability and user frustration (Kaur et al., 1996; Miller, 1994). Often, much practice with a VE is required before users have gained enough familiarity with the environment to allow for successful navigation. This is a time-consuming process and users may not always be willing to take this time (Ruddle et al., 1997). The presentation of visible navigational aids on the VE interface is therefore of particular importance. This was the main finding from a usability evaluation of current 3D browser interfaces carried out by the authors (Sayers et al., 2000). Four categories of interface, differentiated by their layout, were evaluated and significant usability problems were identified. Most notably these included the issues of speed control, error correction, precise or intricate movements and the viewing plane. Many participants in the experiments found default speeds provided by the viewers to be too fast. Those interfaces which did allow for manipulation of speed had no easily identifiable control presented on the interface and users were often unaware that this facility was available, or, if they did find it, were dissatisfied with the level of control supplied. Collisions with objects within the experimental VE were frequent and rectifying the situation was often found to be very difficult. Users often used the facility to teleport to predefined locations as a means of getting out of a tricky situation, but suffered consequent disorientation. Participants frequently wanted to be able to undo particular movements yet were unable to do this. In the performance of intricate movements, such as moving around or behind an object within the environment, many difficulties were encountered. Both speed of movement and error correction were factors in this problem. Participants evidently preferred to move around the environment on a level plane as if walking in the real world and preferred to have their movement constrained to this level. As a result of these experimental findings, design recommendations were derived and applied to the development of a novel interface with visual navigation aids using the Java3D API, to enable a more thorough investigation of the usefulness of the various navigation tools presented on interfaces to 3D worlds on desktop systems.
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These recommendations and the developed interface are described in detail in Section 3 along with the design of an experiment to assess the effectiveness of the tools and the influence of age on the results. 2.2. The effect of age Two studies on Web navigation comparing older and younger users have found that older users (over 55 years and over 65 years, respectively) complete navigation tasks less successfully and more slowly than their younger counterparts (Chadwick-Diaz et al., 2003; Meyer et al., 1997). Design modifications which help older adults have been found to improve the performance of both older and younger users while not affecting the difference in performance between the two age groups (Chadwick-Diaz et al., 2003; Worden et al., 1997). A limited amount of research exists into the effect of age on navigation in VEs. Interaction in immersive VR systems has been found to be feasible for older users when using a driving simulator to assess the driving capabilities of people who have suffered head injuries (Liu et al., 1999). Ousland and Turcato (1999) identified a negative correlation between age and navigation performance in a study of the usability of desktop collaborative VEs, finding that younger users performed better than older users. Dalgarno and Scott (2000), when evaluating motion control with 3D browsers on desktop systems, found that users younger than 40 performed slightly better than older users in movement tasks. No research has been done, however, to investigate the effect of age on navigation in 3D scenes more fully.
3. Development of the experimental interface Seven design recommendations were derived from the authors’ earlier usability evaluations (Sayers et al., 2000): 1. There should be little or no hidden functionality on the interface, such as specific key presses for certain actions or having to search through a variety of menus. All tools which provide core functionality should be visible on the interface. 2. Users should easily be able to identify how to control speed of movement within an environment and also be able to flexibly control it. Although all the interfaces evaluated provided for speed control, none provided a clear indication to users of how to control speed and many users experienced frequent collisions and disorientation. 3. Since the interfaces rated most highly in the experiments provided an indication of the direction of movement, this feature should be supported. 4. Support for natural navigation modes should be supported and defined as the default movement mode. ‘Walk’ mode was the preferred means of movement in these usability experiments with movement confined to a level viewing plane so that the user’s current orientation was maintained when carrying out tasks such as turning. 5. It should be possible to reverse actions easily. An ‘undo’ facility should be supported, promoting easy error correction.
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6. A map of the VE showing the user’s position within the environment should be accessible. All participants, when asked for recommendations to improve the interfaces, suggested the provision of a map to aid orientation and wayfinding within the environment. 7. In addition to supporting automatic movement to predefined locations within a loaded environment, users should be provided with the ability to define their own locations of interest to which they can easily teleport when necessary. This was another user recommendation for improvement. Fig. 1 presents the developed interface. All core functionality is presented visibly to the user (Recommendation 1). A sliderbar allows the user to adjust the speed of movement within the displayed environment, with the default speed set to ‘walk’ (Recommendations 2 and 4). A direction dial allows the user to view the direction of movement in terms of North, South, East and West (Recommendation 3). The ‘Undo’ button allows users to undo previous actions consecutively (Recommendation 5). Fig. 2 presents the ‘you-arehere’ map superimposed on the environment in the top left-hand corner of the screen, activated by the button labelled ‘Show Map’ (Recommendation 6). This map displays the user’s current position within the environment. The user is unable to continue interaction with the displayed environment until the map is closed. A button labelled ‘Mark’ was provided in an effort to accommodate automatic navigation whilst not adversely affecting the user’s orientation (Recommendation 7). On clicking this button, a dialog box is activated which allows the user to type in his or her own choice of name for the location being labelled. This name then appears on
Fig. 1. The visible tools.
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Fig. 2. Viewing the map.
the ‘My Trail’ list at the top of the toolbar, and the user can then teleport to any of these locations automatically by double-clicking on the name (Fig. 3). The top menubar on the interface provides the facility to display each tool individually, all together (as in Fig. 1), or hide them from view completely through choices provided within the ‘View’ menu. A timer with ‘Start’, ‘Stop’, ‘Reset’ and ‘Hide’ options is also available for display from the ‘Options’ drop-down menu, in order to eliminate the need for manual timing of the experiment tasks. 3.1. Experiment design A study was designed to test the effectiveness of the tools presented within this interface and the effect of the participants’ ages on the time taken to complete navigation tasks. There were six adaptations of the interface: the control condition had no tools presented on the screen; the second, third, fourth and fifth interfaces each had an individual tool displayed along with the direction dial and list of movement modes—the map, the speed control, the mark button and the undo button, respectively; and the final condition displayed all the tools, as shown in Fig. 1. There were two age groups used within the experiment: 18–45 and 46 þ . This division was chosen for two reasons—firstly, findings from the research literature on the effect of age in desktop VE navigation point to a slight deterioration in performance at the age of 40 (Dalgarno and Scott, 2000); and secondly, due to the smaller number of older volunteers for the study, it was necessary to use this division point (45) to ensure that each of the six
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Fig. 3. Creating a user-defined location.
interface conditions contained participants from both age groups. Two hundred and four individuals (students from various faculties at the Magee Campus), aged between 18 and 68 and inexperienced in 3D navigation, volunteered as participants in this experiment, and were placed into six groups of 34—one group for each test condition (see Table 1). This betweengroups division was necessary to eliminate the learning effects due to the acquisition of navigational knowledge and experience with the navigational tools. Participants were unevenly represented in terms of both gender and age group, with 148 females (117 aged between 18 and 45, 31 aged 46 þ ) and 56 males (46 aged between 18 and 45, 10 aged 46 þ ). Due to the smaller number of male participants, especially within the smaller 46 þ age group, gender was not considered as a factor within the experimental study. All groups were asked to carry out a navigation task in a VE. The test VE used was an L-shaped ‘virtual corridor’ developed in VRML. The scene was kept as simple as possible with rooms differentiated by colour. Participants were positioned to start at the entrance to the corridor and then instructed to move into a set of six rooms consecutively within the environment in search of various objects and then finally back to the starting position. The navigation task incorporated precise, intricate movements such as entering or leaving a room or turning around and moving around and behind objects, with larger movements such as moving down the corridor. Travel inside the environment was based on an egocentric, first-person perspective ‘walk’ mode where the part of the environment which would be in front of the user’s own eyes was displayed and in which users controlled movement using the mouse. Collision detection was used to prevent users moving through objects or surfaces, and movement was confined to ‘walk’ mode.
