ORIGINAL ARTICLE

Eleanor Marshall Æ Sarah Nichols

Interaction with a desktop virtual environment:a 2D view into a 3D world

Received: 12 December 2003 / Accepted: 26 March 2004 / Published online: 25 June 2004� Springer-Verlag London Limited 2004

AbstractWith the development of computer software andhardware in the past few years, it has been possible toproduce effective training virtual environments oneveryday personal computers with little expert trainingrequired for users or designers. However, the develop-ment of the equipment that enables this has brought littlecoinciding research on what features to include whendesigning these environments. Despite these increasedadvances in PC capabilities for desktop virtual environ-ments (VEs), there are still limitations on the number ofobjects that can be programmed to be interactive, usuallydue to restrictions on programming time and cost. As aresult, it is often left to the programmer to decide whichof the objects included to increase the realism of theenvironment will be interactive and which aesthetic. Thework presented in this paper is an experiment thataims to establish a guide for environment designers to aideffective environment interaction development byidentifying key elements in a VE design.

Keywords Desktop virtual environments Æ Interactionhotspots Æ Training Æ Virtual environmentdevelopment Æ Virtual environment design

1 Introduction

There is a need for research into the way users interactwith desktop virtual environments in order to providethe most natural and intuitive means of interaction forparticipants. Typical interaction in desktop virtualenvironments (VEs) is usually split into navigation andobject manipulation. In addition, in order to cope withthe relative simplicity of the input devices traditionally

used (mouse and joystick), participants are presentedwith both the physical interface of the input device andthe virtual interface, usually comprising a screen over-lay, toolbar or ‘‘move bar’’, or prompts, cues orinstructions embedded within the VE. This combinationof interfaces and types of interaction presents a chal-lenge in the development of VEs in terms of usability ofthe environment, presence experienced and the resultingeffectiveness of the VE.

Due to these restrictions on input devices, it is verydifficult to have natural or intuitive interaction meta-phors within the desktop environment. However, the useof a mouse as an interaction device takes advantage ofexisting user expectations from PC use by, for example,using a click to cause an object response. Similarly,games use has led to the mapping between joystickmovement and movement within a virtual world to beconsistent in terms of forwards and backwards move-ment and rotating left and right.

A number of users have adopted desktop VR (e.g.within education, training etc.) as a low-cost solutionthat provides 3D interaction without the need to committo the purchase of an expensive, dedicated piece ofhardware. This paper examines the way in which thevirtual interface should be designed to enhance interac-tion, usability and effectiveness, based on the assump-tion that only basic input devices will be used.

2 Interaction design for desktop virtual environments

The importance of realism, interaction and control ofmovement as an aspect of VE applications was exploredin Marshall et al. [1]. It has long been assumed thatinteraction is a ‘‘good thing’’; for example in a trainingVE, it could enhance the participant’s sense of beingthere (presence), the ease of use of the VE, and eventu-ally the effectiveness of navigational and spatial infor-mation training that may result from the period of VEuse. However, there is little empirical evidence avail-able to support this notion. This paper presents an

E. Marshall (&) Æ S. NicholsVirtual Reality Applications Research Team (VIRART),School of MMMEM, University of Nottingham,Nottingham, NG7 2RD, UKE-mail: Epxem1@nottingham.ac.uk

Virtual Reality (2004) 8: 17–25DOI 10.1007/s10055-004-0132-2

experiment that examines how to include interaction in adesktop VE and looks at whether the interaction adds tothe effectiveness of the VE.

2.1 Existing definitions of interaction

‘Interaction technique’ is the term used to describe themethods devised to communicate with and affect a VE,be it the interaction device itself or the theory behind itsoperation. Herndon et al. [2] define interaction tech-niques as the ‘interfaces one uses to complete a partic-ular task’.

Types of interaction within VEs can be classified intotwo groups – exocentric and egocentric. Exocentric canalso be called a ‘god’s eye’ viewpoint, where the partic-ipant selects items from outside the environment to usewithin it. An egocentric, or ‘worm’s eye’ viewpoint,allows interaction to be performed directly within theenvironment. Therefore, a prediction would be that wewould expect an environment that consisted of solelyegocentric interaction to lead to a higher level ofpresence, as participants are not required to go ‘outside’the environment in order to achieve interaction.

