Transfer of Juggling Skills Acquired in a Virtual Environment

A. P. Hauge

, C. S. Kragegaard

, E. B. Kjæhr

and M. Kraus

School of Information and Communication Technology, Aalborg University, Aalborg , Denmark

Department of Architecture, Design and Media Technology, Aalborg University, Aalborg, Denmark

Keywords:

Natural Interaction, Virtual Training, Transfer of Skill, Juggling, Motor Skill, Simulation.

Abstract:

This paper explores whether motoric skills acquired within a virtual training environment can be successfully

transferred to the real world by comparing a virtual environment with a traditional learning environment.

Speciﬁcally, a system for learning juggling with virtual balls was designed with a focus on approximating

natural interaction. We propose a method of evaluating the acquisition and transfer of motoric skills through a

virtual environment, which is compared to a traditional learning environment. Each environment was evaluated

using various criteria ranging from improvement in skills to observations of performance. The ﬁndings suggest

that a transfer of motoric skills and knowledge takes place for users of the virtual system with only little

difference between the environments. They also suggest that a virtual environment can create a less frustrating

learning experience.

1 INTRODUCTION

Juggling is a sport that heavily involves motor skills

in order to facilitate throws from one hand to the other

without dropping a ball. It requires the user to learn

the basic techniques and to understand the rhythm.

Furthermore, the user has to anticipate coming events

to organize current actions (Beek and Lewbel, 1995).

The goal of the virtual learning environment pro-

posed in this work is to facilitate the acquisition of

transferable juggling skills in as effective a way as

possible. To this end, the physical motion of juggling

balls is simulated and appropriately modiﬁed in order

to allow for an improved learning experience.

The comparison of a virtual environment (VE) and

a traditional environment for learning motor skills

such as juggling can reveal whether training in a

VE could substitute training with physical balls – or

whether the loss of depth, spatial and tactile feedback

when using the VE also means a loss in the transfer

of motor skills. Apart from the transfer of knowledge,

we also investigate how a well-designed learning VE

compares to a more traditional learning environment;

in particular, we compare the efﬁcacy of the two en-

vironments.

The rest of the paper is structured as follows: Af-

ter a review of previous work, the design of the VE

is discussed. This is followed by a description of the

experiment and a presentation of the results. Finally,

the VE is discussed based on the obtained results.

2 PREVIOUS WORK

Prior research in the ﬁeld of acquisition of knowledge

in VEs has focused on virtual reality (VR) applica-

tions. This includes transfer of spatial knowledge (Pe-

ruch et al., 2000)(Witmer et al., 1996) and basic task-

related knowledge (Kenyon and Afenya, 1995). This

research suggests that virtual reality technology can

facilitate acquisition of transferable knowledge. (La-

garde et al., 2012) focused on teaching timing through

their VE. They found no signiﬁcant difference be-

tween learning juggling in a virtual and a real envi-

ronment. They also found that starting with balls at

slow speed and increasing the speed allowed subjects

to learn faster than with balls at normal speed.

However, VR equipment is not widely available

and as such is primarily used in professional training

simulators. The rise of computer-vision-based input

devices such as the Microsoft Kinect for consumer

use can bring the technology to a larger demographic

that could potentially beneﬁt from using a VE.

Using computer vision techniques, Charalambous

facilitated the learning of juggling with virtual balls

(Charalambous, 2005) and Marshall et al. studied the

enhancement of the presentation of juggling perfor-

mances with physical balls as well as advanced train-

ing by using juggling with physical balls as part of

games (Marshall et al., 2007). Our work is similar to

the work by Charalambous in that we also facilitate

the learning of juggling in a VE; however, we observe

the complete learning process. Moreover, we inte-

385

P. Hauge A., S. Kragegaard C., B. Kjæhr E. and Kraus M..

Transfer of Juggling Skills Acquired in a Virtual Environment.

DOI: 10.5220/0004215203850388

In Proceedings of the International Conference on Computer Graphics Theory and Applications and International Conference on Information

Visualization Theory and Applications (GRAPP-2013), pages 385-388

ISBN: 978-989-8565-46-4

 2013 SCITEPRESS (Science and Technology Publications, Lda.)

grate game elements in the VE to improve the learning

experience similar to the work by Marshall et al.