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Table 1 The groups Group
Age group
N
Control group
18–45 46 þ Total
27 7 34
Map group
18–45 46 þ Total
27 7 34
Speed group
18–45 46 þ Total
27 7 34
Mark group
18–45 46 þ Total
27 7 34
Undo group
18–45 46 þ Total
27 7 34
All controls
18–45 46 þ Total
28 6 34
Total
18–45 46 þ Total
163 41 204
Participants were briefed at the beginning of the experiment on the functionality of whatever (if any) tools were presented. Each participant was allowed 15 min to practise navigating. Each individual was observed while carrying out the task and was encouraged to use a ‘think-aloud’ technique to record subjective comments. On completion, participants were asked to complete a usability questionnaire which consisted of a set of four statements designed to measure, using a scale of 1 – 5 (strongly disagree to strongly agree), how easy it was to navigate, whether or not participants were able to complete the tasks, how comfortable they felt using the application and how satisfied they were with the navigational aids presented. The questionnaire also gave participants the opportunity to comment on the most positive and negative aspects of their experience and to suggest how it might be improved. 3.2. Experimental hypotheses and procedure The research literature, along with our previous experimental results and observations led to the following three hypotheses: 1. The older participants would perform equally as well as the younger participants when provided with a range of navigational aids (i e. in the ‘all controls’ condition).
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Dalgarno and Scott’s (2000) study identified a slight, but not statistically significant, deterioration in navigation performance from the age of 40. With the provision of a range of navigational aids, we predict that performance differences may not be evident. 2. The groups provided with visible navigational aids, either individually or all together, would perform better and would be more satisfied with the interface than the control group. The motivation for this hypothesis was derived from the lack of an interface which provided a clearly usable range of visual tools, and the fact that participants using the interface which displayed no navigational tools in earlier experiments gave significantly lower usability ratings for the interface and even had to abandon the tasks in some cases. 3. The group presented with all the available navigational tools would perform better than the groups provided with only one navigational tool. This hypothesis is based on the assumption that different users find different navigational aids most useful—while some may become disoriented easily and find the map most useful, others may prefer to move more slowly to perform intricate movements. A two-way between-groups analysis of variance (ANOVA) was conducted. The two independent variables were the interface presented and the age group, and the dependent variable was the time taken to complete a navigation task.
4. Results Table 2 shows the means and standard deviations of the time taken to complete the navigation task for each age group across all conditions. From this descriptive data, it can be seen that the participants in both age groups obtained slower performance times when presented with the ‘control’ interface than all other conditions and obtained the best performance times when presented with all the controls. It is also noticeable that the older participants obtained worse performance times than the younger participants in every condition. The overall performance times obtained for the interfaces presenting individual navigation tools indicate that the ‘mark’ interface produced the best performance times, followed closely by the ‘undo’ interface. Examination of the results for each age group when presented with individual navigation aids show that the 46 þ age group achieved the best result using the ‘undo’ tool while the 18 –45 age group performed best using the ‘mark’ tool. Poorer performance times were obtained for both the ‘speed’ and ‘map’ interfaces. An ANOVA is the statistical procedure used to evaluate the results of an experiment with multiple groups. ANOVA is used to uncover the main and interaction effects of categorical independent variables (called ‘factors’) on a dependent variable. A ‘main effect’ is the direct effect of an independent variable on the dependent variable. An ‘interaction effect’ is the joint effect of two or more independent variables on the dependent variable. The key statistic in ANOVA is the F-test of difference of group means, testing whether the observed differences in the means of the groups (great or small) formed by values of the independent variable (or combinations of values for multiple independent variables) are the result of chance or not. If the group means do not differ
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Table 2 Age group descriptive statistics Group
Age group
Mean time (min)
Std. deviation
Control group
18–45 46 þ Total
8.21 13.06 10.49
2.77 2.44 3.56
Map group
18–45 46 þ Total
7.85 9.71 8.18
2.56 3.35 2.75
Speed group
18–45 46 þ Total
6.45 8.68 6.77
2.70 4.07 2.97
Mark group
18–45 46 þ Total
5.02 7.19 5.28
1.44 2.44 1.69
Undo group
18–45 46 þ Total
5.62 7.05 5.91
2.09 2.88 2.30
All controls
18–45 46 þ Total
4.56 5.30 4.63
1.60 2.05 1.62
Total
18–45 46 þ Total
6.12 9.87 6.88
2.54 3.89 3.22
significantly then it is inferred that the independent variable(s) did not have an effect on the dependent variable. If the F-test shows that overall the independent variable(s) is (are) related to the dependent variable, then multiple comparison tests of significance are used to explore just which value groups of the independent(s) have the most to do with the relationship. The results of the two-way ANOVA conducted show that there was a significant main effect of the interface presented on the time taken to complete the navigation tasks (Fð5; 192Þ ¼ 15:52; P , 0:001). A significant main effect was also found for age group on the dependent variable, time (Fð1; 192Þ ¼ 21:24; P , 0:001). The interface group and age group interaction, however, was not found to be statistically significant (Fð5; 192Þ ¼ 1:483; P ¼ 0:197), indicating that the effect of the interface presented was not different for the two age groups. Both age groups performed similarly in all variations of interface group. An ANOVA tests for an overall experimental effect but does not provide specific information about which groups were affected. To obtain this additional information, it is necessary to perform some comparisons using contrasts. Two standard contrasts were conducted: the first comparing all groups with the control group (‘no controls’); and the second comparing all groups with the group presenting all the visual tools (‘all controls’).