Bowman and Wingrave [3] divide interaction intofour ‘universal interaction tasks’ as follows:

– Navigation – moving the viewpoint through an envi-ronment, achieving both cognitive (way finding) andmotor (travel) goals.

– Selection – the task of choosing one or more objectsfrom a set.

– Manipulation – changing to the specification of anobject’s properties, i.e. position and orientation.

– System control – changing system state or mode ofinteraction.

Within this classification, we were particularly inter-ested in selection and manipulation. Navigation, par-ticularly with only 4 degrees of freedom (forward,backwards, left, right), is effectively achieved via a joy-stick, which is emerging as a standard navigation inputdevice. However, such standards for selection andmanipulation have not yet been established.

Marsh and Wright [4] take a slightly different ap-proach to interaction, and instead of defining it as astand-alone aspect of a VE, they consider interaction asa basis for the whole experience or ‘illusion’ of using avirtual world, and it is not considered as solely selectingan item and manipulating it to achieve a goal or create areaction. Presence is then considered to be a result ofparticipant interaction with the virtual space created bythe virtual world and is ‘broken’ by awareness of theartificiality of the medium. It is claimed, therefore, thatpresence is hindered by the practical problems of thetime and effort in producing the model and the com-plexity of that model.

Poupyrev et al. [5] state that interaction shouldmaximise user performance and result in efficientand enjoyable virtual interfaces. Herndon et al. [2]

considered methods of evaluating computer interfacesthat could provide a useful guidance tool of points toconsider in the design of interactive VEs, comprisinglayout/visibility, legibility/affordances, ergonomics,colour, shape and feedback. It is also noted that ‘youshould never have to read a label to understand howto use an object—its affordances should convey thisinformation’. In addition, Marsh and Wright [4] notedthat if the VE is ‘uninspiring, dull or boring to use, itwill not hold participant attention for any period oftime’. This puts forth a strong case for the inclusion ofinteraction within a VE to make it interesting, butfrom another angle the interaction method itselfmust also be made interesting to make the partici-pant wish to interact initially and maintain his/herattention.

2.2 Interaction requirements

From previous research and the authors’ own experiencethe following is assumed: If interaction is included in adesktop VE, it is important for the participant to:

– Know that it is possible to interact and that theinteraction

– Does not inhibit the usability of the VE or the pres-ence experienced by the participant and

– Contributes to the VE task effectiveness or goal of theperiod of VE use.

The following section considers previous literaturethat has examined different types of interaction and isused to identify how the goals above may be achieved.

2.3 Interaction hotspot theory

The term ‘Interaction hotspots’ was defined by the authorto refer to points within a VE that are interactive. Kauret al. [6] provided initial work into the development of amodel of interaction with VEs. The work was based onNorman’s theory of interaction with the real world [7].The aim was to provide a basis for developing designguidelines, including interaction, within VEs. The mainusability problems within virtual environments weredefined as

– Maintaining a suitable viewing angle– Navigating in tight areas– Losing whereabouts (once too close to objects)– Recognising interactive hotspots [6].

It is this final point that has been selected to study ingreater detail as interaction forms a fundamental aspectof training within VEs. It provides a way of supplyingmore information about areas of the environment and toteach tasks within the environment to apply to the realworld. Kaur et al. [6] note that ‘tasks in virtual envi-ronments are often loosely structured with moreemphasis on exploration and opportunistic action’. Thisdemonstrates that the opportunity to interact with the

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VE is almost infinite, so ways of encouraging the user tointeract with the important aspects of the environmentand where interaction can be used most effectively isessential. To emphasise this, Kaur et al. [6] also statethat ‘behaviour is primarily opportunistic following ofcues’.

On the basis of previous research, the concept ofinteraction hotspots was considered in more detail.Interaction hotspots are not centred on manipulationwith the goal of position and orientation as such, butrather on visual or audible feedback such as a change incolour or texture or even additional information pro-vided about a given object. The aim of an interactionhotspot is to suggest to a participant that interaction ispossible with that object. Inevitably, within a VE therewill be a large number of objects whose primary purposeis to add to photorealism and thus they do not respondto user input – for example, a picture on the wall in a VEmay look realistic, but it is unlikely to fall off the wall ifthe participant bumps into it, as would happen in thereal world.