3 DESIGNING THE VIRTUAL

ENVIRONMENT

The VE was implemented using the Unity3D game

engine (Unity Technologies, 2011) and the Microsoft

Kinect controller and SDK (Microsoft Corporation,

2011) to track each hand of the player.

In the VE the player’s hands, are represented by

3D models such that the left hand appears on the left-

hand side of the screen and the right hand on the right-

hand side; see Figure 1.

Figure 1: A screenshot of a player juggling with 3 balls

using the virtual training environment.

A basic button-trigger-based system was created

to give users more control over releasing (i.e. throw-

ing) the balls. Alternative solutions were investigated

such as releasing the balls based on sudden decelera-

tion of the hands; however, players reported problems

with unintentional releases of balls. The motion of

balls in the VE is restricted to a plane parallel to the

view plane. Issues with using more degrees of free-

dom for the virtual balls have previously been identi-

ﬁed by Charalambous (Charalambous, 2005).

An important part in the design of the VE was

the dynamic difﬁculty adjustments during play. The

training starts with reduced gravity and therefore

slower motion of the balls. Furthermore, released

balls are initially assigned the appropriate velocity so

they reach the other hand. However, the player’s con-

trol over the balls’ velocity is gradually increased as

his or her score rises. The difﬁculty level is computed

by constantly checking the player’s score.

If the player scores higher than his or her previ-

ous score, the difﬁculty will increase and vice versa.

The difﬁculty is ﬁltered; thus, dropping a single ball

will not reset the difﬁculty but only reduce it slightly.

If the player continues to drop several balls, the difﬁ-

culty will decrease to help the player get back in the

game. This dependency on the player’s score results

in a basic dynamic difﬁculty adjustment intended to

challenge players without frustrating them, as sug-

gested by ﬂow theory (Csikszentmihalyi, 1997).

A level-based system in which new concepts are

gradually introduced (in this case, more balls), pro-

vides a less steep learning curve compared to that of

a traditional learning environment. To keep the at-

tention of the players, ﬂow theory (Csikszentmiha-

lyi, 1997) was used in the design of the levels. Each

level has a requirement containing a certain amount

of juggles before the next level is reached. Through-

out these levels, auditory cues are triggered when a

ball is dropped, thrown or a new ball is on the way.

The music also gradually changes based on the cur-

rent score and increases from a lower pitch up to

the normal speed of the music. Using a virtual sys-

tem might also assist in increasing the automation of

catching the balls, as the VE enables easy practicing.

By increasing the amount of practice, the automa-

tion should also become faster (Logan, 1988). Fail-

ures were designed to be entertaining as suggested

by Ravaja et al. (Ravaja et al., 2005). Thus, play-

ers are “rewarded” by visual and audio effects when

they drop balls in order to encourage them to continue

playing.

4 EXPERIMENT

The test subjects were mostly male and between 17

and 29 years. All were unable to juggle and had never

received prior training in juggling.

To compare the VE with the traditional learning

environment, test subjects were split into two groups.

Group 1 consisted of 14 subjects who used the VE.

Group 2 consisted of 15 subjects who used the tradi-

tional learning environment, i.e. physical balls. The

test setup shown in Figure 2 consisted of record-

ing equipment, the VE and a test facilitator to ob-

serve and take notes. Furthermore, an instructional

juggling training CD-ROM (Duncan Toys Company,

2011) was available for use. The traditional learning

environment was identical but without the screen and

the Kinect controller.

For the ﬁrst 5 minutes, the subjects of each group

were asked to throw as many or as few physical balls

from hand to hand as they were comfortable with. The

goal of this was to evaluate the basic level of motor

control and spatial awareness for each subject. After

this, a period of 35 minutes was spent training jug-

gling – 30 minutes for the users of the VE. During this

time, subjects were allowed to watch training videos

from a DVD. The DVD contained short videos with

descriptions for juggling one up to four balls. The

GRAPP2013-InternationalConferenceonComputerGraphicsTheoryandApplications

386

DVD

Figure 2: The test setup: laptop with instructional DVD (1),

test subject (2), Kinect controller (3), screen (4), facilitator

(5), spare balls (6), and recording equipment (7). In the

traditional environment (3) and (4) were removed.

subjects using the VE were then given 5 minutes to

adjust to throwing real balls. Finally, each group was

asked to juggle as many or as few physical balls they

could for 10 minutes in the same way they would do

if they were supposed to learn to juggle.