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The results from the first simple contrast show that there were significant statistical differences ðP , 0:05Þ in the time taken to complete the navigation tasks between each of the groups displaying tools (map, speed, mark, undo and all controls) and the control group with no navigation aids. In the case of the second simple contrast, where every group was compared with the final group (all controls), a significant statistical difference ðP , 0:05Þ was found with the ‘no controls’, ‘map’ and ‘speed’ groups, but no significant difference was found between the ‘all controls’ group and the ‘mark’ (P ¼ 0:165) and ‘undo’ groups (P ¼ 0:83). This suggests that these particular visual navigation aids were found to be particularly useful, producing performance times relatively close to those achieved by the ‘all controls’ group. Tukey’s HSD, the Bonferroni and Games-Howell post hoc procedures were carried out to compare each group of subjects with each other. Tukey’s HSD and the Bonferroni post hoc tests both control the type 1 error rate well (the probability of falsely rejecting the null hypothesis), while the Games-Howell post hoc procedure deals well with population variances (Field, 2000). Results from these tests confirm that, for each group, there was a significant statistical difference between the ‘control’ group and all the others, as well as between the ‘all controls’ group and the ‘control’, ‘map’ and ‘speed’ groups (P , 0:05). No significant differences were found between the ‘speed’ group and the ‘map’, ‘mark’ and ‘undo’ groups, respectively, or between the ‘mark’ group and the ‘speed’, ‘undo’ and ‘all controls’ groups, respectively. Significant differences were found, however, when comparing both the ‘mark’ group and the ‘undo’ group with the ‘map’ group. These results indicate that the ‘mark’ and ‘undo’ tools were the most useful in helping decrease navigation time. 4.1. Usability results Figs. 4 – 7 display the ratings for each of the four statements presented on the postexperimental usability questionnaire. Subjective ratings from 1 to 5, based on Nielsen’s attributes of usability (Nielsen, 1993), were used to represent ‘strongly disagree’ through to ‘strongly agree’, respectively: Statement 1. Overall, I am satisfied with how easy it is to navigate using this interface. Statement 2. I was able to complete the tasks successfully. Statement 3. The interface has all the functions and capabilities I would expect it to have. Statement 4. Overall, I am satisfied with the tools presented on the screen. The usability scores for Statements 1, 3 and 4 (Figs. 4, 6 and 7) show a similar trend to the performance time results in that, for both age groups, the ‘control group’ was rated lower than the interfaces displaying navigational aids. Fig. 5 (Statement 2) shows that participants were generally able to complete the navigation task using all six interface conditions—there was only one participant from the 46 þ age group was unable to complete the navigation task when using the ‘control’ interface. It is noticeable from Figs. 4 – 7 that younger participants scored the ‘control group’ higher than their older counterparts in all four cases, suggesting that they
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Fig. 4. Ease of navigation ratings.
were less daunted by carrying out the navigation task without navigational support presented on the interface. Younger participants rated the ‘mark’ tool very highly in terms of ease of navigation (Fig. 4) and in relation to overall satisfaction with the interface (Fig. 7). Considering observations made during the experiments themselves, the results from the questionnaire were sometimes surprising since there was often no correlation between what was observed and the ratings given. From observation, for example, it
Fig. 5. Usability ratings—ability to complete tasks.
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Fig. 6. Usability ratings—expected functionality.
was obvious that many younger participants in the ‘control group’ experienced a high degree of frustration with the application, yet they often did not reflect this in the ratings given. These anomalies may be explained by factors such as the novelty of the 3D navigation, not understanding or having adequate knowledge about the statements presented, or ‘politeness’ since they were being observed.
Fig. 7. Usability ratings—satisfaction.
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5. Discussion Since significant differences were found between the two age groups used in this experiment, hypothesis 1 has not been supported by these experimental findings: provision of a combination of navigational aids does not eliminate the age differences. The slight deterioration identified by Dalgarno and Scott (2000) in navigation performance from the age of 40 may therefore perhaps be attributable to the age factor. It is noticeable, however, how performance times improved for older participants when they were presented with a variety of tools (in the ‘all controls’ interface condition). In this condition, the least difference in performance times between the two age groups was recorded with younger participants achieving an average time of 4 min, 56 s and older participants achieving an average time of 5 min, 30 s (see Table 2). Further work is necessary to investigate if this difference can be reduced or eliminated with further navigational support. The second hypothesis is supported by the results of the first simple contrast. There were statistically significant differences found between the performance times obtained for the ‘control’ group and each of the other interface conditions. The usability results also confirm this finding in that lower ratings were consistently awarded for the ‘control’ group and it was the only condition where a participant was unable to complete the set task. These findings support the authors’ earlier experimental conclusions (Sayers et al., 2000), emphasizing the need for the visual display of navigational aids on a two-dimensional interface. This conclusion can be applied to users of all ages. Hypothesis 3 predicts improved performance when a variety of navigation aids are provided rather than a single aid and is partly supported by the findings from this study. The interface displaying all the tools (‘all controls’) did produce statistically significant navigation times when compared with the interfaces displaying a map function and a speed function, respectively. There was no significant difference found, however, between this group and the ‘mark’ or ‘undo’ groups. This result indicates that these two tools (‘mark’ and ‘undo’) were found particularly useful for navigation and this is supported by observation of the participants, the ‘think-aloud’ technique employed, and the usability ratings scored. From observation and comments it was clear that the ‘mark’ tool was frequently used as a means of error correction—participants in both age groups used it to index useful viewpoints within the environment, to which they then teleported when encountering difficulty with the navigation task. The high usability ratings received for the ‘mark’ and ‘undo’ tools, when combined with the fact that there was no significant difference found between their performance times and that of the ‘all controls’ condition, point to the importance of effective error correction in the navigation process. The map tool was not found particularly useful in this experiment yet this finding needs to be treated with caution due to the small size of the VE presented. From observation of the participants, it was noticeable that the map was used infrequently and participants often stated that they found that they were not lost within the environment and did not need to use the tool. Earlier studies by Ruddle et al. (1999) show the usefulness of maps for navigation in very-large-scale VEs, so we can only conclude that a map might not be a particularly useful navigational aid in small VEs.
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6. Conclusions and future work This paper has presented the results of an experiment designed to investigate the effect of various interface tools and age on navigation performance times and user satisfaction. From the results presented, we can say that age has a significant effect on 3D navigation using desktop systems, with younger users consistently outperforming their older counterparts. As the user community for these types of applications broadens, age must be considered as an element in the design process, and the decrease in time differences between the two age groups when presented with a variety of tools suggests that further research into what factors might reduce (or eliminate) this gap are necessary. A study by Emery et al. (2003) suggests that multimodal interaction may be the way forward when designing for the next generation of older people who will be more familiar with computer technology as it continues to integrate every aspect of modern everyday life. Emery et al. (2003) found that the performance of older adults (aged 65 þ ) with varying levels of computing experience, was improved when using a Graphical User Interface with the use of some form of multimodal feedback (visual, auditory, haptic) as opposed to input, and that this was more noticeable the higher the level of computing experience. We can also conclude that the inclusion of visibly presented navigation aids has a significant beneficial effect on navigation performance times for all ages, resulting in better levels of user satisfaction. In addition, the abilities to mark user-defined locations within an environment, and to undo actions were found to produce the fastest performance times and to be the most highly rated individual tools. Further work involving large-scale VEs is needed to thoroughly test the effectiveness of individual tools such as the map and speed control facilities presented in this study.