In the experiment presented in this paper, we wereinterested in how different types of interaction promptsor cues affected the likelihood of interaction actuallytaking place, and whether the interaction impacted onthe effectiveness of the period of VE use. Therefore, itwas necessary to identify what types of interaction arepossible in a VE.

Most work within the area of interaction in virtualworlds is concerned with the method of communicatinguser intentions to the virtual world, be it via the inter-action device or the technique behind the use of thatdevice. To date there has been little research into aspectsthat entice a user to interact with the environment andthe consequences of that interaction; increased memoryretention for training environments, increased enjoy-ment, effectiveness and usability are all possible conse-quences of well-designed interaction hotspots. Manyareas of research into interaction techniques do provideuseful information on aspects of interaction hotspotdesign such as the importance of feedback, affordancesand so forth.

The concept of interaction hotspots falls within thecategories of selection and manipulation within VEinteraction and is mainly concerned with the selection ofobjects. This includes what prompts a user to select anobject and the effect that selection has on the user, forexample on memory retention. Interaction hotspots donot apply to the area of manipulation to such an extent,and although the object may be manipulated in someway within the environment, it is not the main purposeof that interaction. The consideration of interactionhotspots could prove important, even vital, for the de-sign of an effective and usable VE for a given purpose, inparticular a training environment where interactionhotspots can be used for a variety of purposes, such as toprovide specific information about an item or to aid inthe retention of that information or of the item’s loca-tion.

3 Experiment design and development

The aim of this experiment was to explore what promptsa user to interact with a VE. ‘Interaction hotspots’ havebeen defined by the author as specific points within a VEthat it is possible for the user to interact with. Thefundamental research question that motivated the studyand design of the interaction hotspots within theexperiment was ‘what will prompt a user to notice andinteract with a specific point in a VE?’

Eastgate [8] defines an interactive object as a ‘device’– any object that affords interaction, and it is the au-thor’s belief that hotspots that attract the attention ofthe user will entice that user to interact with the envi-ronment. According to Benjamin et al. [9], in the processof attention certain stimuli are selected over others inour perceptual world. In addition, there are certainstimuli that are universally attention drawing (notmainly dependent on the individual), for example nov-elty (i.e. an object out of context), colour, movement,size and repetition. Hilgard et al. [10] add intensity andcontrast to this list. Figure 1 provides an indication ofthe type of possible attention grabbing factors for usersof VEs that could be applied to interaction hotspots.

Also considered was how interaction hotspots withina VE may have an influencing effect on the usability ofthat environment. This may depend on many factorsconcerning the use and design of that environment. Forexample, if the task to be completed within the envi-ronment involves the manipulation of many objects,then it may be a highly influential factor. If the taskrequires navigation but little interaction, then the influ-ence of interaction design may be greatly reduced. Itmay also be the case that if an object is required toperform the set task (i.e. it is dark and the participantneeds to find a light switch to see what she is doing), theparticipant will actively seek out that object to interactwith it. If this is the case, then it is less likely that theappearance of the object within the environment will be

Fig. 1 Interacting with hotspots

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an influencing factor and more likely that its locationrelative to expectations from the real world will have animpact.

Table 1 consolidates the authors’ expectations withrespect to the design and positioning of interactionhotspots in a VE with reference to Fig. 1. This list is notexhaustive but highlights the key areas of interest forthis study.

In addition to this, also considered in the design ofinteraction hotspots and the testing of their effectivenesswas their usability within the environment. In work byKaur et al. [11], four points are made with respect to thedesign of objects within a VE to ensure usability; theobject is distinguishable and identifiable, the interactiv-ity and significance of objects are clear, and the object isaccessible. These factors in turn affect the design ofhotspots because they limit the possible use of abstract

colour/detail/movement/positioning. With this in mind,a set of cue types was developed (see Sect. 4.2 for de-tails). The cues were chosen as they combined attentiongrabbing features that would not distract from the dis-tinguishable and identifiable features of the environmentas recommended by Kaur et al. [11].

3.1 Experimental research questions

The main focus of the research questions was on theimpact of interaction hotspot design on user perfor-mance. The concepts of effectiveness, usability andpresence were also considered to provide more infor-mation regarding the impact of the VE design andresulting user performance on the participants’ overallexperience.