After the performance test, users were asked to ﬁll

out a questionnaire. Questions ranged from perfor-

mance self-assessment to rating their level of frustra-

tion during the test.

5 RESULTS

The performance score was created as an indication

of how well the player performed during the test. The

performance score was computed by ﬁrst counting

the number of throws from hand to hand per minute,

which was divided by the number of drops per minute.

This number x was then transformed by the function

(1− 1/(x+1))/3 resulting in a number between 0 (no

successful throws) to 1/3 (inﬁnitely many successful

throws). If the player was juggling with 2 balls in-

stead of 1 ball, 1/3 was added to the performance

score in order to reﬂect the higher performance. If

3 balls were used, 2/3 was added. The computation

is illustrated in Figure 3. If a test subject juggled with

different numbers of balls, only the score for the high-

est number of balls was considered in order to indicate

that the subject is at the next level. This also ensures

that a player, who only threw one ball, cannot have a

better performance than a player who has trained with

two balls.

Using a paired t-test it was possible to observe sig-

niﬁcantly better performances (probability level 0.05)

of both groups after the training. Comparing the im-

provements between the groups with an independent

t-test did not show a signiﬁcant difference: the tra-

ditional environment had only a 1.52% higher score

compared to the mean in the virtual environment. The

Figure 3: Model of how the performance is calculated.

Figure 4: Individual difference in user performance for each

learning environment (11 test subjects had to be culled from

the data due to using an incorrect juggling technique).

performance differences of all test subjects can be

seen in Figure 4.

When the virtual group answered the question-

naire, 57% of the subjects didn’t feel they would be

able to learn juggling by using the virtual environ-

ment. This shows that subjects were unaware of the

improvement they made. As the subjects were using

the virtual system they reported less frustration as op-

posed to the traditional learning environment, this was

also reﬂected in the questionnaire answers as shown

in Figure 5.

As depicted in Figure 6, subjects using the tradi-

tional learning environment felt it was difﬁcult — as

opposed to the subjects using the VE. 71% reported

that the VE was not too hard.

6 DISCUSSION

The lack of a signiﬁcant difference between the ac-

quired skills of the two groups suggests that the vir-

tual learning environment is comparable with the tra-

ditional learning environment as seen in Figure 4.

The results suggest that the acquisition of trans-

TransferofJugglingSkillsAcquiredinaVirtualEnvironment

387

Figure 5: Number of subjects reporting a level of frustration

from 1 (very frustrated) to 5 (very satisﬁed).1 test subject

didn’t ﬁll out the questionaire.

Figure 6: Number of subjects reporting a level of experi-

enced difﬁculty ranging from 1 (too difﬁcult) to 5 (too easy).

1 test subject didn’t ﬁll out the questionaire.

ferable motor skills is possible through training in a

VE. User feedback indicates that the dynamic difﬁ-

culty adjustments of gravity and velocity of thrown

balls created an experience where players were less

frustrated and provided a better training experience as

shown in Figures 5 and 6.

This could be explored further by letting the train-

ing span several days to reduce mental and physical

fatigue endured by subjects. Evaluating training over

longer periods of time would have been beneﬁcial as

the short time makes the data more prone to be due to

chance. The reason that it was not possible to ﬁnd any

difference between the two samples might also have

been due to the small sample size.

7 CONCLUSIONS

The experiment showed that the use of game design

can improve a training environment for juggling by

helping learners to maintain focus and by keeping the

learning experience engaging and interesting in spite

of a repetitive training process. This conﬁrms earlier

research by Marshall et al. (Marshall et al., 2007).

Since these results and observations have all been

gathered using juggling training, they can not be gen-

eralized to skills beyond juggling. In order to draw

broader conclusions on the use and beneﬁts of vir-

tual training environments for transfer of motor skills,

further research should be carried out across different

ﬁelds relying on motor skill development.

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