References Browne, H., 2000. Accessibility and Usability of Information Technology by the Elderly, http://www.otal.umd. edu/UUGuide/hbrowne/. Chadwick-Diaz, A., McNulty, M., Tullis, T., 2003. Web usability and age: how design changes can improve performance, Proceedings of the 2003 ACM Conference on Universal Usability (CUU03), pp. 30– 37. Chittaro, L., Scagnetto, I., 2001. Is semitransparency useful for navigating virtual environments? VRST01: Eighth ACM Symposium on Virtual Reality Software and Technology, Canada, pp. 159–166. Czaja, S.J., 1996. Aging and the acquisition of computer skills. In: Rogers, W.A., Fisk, A.D., Walker, N. (Eds.), Aging and Skilled Performance. Lawrence Erlbaum, London, pp. 201 –220. Dalgarno, B., Scott, J., 2000. Motion control in virtual environments: a comparative study. In: Paelke, V., Volbracht, S. (Eds.), User Guidance in Virtual Environments, Proceedings of the Workshop on Guiding Users through Interactive Experiences: Usability Centred Design and Evaluation of Virtual 3D Environments, 13– 14 April, pp. 111 –122. Darken, R., Sibert, J.L., 1996. Navigating large virtual worlds. The International Journal of Human–Computer Interaction 8(1), 49 –72. Darken, R., Allard, T., Achille, L., 1998. Spatial orientation and wayfinding in large-scale virtual spaces. Presence 7(2), 101 –107. Eisma, R., Dickinson, A., Goodman, J., Mival, O., Syme, A., Tiwari, L., 2003. Mutual inspiration in the development of new technology for older people, Proceedings of Include 2003, Inclusive Design for Society and Business, Royal College of Art, London, 25–28 March, http://www.computing.dundee.ac.uk/projects/ UTOPIA/publications/Include2003Eisma.doc.
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Nielsen, J., 1993. Usability Engineering. Academic Press, London. Ousland, A.R., Turcato, H., 1999. Navigating 3D Environments, EURESCOM, European Institute for Research and Strategic Studies in Telecommunications, Project P807, JUPITER2—Joint Usability, Performability and Interoperability Trials in Europe, http://www.eurescom.de/~publicwebspace/P800series/P807/results/ Usability/R3/D2-T3-Usability-R3-Navigating3D.pdf. Rogers, W.A., 1997. Individual differences, aging, and human factors: an overview. In: Fisk, A.D., Rogers, W.A. (Eds.), Handbook of Human Factors and the Older Adult. Academic Press, London, pp. 151– 170. Ruddle, R.A., Payne, S.J., Jones, D.M., 1997. Navigating buildings in desk-top virtual environments: experimental investigations using extended navigational experience. Journal of Experimental Psychology: Applied 3(2), 143–159. Ruddle, R.A., Payne, S.J., Jones, D.M., 1999. The effects of maps on navigation and search strategies in verylarge-scale virtual environments. Journal of Experimental Psychology: Applied 5(1), 54 –75. Rushton, S., Wann, J., 1993. Problems in perception and action in virtual worlds, IEEE Virtual Reality International Symposium, Seattle, Washington, pp. 43– 55. Sayers, H.M., Wilson, S., McNeill, M.D.J., Scott, T.M., 1999. Usability issues in collaborative virtual office applications. Proceedings of the Sixth Annual UKVRSIG Conference, Salford University, 14th September 1999, 119 –131. Sayers, H.M., Wilson, S., Myles, W., McNeill, M.D.J., 2000. Usable interfaces for virtual environment applications on non-immersive systems, Proceedings of the 18th Annual Eurographics UK Conference, Swansea, 4–6 April, pp. 143 –151. Smith, S., Duke, D., Wright, P., 1999. Using the resources model in virtual environment design. User Centered Design and Implementation of Virtual Environments, Workshop at King’s Manor, University of York, 30th September 1999, 57– 73. Stoakley, R., Conway, M.J., Pausch, R., 1995. Virtual reality on a WIM: interactive worlds in miniature, Proceedings of CHI’95, 7 –11 May, ACM Press, Denver, Colorado. pp. 265–272. Tan, D.S., Robertson, G.G., Czerwinski, M., 2001. Exploring 3D navigation: combining speed-coupled flying with orbiting. Proceedings of CHI 2001 on Human Factors in Computing Systems 3(1), 418– 425. Thorndyke, P.W., Hayes-Roth, B., 1982. Differences in spatial knowledge acquired from maps and navigation. Cognitive Psychology 14, 560–589. Vinson, N.G., 1999. Design guidelines for landmarks to support navigation in virtual environments, Proceedings of CHI’99. ACM Press, Pittsburgh, PA. Waller, D., Hunt, E., Knapp, D., 1998. The transfer of spatial knowledge in virtual environment training. Presence: Teleoperators and Virtual Environments 7(2), 129 –143. Witmer, B., Bailey, J., Knerr, B., Parsons, K., 1996. Virtual spaces and real world places: transfer of route knowledge. International Journal of Human–Computer Studies 45, 413 –428. Worden, A., Walker, N., Bharat, K., Hudson, S., 1997. Making computers easier for older adults to use: area cursors and sticky icons, Proceedings of Human Factors in Computing Systems (CHI’97), Atlanta, pp. 266-271. Zajicek, M., 2003. Patterns for encapsulating speech interface design solutions for older adults, Proceedings of the 2003 ACM Conference on Universal Usability (CUU03), 10–11 November, Vancouver, Canada, pp. 54 –60.