1. Do interaction hotspots prompt user interaction?2. Which interaction hotspots prompted the most user

interaction?3. Does interacting with the VE influence effectiveness

(transfer of knowledge, presence and usability) of thetraining environment?

4. Did the existence of a task during VE interactioninfluence interaction with and effectiveness of thetraining environment?

5. Are presence, usability and transfer of knowledgerelated to each other?

4 Method

4.1 Participants

Sixteen participants took part in the experiment (meanage 26 years 7 months, range 21–37), all of whom werestudents and employees of the University of Notting-ham. They had little or no previous experience withvirtual reality and were not familiar with the building onwhich the VE was based. All the participants werecomputer literate and were chosen because they repre-sented a selection of possible end users of a virtualreality application such as that tested.

4.2 VE design

The environment was modelled on a real manufacturinglaboratory at the University of Nottingham and con-sisted of 14 rooms. Instructions and a demonstrationwere provided for all the participants on how to navigatethe environment and how to open the door between eachroom.1

An egocentric design was chosen for the environment,with cues and interaction occurring within the participant

Table 1 Expectations from the design of interaction hotspots

Colour If the colour is unusual to thesurrounding environment, then itmay attract more attention andinteraction.

Movement Movement is likely to attract attentionand consequently interaction. If themovement is likely to occur in the realworld, it may attract less attention thanabstract movement.

Detail If an object appears as it would in thereal world (photo-realistic), it mayattract more attention than if it werein the same detail as the surroundingenvironment.

Expectedauditory cue

If an object makes a sound expectedby that object (i.e. a phone ringing),it may attract attention and interaction.

Abstractauditory cue

If the sound from an object isunexpected, it may encourage moreattention and therefore interaction,but in turn may reduce the realismof the object.

Real-worldfamiliarity

An object familiar to the user from thereal world may entice more interactionwith the object represented in thevirtual world.

Virtual-worldfamiliarity

If the participant has existing knowledgeof using a virtual environment, certainmethods of interaction may be familiar.This may aid the choice of interactionpoint by the participant.

Repetition The repetition of a task could resultin learning by the user as to whichobjects are interactive and maytherefore increase the attention drawnto such an object.

Prominentpositioning

If an object is placed in the user’s lineof vision, it may attract more attentionand imply interaction than ifit were not.

Expectedpositioning

An object placed in a position itwould be expected to be seen in isless likely to attract attention andencourage interaction.

Unexpectedpositioning

An object placed entirely out of contextis likely to attract more attentionand interaction.

1For this reason interaction with doors within the environment wasnot included in the results section.

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viewing screen as it was thought to have the least influenceon the presence and usability experienced by the user.

The images seen in Fig. 2 are taken directly from theenvironment that was developed.

Within the environment the selected interaction cueswere placed in eight categories with two sub-categories(flashing and highlighted). The different designs ofinteraction hotspots were selected on the basis of theliterature and were intended to allow some evaluation ofthe hotspot theory presented in Sects. 2.3 and 3. Thenon-interactive cues were featured to enhance the real-ism of the environment and to increase user interest. Asummary of the interaction hotspots and their frequencyis given in Table 2.

4.3 Materials and measures

Presence and usability were both measured using spe-cifically designed questionnaires [12]. Responses weremeasured using a five-point Likert scale. Each partici-pant was given a corresponding total presence orusability value according to his/her response. Demo-graphic information was provided using a questionnairecompleted before the experiment took place. Theexperiment was recorded on a split-screen video showingwhat was seen by the participant on the computermonitor and a video image of their actions using theinteraction devices. Data were collected by analysing

this video footage and noting how objects interactedwithin the environment.

4.4 Procedure

4.4.1 Part A – Free interaction condition

Eight participants were asked to navigate their wayround the VE using a joystick and were told to interactwith anything that interested them by using a mouse toclick on the object. There was no set task for them toperform whilst in the environment, and they were toldthey may stop when they had explored all possiblerooms within the environment.

4.4.2 Part B – Specific task condition

Eight participants were asked to navigate the sameenvironment and were told to interact with whateverthey chose whilst performing a search task within theenvironment for non-cued health and safety objects. Theparticipants were provided with an on-screen list so theyknew what they were searching for and when all objectshad been found.