Desktop virtual environments: a study of navigation and age H. Sayers* School of Computing and Intelligent Systems, University of Ulster, Magee Campus, Londonderry BT48 7JL, UK Received 6 February 2004; revised 4 May 2004; accepted 13 May 2004 Available online 2 July 2004
Abstract Navigation in virtual environments on desktop systems is known to be problematic. Research into the usability of the tools presented on two-dimensional interfaces indicates that, for even relatively simple tasks, users experience some degree of frustration. As the user community broadens with an increasing range of applications and services making use of three-dimensional presentation, the usability of these interfaces becomes ever more important. In this paper, we describe the results of an experiment performed to evaluate the usability of a number of visual navigation tools and the effect for two age groups (18– 45 and 46 þ ). Results indicate that, for both age groups, the visual presentation of navigational aids improves navigation performance in terms of both time taken to complete tasks, and user satisfaction with the system. In all experimental conditions younger participants achieved better performance times, although the gap between the groups decreased when a choice of navigation aids was presented. q 2004 Elsevier B.V. All rights reserved. Keywords: Desktop virtual environments; Navigation; Age; Usability
1. Introduction A three-dimensional (3D) virtual environment (VE) is a computer representation of a real world space or an imaginary space through which users can navigate and in which they can interact with objects. Unlike fully immersive VEs which use specialised interaction devices such as head-mounted displays to create a sense of presence for the user within the 3D world, desktop systems exploit general-purpose hardware for interaction (PC, mouse, keyboard) and although obviously offer a much reduced sense of * Tel.: þ44-28-71375553; fax: þ44-28-71375470. E-mail address: [email protected] 0953-5438/$ - see front matter q 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.intcom.2004.05.003
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presence in the VE, are still useful for many application areas (Green and Jacob, 1991). The Virtual Reality Modeling Language (VRML), commonly supported by all popular Internet browsers, has opened up VE technology to a wide range of users using standard desktop systems. Research has shown that existing user interface guidelines do not address the particular requirements for interfaces to VEs, and no standard ‘look and feel’ has yet evolved for interfaces to 3D worlds (Hand, 1997). Users of VE applications, however, require intuitive tools to maximise their productivity. In VE applications, this need can be defined as the need for effective navigation and interaction. There has been much research into usability design for virtual environments themselves (Fencott, 1999; Kaur, 1998; Kaur Deol et al., 1999; Sayers et al., 1999), but little consideration has been given to the usability of the tools presented on interfaces to desktop VEs. There has also been little research into the effect of age on the usability of such tools. The population of the developed world is getting older, and the use of computers in everyday life is becoming more prevalent and indeed more necessary. In order to avoid social exclusion and to be able to live more independently, therefore, older adults will increasingly need to be able to use computers and computer systems (Zajicek, 2003). Hawthorn (2000) reports that in the United States, people over 45 years old will soon constitute over half of the adult population. Research has shown that older users (over 60 years), although willing to learn to use computers, consistently have more difficulty than younger people (Czaja, 1996). As older users become increasingly exposed to computer technology, understanding their unique requirements will become a much more important consideration in the design of human–computer interfaces than at present, and a body of research has begun to focus on human–computer interface design to assist interaction with two-dimensional applications for older users (Czaja, 1996; Mead et al., 1997; Worden et al., 1997). Hawthorn (2003) highlights the perceived changes in future older generations and computer experience (i.e. that the number of inexperienced older users will decrease) and believes that there is a very interesting and important research topic to be found in how today’s 40–60-year-old computer users will adapt to changes in computing technology as they get older. Older people are as diverse as younger people. Their exposure to computers, for example, will vary, with many having had little or none, while younger people have grown up with technology as an integral part of their lives. Changes in older adults’ abilities— physical and cognitive—also vary considerably (Rogers, 1997). A one-size-fits-all design approach is therefore inappropriate for this user group (Browne, 2000). Research has acknowledged the importance of involving older people in the development process (Hawthorn, 2003; Keates and Clarkson, 2002), and Eisma et al. (2003) advocate the concept of ‘mutual inspiration’ to tackle this issue where close collaboration between designers and older users is started at a very early stage of any development. Gregor et al. (2002) suggest replacing the standard User Centred Design techniques which tend to rely on quite homogeneous user groups for testing, with User Sensitive Inclusive Design which seeks out diversity, in an effort to ensure true usability for older adults. Initial results from research into the effect of age when navigating in 3D scenes displayed on desktop systems points to a deterioration in performance as age increases. A negative correlation was noted, for example, between age and navigation performance in a study of the usability of collaborative desktop VEs, indicating that younger users performed better than older users (Ousland and Turcato, 1999). Dalgarno and Scott
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(2000), also found that, when evaluating motion control with 3D browsers, users younger than 40 performed slightly better than older users in movement tasks, but no further research has been done to investigate this effect more fully. This paper addresses the effect of age on the usability of visual navigation tools for navigation in 3D scenes presented on a two-dimensional desktop interface.
2. Navigation in virtual environments The concepts and technologies associated with VEs mean that designing them with a user centred approach is not as straightforward as for traditional computing applications (Herndon et al., 1994). The third dimension introduces additional issues such as user position within the environment, human-like navigation, viewpoint control and the exploratory nature of the interaction. In addition, VE users have varying objectives depending on the context of use. Users of 3D games, for instance, will have different requirements from those interacting with a multi-dimensional information visualisation space or multiple users in a collaborative virtual application. The key task of navigation, however, is common to all VE application users. Navigation is the process of moving around an environment, deciding at each step where to go (Jul and Furnas, 1997). Kaur (1998) identified navigation as the default behaviour which users return to after other interaction tasks such as the manipulation of an object. Significant usability problems, however, have been found to be caused by navigation problems (Darken et al., 1998). As a result, a large body of work exists which focuses on issues relating to 3D navigation. Several studies investigate the differences in spatial knowledge acquired from maps and exploration (Ruddle et al., 1999; Thorndyke and Hayes-Roth, 1982; Waller et al., 1998; Witmer et al., 1996). The need for landmarks to support navigation in large virtual worlds has also been emphasised (Darken and Sibert, 1996; Vinson, 1999). Further research has investigated the use of novel navigation aids such as the ‘Worlds in Miniature (WIM)’ metaphor (Stoakley et al., 1995), which provides users with a miniature representation of the loaded environment held in the virtual hand of the user and superimposed over a section of the environment itself. Both the WIM and the environment can be directly manipulated. The ‘Worldlets’ technique of Elvins et al. (1998) uses a similar approach except that there is no overlap with the presented environment— Worldlets are 3D interactive thumbnails displayed outside the environment. Chittaro and Scagnetto (2001) found ‘semitransparency’, where users are able to see through occluded surfaces within the VE, to be a useful navigation aid. 2.1. Navigation problems One of the main problems associated with navigation in VEs is the problem of becoming lost or disoriented in the virtual world. This problem has been attributed to a number of factors, including: † lack of support for speed control (Mohageg et al., 1996; Rushton and Wann, 1993). When the speed of movement is too fast, disorientation frequently occurs (Miller, 1994). Although faster speeds may reduce time and effort over large distances,
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slower velocity has been found better in carrying out precise, intricate movements (Johnsgard, 1994). Velocity, therefore, needs to be appropriate for the size of the scene presented and for the tasks which have to be carried out; navigational modes, for example ‘walking’ and ‘flying’ (Johnsgard, 1994; Tan et al., 2001). Even when in walk mode, users can become disoriented if movement is not confined to a level plane (Sayers et al., 2000); moving either too close to (Kaur et al., 1996; Marsh and Wright, 1999) or through virtual world objects (Marsh and Smith, 2000); the cognitive load placed on the navigator (Smith et al., 1999); the restricted field of view available on the screen (Neale, 1997); lack of identifiable cues (landmarks) placed within the VE itself to aid the acquisition of spatial knowledge (Darken and Sibert, 1996); support for automatic navigation (teleporting) to predefined locations within the environment (Mohageg et al., 1996). Although this has been found to be an effective means of moving to particular locations of interest within an environment, it can serve to increase a user’s sense of disorientation if further indicators of position within the environment, such as a map, are not provided (Sayers et al., 2000; Tan et al., 2001).
These problems have been shown to result in low usability and user frustration (Kaur et al., 1996; Miller, 1994). Often, much practice with a VE is required before users have gained enough familiarity with the environment to allow for successful navigation. This is a time-consuming process and users may not always be willing to take this time (Ruddle et al., 1997). The presentation of visible navigational aids on the VE interface is therefore of particular importance. This was the main finding from a usability evaluation of current 3D browser interfaces carried out by the authors (Sayers et al., 2000). Four categories of interface, differentiated by their layout, were evaluated and significant usability problems were identified. Most notably these included the issues of speed control, error correction, precise or intricate movements and the viewing plane. Many participants in the experiments found default speeds provided by the viewers to be too fast. Those interfaces which did allow for manipulation of speed had no easily identifiable control presented on the interface and users were often unaware that this facility was available, or, if they did find it, were dissatisfied with the level of control supplied. Collisions with objects within the experimental VE were frequent and rectifying the situation was often found to be very difficult. Users often used the facility to teleport to predefined locations as a means of getting out of a tricky situation, but suffered consequent disorientation. Participants frequently wanted to be able to undo particular movements yet were unable to do this. In the performance of intricate movements, such as moving around or behind an object within the environment, many difficulties were encountered. Both speed of movement and error correction were factors in this problem. Participants evidently preferred to move around the environment on a level plane as if walking in the real world and preferred to have their movement constrained to this level. As a result of these experimental findings, design recommendations were derived and applied to the development of a novel interface with visual navigation aids using the Java3D API, to enable a more thorough investigation of the usefulness of the various navigation tools presented on interfaces to 3D worlds on desktop systems.
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These recommendations and the developed interface are described in detail in Section 3 along with the design of an experiment to assess the effectiveness of the tools and the influence of age on the results. 2.2. The effect of age Two studies on Web navigation comparing older and younger users have found that older users (over 55 years and over 65 years, respectively) complete navigation tasks less successfully and more slowly than their younger counterparts (Chadwick-Diaz et al., 2003; Meyer et al., 1997). Design modifications which help older adults have been found to improve the performance of both older and younger users while not affecting the difference in performance between the two age groups (Chadwick-Diaz et al., 2003; Worden et al., 1997). A limited amount of research exists into the effect of age on navigation in VEs. Interaction in immersive VR systems has been found to be feasible for older users when using a driving simulator to assess the driving capabilities of people who have suffered head injuries (Liu et al., 1999). Ousland and Turcato (1999) identified a negative correlation between age and navigation performance in a study of the usability of desktop collaborative VEs, finding that younger users performed better than older users. Dalgarno and Scott (2000), when evaluating motion control with 3D browsers on desktop systems, found that users younger than 40 performed slightly better than older users in movement tasks. No research has been done, however, to investigate the effect of age on navigation in 3D scenes more fully.
3. Development of the experimental interface Seven design recommendations were derived from the authors’ earlier usability evaluations (Sayers et al., 2000): 1. There should be little or no hidden functionality on the interface, such as specific key presses for certain actions or having to search through a variety of menus. All tools which provide core functionality should be visible on the interface. 2. Users should easily be able to identify how to control speed of movement within an environment and also be able to flexibly control it. Although all the interfaces evaluated provided for speed control, none provided a clear indication to users of how to control speed and many users experienced frequent collisions and disorientation. 3. Since the interfaces rated most highly in the experiments provided an indication of the direction of movement, this feature should be supported. 4. Support for natural navigation modes should be supported and defined as the default movement mode. ‘Walk’ mode was the preferred means of movement in these usability experiments with movement confined to a level viewing plane so that the user’s current orientation was maintained when carrying out tasks such as turning. 5. It should be possible to reverse actions easily. An ‘undo’ facility should be supported, promoting easy error correction.
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6. A map of the VE showing the user’s position within the environment should be accessible. All participants, when asked for recommendations to improve the interfaces, suggested the provision of a map to aid orientation and wayfinding within the environment. 7. In addition to supporting automatic movement to predefined locations within a loaded environment, users should be provided with the ability to define their own locations of interest to which they can easily teleport when necessary. This was another user recommendation for improvement. Fig. 1 presents the developed interface. All core functionality is presented visibly to the user (Recommendation 1). A sliderbar allows the user to adjust the speed of movement within the displayed environment, with the default speed set to ‘walk’ (Recommendations 2 and 4). A direction dial allows the user to view the direction of movement in terms of North, South, East and West (Recommendation 3). The ‘Undo’ button allows users to undo previous actions consecutively (Recommendation 5). Fig. 2 presents the ‘you-arehere’ map superimposed on the environment in the top left-hand corner of the screen, activated by the button labelled ‘Show Map’ (Recommendation 6). This map displays the user’s current position within the environment. The user is unable to continue interaction with the displayed environment until the map is closed. A button labelled ‘Mark’ was provided in an effort to accommodate automatic navigation whilst not adversely affecting the user’s orientation (Recommendation 7). On clicking this button, a dialog box is activated which allows the user to type in his or her own choice of name for the location being labelled. This name then appears on
Fig. 1. The visible tools.
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Fig. 2. Viewing the map.
the ‘My Trail’ list at the top of the toolbar, and the user can then teleport to any of these locations automatically by double-clicking on the name (Fig. 3). The top menubar on the interface provides the facility to display each tool individually, all together (as in Fig. 1), or hide them from view completely through choices provided within the ‘View’ menu. A timer with ‘Start’, ‘Stop’, ‘Reset’ and ‘Hide’ options is also available for display from the ‘Options’ drop-down menu, in order to eliminate the need for manual timing of the experiment tasks. 3.1. Experiment design A study was designed to test the effectiveness of the tools presented within this interface and the effect of the participants’ ages on the time taken to complete navigation tasks. There were six adaptations of the interface: the control condition had no tools presented on the screen; the second, third, fourth and fifth interfaces each had an individual tool displayed along with the direction dial and list of movement modes—the map, the speed control, the mark button and the undo button, respectively; and the final condition displayed all the tools, as shown in Fig. 1. There were two age groups used within the experiment: 18–45 and 46 þ . This division was chosen for two reasons—firstly, findings from the research literature on the effect of age in desktop VE navigation point to a slight deterioration in performance at the age of 40 (Dalgarno and Scott, 2000); and secondly, due to the smaller number of older volunteers for the study, it was necessary to use this division point (45) to ensure that each of the six
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Fig. 3. Creating a user-defined location.
interface conditions contained participants from both age groups. Two hundred and four individuals (students from various faculties at the Magee Campus), aged between 18 and 68 and inexperienced in 3D navigation, volunteered as participants in this experiment, and were placed into six groups of 34—one group for each test condition (see Table 1). This betweengroups division was necessary to eliminate the learning effects due to the acquisition of navigational knowledge and experience with the navigational tools. Participants were unevenly represented in terms of both gender and age group, with 148 females (117 aged between 18 and 45, 31 aged 46 þ ) and 56 males (46 aged between 18 and 45, 10 aged 46 þ ). Due to the smaller number of male participants, especially within the smaller 46 þ age group, gender was not considered as a factor within the experimental study. All groups were asked to carry out a navigation task in a VE. The test VE used was an L-shaped ‘virtual corridor’ developed in VRML. The scene was kept as simple as possible with rooms differentiated by colour. Participants were positioned to start at the entrance to the corridor and then instructed to move into a set of six rooms consecutively within the environment in search of various objects and then finally back to the starting position. The navigation task incorporated precise, intricate movements such as entering or leaving a room or turning around and moving around and behind objects, with larger movements such as moving down the corridor. Travel inside the environment was based on an egocentric, first-person perspective ‘walk’ mode where the part of the environment which would be in front of the user’s own eyes was displayed and in which users controlled movement using the mouse. Collision detection was used to prevent users moving through objects or surfaces, and movement was confined to ‘walk’ mode.