The participants were then asked to attempt to recallthe location of the safety items searched for in thespecific task group in the real-world building on whichthe VE was based. This was used as a measure of theeffectiveness of the virtual training environment in theform of memory recall. For purposes not covered in thispaper, when the participants were asked to return to thereal-world environment, half were asked to return oneday later and half were asked to return one week later.As results between these two groups were not found tobe significantly different, the recall values are reportedas one group here.

5 Results

The following research questions related to interactiondesign were examined in the experimental analysis.

Fig. 2 Images from the environment demonstrating the chosencues used in position

Table 2 Interaction hotspot designs and their frequency within theVE

Cue type No. interactive No. non-interactive

Red flashing 7 0Red highlighted 7 0Blue flashing 7 0Blue highlighted 7 0Yellow flashing 7 0Yellow highlighted 7 0Grey flashing 7 0Grey highlighted 7 0Textured 4 32Photo-realistic 8 71Sound 3 3Movement 0 20

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1. Do interaction hotspots prompt user interaction?2. Which interaction hotspots prompted the most user

interaction?3. Does interacting with the VE influence effectiveness

(transfer of knowledge, presence and usability) of thetraining environment?

4. Did existence of a task during VE interaction influ-ence interaction with and effectiveness of the trainingenvironment?

5. Are presence, usability and recall performance relatedto each other?

5.1 Do interaction hotspots prompt user interaction?

As shown in Table 3, there was a significant differencebetween the number of interactions in the free interac-tion condition on cued and non-cued items(t=4.737,df=7, p<0.005). There was no significantdifference between the number of interactions in thespecific task condition on cued and non-cued items(t=0.671,df=7, p>0.05).

From the information gathered from all participants57.45% of interactions were on cued objects, 42.55% onnon-cued objects.

5.2 Which interaction hotspots promptedthe most user interaction?

It should be noted that the ‘flashing’ and ‘highlighted’categories combine use of different colours, but these aregrouped for purposes of analysis. Some participants alsoclicked on some cue types many times as, for examplethey appeared to enjoy the reaction within the environ-ment. Table 4 shows the mean number of interactionswith the different cue types.

Figure 3 shows the number of different types of cuedobject interacted with (for all participants) as a per-centage of the total available objects to interact with inthe environment.

It can be seen from the graph that the colours [bothstatic (highlighted) and flashing] and sound appeared tobe the most effective cues to interaction. However, theapparent low impact of texture, photorealistic andmovement cues may be due to their general proliferationaround the environment, and the relatively high numberof non-interactive cues of this type (Sect. 4.2).

5.3 Does interacting with the VE influence effectiveness(transfer of knowledge, presence and usability)of the training environment?

This research question was first examined by looking tosee if there was any association between the total num-ber of interactions with the environment and the per-formance on the recall task. No association between thenumber of attempted interactions and recall perfor-mance was found either for the entire participant groupor when examining the task and free interaction groupsseparately (total: r=0.289, df=14, p>0.05; specifictask: r=�0.409, df=6, p>0.05; free interaction:r=0.265, df=6, p>0.05). However, it should be notedthat, due to the large individual participant variability innumber of interactions, the pattern between these twovariables does not appear to be linear, and these corre-lation coefficients may be susceptible to influence fromoutliers.

The association between the number of successfulinteractions (i.e. those that elicited a visible or audibleresponse from the VE object) and recall performancewas also examined (Fig. 4). No associations were foundbetween successful interactions and recall performance(total: r=�0.317, df=14, p>0.05; specific task:r=�0.389, df=6, p>0.05; free interaction: r=0.294,df=6, p>0.05).

A significant overall association was found betweenthe number of interactions with the objects specificallyrelated to the recall task (i.e. the safety items) (r=0.662,

Table 3 Interactions with cued and non-cued objects

Interactionson cued objects

Interactionson non-cued objects

Specific task 280 206Free interaction 861 639

Table 4 Mean number of interactions with different cue types

Cue type No. of availablecues

Freeinteraction

Specifictask

Red 14 20.63 5.13Blue 14 20.75 5.5Grey 14 17.75 4.88Yellow 14 13 9.5Textured 36 5.75 0.88Movement 20 11 0.88Photo realistic 79 9.75 6.38Sound 3 7.5 1.25Highlighted 28 26.13 11.88Flashing 28 46 13.13 Fig. 3 Number of interactions with cue types as percentage of total

cue types in VE

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df=14, p<0.005). However, on closer examination, thissignificant correlation appeared to be due to the fact thatfor the participants who completed the specific task,both number of clicks on the task-related items andperformance on the recall task was higher, leading to anoverall trend and positive correlation (Fig. 5). This isreinforced by a lack of significant correlation for theindividual task groups (specific task: r=0.175, df=6,p>0.05; free interaction: r=0.434, df=6, p>0.05).