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Table 1 The groups Group
Age group
N
Control group
18–45 46 þ Total
27 7 34
Map group
18–45 46 þ Total
27 7 34
Speed group
18–45 46 þ Total
27 7 34
Mark group
18–45 46 þ Total
27 7 34
Undo group
18–45 46 þ Total
27 7 34
All controls
18–45 46 þ Total
28 6 34
Total
18–45 46 þ Total
163 41 204
Participants were briefed at the beginning of the experiment on the functionality of whatever (if any) tools were presented. Each participant was allowed 15 min to practise navigating. Each individual was observed while carrying out the task and was encouraged to use a ‘think-aloud’ technique to record subjective comments. On completion, participants were asked to complete a usability questionnaire which consisted of a set of four statements designed to measure, using a scale of 1 – 5 (strongly disagree to strongly agree), how easy it was to navigate, whether or not participants were able to complete the tasks, how comfortable they felt using the application and how satisfied they were with the navigational aids presented. The questionnaire also gave participants the opportunity to comment on the most positive and negative aspects of their experience and to suggest how it might be improved. 3.2. Experimental hypotheses and procedure The research literature, along with our previous experimental results and observations led to the following three hypotheses: 1. The older participants would perform equally as well as the younger participants when provided with a range of navigational aids (i e. in the ‘all controls’ condition).
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Dalgarno and Scott’s (2000) study identified a slight, but not statistically significant, deterioration in navigation performance from the age of 40. With the provision of a range of navigational aids, we predict that performance differences may not be evident. 2. The groups provided with visible navigational aids, either individually or all together, would perform better and would be more satisfied with the interface than the control group. The motivation for this hypothesis was derived from the lack of an interface which provided a clearly usable range of visual tools, and the fact that participants using the interface which displayed no navigational tools in earlier experiments gave significantly lower usability ratings for the interface and even had to abandon the tasks in some cases. 3. The group presented with all the available navigational tools would perform better than the groups provided with only one navigational tool. This hypothesis is based on the assumption that different users find different navigational aids most useful—while some may become disoriented easily and find the map most useful, others may prefer to move more slowly to perform intricate movements. A two-way between-groups analysis of variance (ANOVA) was conducted. The two independent variables were the interface presented and the age group, and the dependent variable was the time taken to complete a navigation task.
4. Results Table 2 shows the means and standard deviations of the time taken to complete the navigation task for each age group across all conditions. From this descriptive data, it can be seen that the participants in both age groups obtained slower performance times when presented with the ‘control’ interface than all other conditions and obtained the best performance times when presented with all the controls. It is also noticeable that the older participants obtained worse performance times than the younger participants in every condition. The overall performance times obtained for the interfaces presenting individual navigation tools indicate that the ‘mark’ interface produced the best performance times, followed closely by the ‘undo’ interface. Examination of the results for each age group when presented with individual navigation aids show that the 46 þ age group achieved the best result using the ‘undo’ tool while the 18 –45 age group performed best using the ‘mark’ tool. Poorer performance times were obtained for both the ‘speed’ and ‘map’ interfaces. An ANOVA is the statistical procedure used to evaluate the results of an experiment with multiple groups. ANOVA is used to uncover the main and interaction effects of categorical independent variables (called ‘factors’) on a dependent variable. A ‘main effect’ is the direct effect of an independent variable on the dependent variable. An ‘interaction effect’ is the joint effect of two or more independent variables on the dependent variable. The key statistic in ANOVA is the F-test of difference of group means, testing whether the observed differences in the means of the groups (great or small) formed by values of the independent variable (or combinations of values for multiple independent variables) are the result of chance or not. If the group means do not differ
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Table 2 Age group descriptive statistics Group
Age group
Mean time (min)
Std. deviation
Control group
18–45 46 þ Total
8.21 13.06 10.49
2.77 2.44 3.56
Map group
18–45 46 þ Total
7.85 9.71 8.18
2.56 3.35 2.75
Speed group
18–45 46 þ Total
6.45 8.68 6.77
2.70 4.07 2.97
Mark group
18–45 46 þ Total
5.02 7.19 5.28
1.44 2.44 1.69
Undo group
18–45 46 þ Total
5.62 7.05 5.91
2.09 2.88 2.30
All controls
18–45 46 þ Total
4.56 5.30 4.63
1.60 2.05 1.62
Total
18–45 46 þ Total
6.12 9.87 6.88
2.54 3.89 3.22
significantly then it is inferred that the independent variable(s) did not have an effect on the dependent variable. If the F-test shows that overall the independent variable(s) is (are) related to the dependent variable, then multiple comparison tests of significance are used to explore just which value groups of the independent(s) have the most to do with the relationship. The results of the two-way ANOVA conducted show that there was a significant main effect of the interface presented on the time taken to complete the navigation tasks (Fð5; 192Þ ¼ 15:52; P , 0:001). A significant main effect was also found for age group on the dependent variable, time (Fð1; 192Þ ¼ 21:24; P , 0:001). The interface group and age group interaction, however, was not found to be statistically significant (Fð5; 192Þ ¼ 1:483; P ¼ 0:197), indicating that the effect of the interface presented was not different for the two age groups. Both age groups performed similarly in all variations of interface group. An ANOVA tests for an overall experimental effect but does not provide specific information about which groups were affected. To obtain this additional information, it is necessary to perform some comparisons using contrasts. Two standard contrasts were conducted: the first comparing all groups with the control group (‘no controls’); and the second comparing all groups with the group presenting all the visual tools (‘all controls’).