The relationship between number of interactionsand successful interactions with presence and usabilitywas also examined for the overall participant group.No significant correlations were found (total interac-tions and presence: r=0.290, df=14, p>0.05; totalinteractions and usability: r=0.208, df=14, p>0.05;successful interactions and presence: r=0.328, df=14,p>0.05; successful interactions and usability: r=0.200,df=14, p>0.05).

5.4 Did existence of a task during VE interactioninfluence interaction with and effectivenessof the training environment?

The total number of interactions, interactions with task-related items and successful interactions by participantsin the two task groups was compared. As would beexpected, a significant difference was found between thetwo groups for the number of task-related interactions(t=4.692, df=14, p<0.001). However, despite the largedifferences between the mean total interactions andsuccessful interactions for the two groups, as seen inTable 5, the difference between the groups on thesemeasures was not significant (total interactions: t=1.788,df=8.65, p>0.05; successful interactions: t=1.891,df=10.08, p>0.05). This was thought to be due to theinequality in variances between the two participantgroups.

In order to measure the VE effectiveness, the per-formance on the recall task, presence and usability rat-ings for the two groups were also compared (Table 6). Asignificant difference was found for recall performance,where participants who were given a specific task per-formed better than those who had been in the freeinteraction group (t=3.594, df=14, p<0.05), as shownin Fig. 5. However, there was no difference between thetwo groups for their ratings of presence or usability(presence: t=1.572, df=14, p>0.05; usability: t=0.164,df=14, p>0.05).

5.5 Are presence, usability and recall performancerelated to each other?

Finally correlations were used to examine the associa-tions between presence, usability and recall perfor-mance. A significant positive correlation was foundbetween presence and usability for all participants(r=0.745, df=14, p<0.001). However, no associationwas found between recall and either presence or usability

Fig. 4 Association between task-related interaction and recallperformance

Fig. 5 Comparison between items recalled and task-related inter-actions for free interaction and specific task conditions

Table 5 Summary ofinteractions Mean total

interactions (SD)Mean task-relateditems interactions (SD)

Mean successfulinteractions (SD)

Specific task group 60.75 (65.49) 17.38 (2.83) 29.00 (42.81)Free interaction group 187.50 (189.56) 6.38 (6.00) 95.00 (88.96)

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(recall and presence: r=0.321, df=14, p>0.05; recalland usability: r=0.04, df=14, p>0.05).

6 Discussion and Conclusions

6.1 Interaction

The results showed that, for the free interaction condi-tion in particular, participants were more likely tointeract with cued rather than non-cued objects. Themost effective interaction hotspots were the brightlycoloured highlighted objects (both flashing and static)and sound. This may be due to the fact that the othercue types such as photo realism and texture may haveseemed more likely to occur within either the VE or thereal world normally (i.e. are less ecologically valid andtherefore stand out more) and not solely to indicate thatthe object has a special purpose. For example, the brightcolours used for highlighting and flashing around ob-jects are less likely to be a part of the environmentnormally and as a result prompt more interest from theuser and entice her to interact with the object.

This suggests that, if the objective of the environmentbeing designed is to get the user to interact with theenvironment (i.e. to provide more information about theobject being interacted with), then bright coloured cuesare the best interaction hotspots to use.

It was also noted that a high percentage (Fig. 3) of allthe coloured cues in the entire environment were inter-acted with at some point by at least one participant.Though it is difficult to compare the use of differentinteraction cues directly in this experiment, as they allappeared differently and on different objects (so objecttype and location, for example, may come into consid-eration), this does provide another good indicator thatthey were the most effective interaction hotspots as theyprompted the most overall interaction.

Interaction also increased significantly when therewas no specific task for the user to perform in theenvironment. This may occur as the user becomes moresingularly focused on the task and is less likely to noticeor react to objects that are outside the requirements ofthat task. This also should be considered in environmentdevelopment if the aim is to encourage user interaction,generally or specifically.

It was also noted that task performance (in the caseof this experiment, object location recall in the real-world environment) was significantly associated with

interaction with task-related items (i.e. objects to be re-called). This may be as a result of the interaction with anobject causing memory consolidation (in this case theitem location) for the user. The inclusion of a task istherefore an important consideration if an environmentis being designed to teach the user about a specific aspectof that environment.

A significant positive relationship was evident be-tween presence and usability, demonstrating that theseaspects of the VE experience are related. As a result,both are important considerations in the design of anenvironment, and their influence on other factors ofdesign and effectiveness of a VE should be considered.

There was no clear relationship between the numberof interactions and usability and the number of inter-actions and presence; this indicates that interactionneither adds to nor detracts from the presence orusability experienced by the user. This is importantinformation to an environment designer if she wants toinclude interaction in a VE but is concerned with itsnegative effect on these aspects of user experience.

There was no significant relationship between pres-ence and the correct recall of items (i.e. task perfor-mance) and usability and the correct recall of items. Thissuggests that neither factor is essential in environmentdesign to make the environment effective, although theirinfluence on other factors in the user’s experience, suchas enjoyment and ability to perform the task, were notmeasured in this experiment. Therefore, the importanceof presence and usability should not be discounted onthe basis of this work alone.

6.2 Conclusions

Overall, the data obtained from this study suggest thatinteraction in a VE is important for task effectiveness toa certain extent, particularly when the interaction is di-rectly related to the task being completed by the VEparticipant. Therefore, the inclusion of interactive ele-ments in a desktop VE should be carefully considered,and if time/effort decisions are being made, detailedinteraction should be programmed for aspects of theinteraction that are directly related to the goal of the VE.

Of the different interaction cues included in the VE,colour appeared to be an effective cue that encouragedinteraction, both when flashing and statically high-lighted around an object. This is likely to be due to thefact that these cues are artificial and not predictablefrom the participant’s experience of the real world.Therefore, this result may not be transferable to abstractVEs that do not represent real-world images in someway (i.e. do not allow the participant to transfer theirprevious knowledge when attempting to use the VEintuitively). It is also important to note that, whilst thesecues appeared to encourage more interaction, the use-fulness of that interaction in terms of the goal of the VE(training memory for object location) was less clear andcertainly appeared low in comparison to the importance

Table 6 Summary of measures of effectiveness

Mean correctrecall (SD)

Mean usabilityscore (SD)

Mean presencescore (SD)

Specific taskgroup

9.25 (3.54) 105.88 (15.43) 36.00 (5.86)

Free interactiongroup

4.00 (2.14) 107.00 (11.82) 39.63 (2.88)

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of type of instruction (task-specific or free interaction)given to the participant.

One challenge that was encountered during thisstudy, and has been experienced in previous research inVR, is the vast individual differences in participantbehaviour (e.g. [13]). This possibly contributed to thelack of significant statistical findings in some parts of theexperiment, as in several cases very large standarddeviations were observed, and for example, the numberof interactions by participants ranged from 446 to 0!This is due to the very nature of VR and a direct resultof the fact that one of the benefits of a VE is that itallows freedom of movement and interaction. However,this lack of consistency between participants does pres-ent challenging methodological problems.

As has been found in previous research [1], and wouldbe expected from theoretical predictions, presence andusability were positively correlated. It was also expectedthat a high level of interaction would also have con-tributed to usability and presence, if indeed, as is com-monly assumed, interaction is a ‘good thing’. The resultsfrom this study do not support this assumption unlessinteraction is task directed, and importantly, interactionwas also not found to have a negative impact on VEeffectiveness.

One suspicion is that something that is enhanced byincreased levels of interaction is the participant’senjoyment of her experience in the VE. Therefore, par-ticipant enjoyment is being examined in a later study inthis programme of research.

This study has not been able to conclusively show thebenefit of interaction but has highlighted some differ-ences among interaction cue types and illustrated theimportance of task context for VE effectiveness. There-fore, it is vital that research continue to examine thisissue so that appropriate design decisions can be made inorder to ensure that effective VEs are developed in asefficient a manner as possible.

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