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The results from the first simple contrast show that there were significant statistical differences ðP , 0:05Þ in the time taken to complete the navigation tasks between each of the groups displaying tools (map, speed, mark, undo and all controls) and the control group with no navigation aids. In the case of the second simple contrast, where every group was compared with the final group (all controls), a significant statistical difference ðP , 0:05Þ was found with the ‘no controls’, ‘map’ and ‘speed’ groups, but no significant difference was found between the ‘all controls’ group and the ‘mark’ (P ¼ 0:165) and ‘undo’ groups (P ¼ 0:83). This suggests that these particular visual navigation aids were found to be particularly useful, producing performance times relatively close to those achieved by the ‘all controls’ group. Tukey’s HSD, the Bonferroni and Games-Howell post hoc procedures were carried out to compare each group of subjects with each other. Tukey’s HSD and the Bonferroni post hoc tests both control the type 1 error rate well (the probability of falsely rejecting the null hypothesis), while the Games-Howell post hoc procedure deals well with population variances (Field, 2000). Results from these tests confirm that, for each group, there was a significant statistical difference between the ‘control’ group and all the others, as well as between the ‘all controls’ group and the ‘control’, ‘map’ and ‘speed’ groups (P , 0:05). No significant differences were found between the ‘speed’ group and the ‘map’, ‘mark’ and ‘undo’ groups, respectively, or between the ‘mark’ group and the ‘speed’, ‘undo’ and ‘all controls’ groups, respectively. Significant differences were found, however, when comparing both the ‘mark’ group and the ‘undo’ group with the ‘map’ group. These results indicate that the ‘mark’ and ‘undo’ tools were the most useful in helping decrease navigation time. 4.1. Usability results Figs. 4 – 7 display the ratings for each of the four statements presented on the postexperimental usability questionnaire. Subjective ratings from 1 to 5, based on Nielsen’s attributes of usability (Nielsen, 1993), were used to represent ‘strongly disagree’ through to ‘strongly agree’, respectively: Statement 1. Overall, I am satisfied with how easy it is to navigate using this interface. Statement 2. I was able to complete the tasks successfully. Statement 3. The interface has all the functions and capabilities I would expect it to have. Statement 4. Overall, I am satisfied with the tools presented on the screen. The usability scores for Statements 1, 3 and 4 (Figs. 4, 6 and 7) show a similar trend to the performance time results in that, for both age groups, the ‘control group’ was rated lower than the interfaces displaying navigational aids. Fig. 5 (Statement 2) shows that participants were generally able to complete the navigation task using all six interface conditions—there was only one participant from the 46 þ age group was unable to complete the navigation task when using the ‘control’ interface. It is noticeable from Figs. 4 – 7 that younger participants scored the ‘control group’ higher than their older counterparts in all four cases, suggesting that they
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Fig. 4. Ease of navigation ratings.
were less daunted by carrying out the navigation task without navigational support presented on the interface. Younger participants rated the ‘mark’ tool very highly in terms of ease of navigation (Fig. 4) and in relation to overall satisfaction with the interface (Fig. 7). Considering observations made during the experiments themselves, the results from the questionnaire were sometimes surprising since there was often no correlation between what was observed and the ratings given. From observation, for example, it
Fig. 5. Usability ratings—ability to complete tasks.
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Fig. 6. Usability ratings—expected functionality.
was obvious that many younger participants in the ‘control group’ experienced a high degree of frustration with the application, yet they often did not reflect this in the ratings given. These anomalies may be explained by factors such as the novelty of the 3D navigation, not understanding or having adequate knowledge about the statements presented, or ‘politeness’ since they were being observed.
Fig. 7. Usability ratings—satisfaction.
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5. Discussion Since significant differences were found between the two age groups used in this experiment, hypothesis 1 has not been supported by these experimental findings: provision of a combination of navigational aids does not eliminate the age differences. The slight deterioration identified by Dalgarno and Scott (2000) in navigation performance from the age of 40 may therefore perhaps be attributable to the age factor. It is noticeable, however, how performance times improved for older participants when they were presented with a variety of tools (in the ‘all controls’ interface condition). In this condition, the least difference in performance times between the two age groups was recorded with younger participants achieving an average time of 4 min, 56 s and older participants achieving an average time of 5 min, 30 s (see Table 2). Further work is necessary to investigate if this difference can be reduced or eliminated with further navigational support. The second hypothesis is supported by the results of the first simple contrast. There were statistically significant differences found between the performance times obtained for the ‘control’ group and each of the other interface conditions. The usability results also confirm this finding in that lower ratings were consistently awarded for the ‘control’ group and it was the only condition where a participant was unable to complete the set task. These findings support the authors’ earlier experimental conclusions (Sayers et al., 2000), emphasizing the need for the visual display of navigational aids on a two-dimensional interface. This conclusion can be applied to users of all ages. Hypothesis 3 predicts improved performance when a variety of navigation aids are provided rather than a single aid and is partly supported by the findings from this study. The interface displaying all the tools (‘all controls’) did produce statistically significant navigation times when compared with the interfaces displaying a map function and a speed function, respectively. There was no significant difference found, however, between this group and the ‘mark’ or ‘undo’ groups. This result indicates that these two tools (‘mark’ and ‘undo’) were found particularly useful for navigation and this is supported by observation of the participants, the ‘think-aloud’ technique employed, and the usability ratings scored. From observation and comments it was clear that the ‘mark’ tool was frequently used as a means of error correction—participants in both age groups used it to index useful viewpoints within the environment, to which they then teleported when encountering difficulty with the navigation task. The high usability ratings received for the ‘mark’ and ‘undo’ tools, when combined with the fact that there was no significant difference found between their performance times and that of the ‘all controls’ condition, point to the importance of effective error correction in the navigation process. The map tool was not found particularly useful in this experiment yet this finding needs to be treated with caution due to the small size of the VE presented. From observation of the participants, it was noticeable that the map was used infrequently and participants often stated that they found that they were not lost within the environment and did not need to use the tool. Earlier studies by Ruddle et al. (1999) show the usefulness of maps for navigation in very-large-scale VEs, so we can only conclude that a map might not be a particularly useful navigational aid in small VEs.
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6. Conclusions and future work This paper has presented the results of an experiment designed to investigate the effect of various interface tools and age on navigation performance times and user satisfaction. From the results presented, we can say that age has a significant effect on 3D navigation using desktop systems, with younger users consistently outperforming their older counterparts. As the user community for these types of applications broadens, age must be considered as an element in the design process, and the decrease in time differences between the two age groups when presented with a variety of tools suggests that further research into what factors might reduce (or eliminate) this gap are necessary. A study by Emery et al. (2003) suggests that multimodal interaction may be the way forward when designing for the next generation of older people who will be more familiar with computer technology as it continues to integrate every aspect of modern everyday life. Emery et al. (2003) found that the performance of older adults (aged 65 þ ) with varying levels of computing experience, was improved when using a Graphical User Interface with the use of some form of multimodal feedback (visual, auditory, haptic) as opposed to input, and that this was more noticeable the higher the level of computing experience. We can also conclude that the inclusion of visibly presented navigation aids has a significant beneficial effect on navigation performance times for all ages, resulting in better levels of user satisfaction. In addition, the abilities to mark user-defined locations within an environment, and to undo actions were found to produce the fastest performance times and to be the most highly rated individual tools. Further work involving large-scale VEs is needed to thoroughly test the effectiveness of individual tools such as the map and speed control facilities presented in this study.
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