Arm Posture Changes and Influences on Hand Controller Interaction Evaluation in Virtual Reality
Round 1
Reviewer 1 Report
Undoubtedly, in a virtual reality environment, hand controller interaction is largely limited by the biomechanical structure of the upper limb and its kinematical features. Authors conducted an empirical experiment in which 30 participants were recruited to complete a series of target pointing and selection tasks in a specifically designed VR application. In this paper implications and suggestions also were discussed for designing more efficient and user-satisfied interactive spaces in VR.
My comments on this article are as follows:
- I propose to extend the background of the article with the fact that currently VR technology is more and more connected with other technologies, including the brain-computer interfaces technology. This will further enrich the article. For example, I propose to quote: Using BCI and VR Technology in Neurogaming, Analysis and classification of eeg signals for brain-computer interfaces, Book Series: Studies in Computational Intelligence, Volume: 852, pp. 93-99, DOI: 10.1007 / 978-3-030-30581-9_11 from 2020. The introduction to the article is relatively short.
- Please assign indexes to mathematical equations to the content of sentences.
- Please provide information on the basis of the group size and gender of the participants.
- I propose to extend Figure 3. The experimental setting and scenario with additional details related to the experiment. It is quite "dry".
- Please expand the Conclusions with plans for the future.
Author Response
Point 1: I propose to extend the background of the article with the fact that currently VR technology is more and more connected with other technologies, including the brain-computer interfaces technology. This will further enrich the article. For example, I propose to quote: Using BCI and VR Technology in Neurogaming, Analysis and classification of eeg signals for brain-computer interfaces, Book Series: Studies in Computational Intelligence, Volume: 852, pp. 93-99, DOI: 10.1007 / 978-3-030-30581-9_11 from 2020. The introduction to the article is relatively short.
Response 1: We agree on and appreciate the reviewer’s comment and suggestion on the background content. Admittedly, nowadays more and more cutting-edge technologies are increasingly integrated into VR, making it an increasingly prevalent tool in almost every domain. According to the reviewer’s suggetion, we have consulted and cited more relevant referrences, including the book section the reviewer mentioned, and extended the beginning of the article as follows:
“... VR has become an increasingly prevalent technology in sports and rehabilitation training [1], immersive entertainment [2] and education [3], and more other spatial simulation and exploration domains. For example, in geological research and educational practices, researchers have used the VR technology to recover and simulate geological heritages, which has been proven to be an effective means for immersive visiting and learning by academics and the public [4, 5]. Especially when other cutting-edge technologies such as natural language processing (NLP) and brain-computer interface (BCI) are integrated into VR, people have more opportunities to experience novel products and services, including but not limited to immersive storytelling, neurogaming and psychotherapy [6, 7] ... ”
We suppose that the extended background statement is more qualified for expressing the values and potentials of the VR technology, please refer to the revised manuscript to check our supplements (marked in red texts in the first paragraph and the newly supplemented references 4-7 at the end of the manuscript).
Point 2: Please assign indexes to mathematical equations to the content of sentences.
Response 2: We appreciate the reviewer to point out the lack of the equation indexes in the content.
In the revised manuscript, we have supplemented indexes, i.e., equations 1, 2, and 3, in the content sentences, please refer to the newly submitted manuscript to check all our revisions.
Point 3: Please provide information on the basis of the group size and gender of the participants.
Response 3: We appreciate the reviewer’s comment on the experimental design in group size and gender. In fact, we determined and organized the participants group for specific reasons: first, in regard to the group size, we had ever conducted a survey on the most representative empirical studies in HCI domain in recent 5 years and found that the amount of the participants engaged in most empirical studies ranged from 6 to 30. Based on this, we suppose that a group size of 30 is appropriate and sufficient in this experiment. In addition, in regard to the gender ratio, we had ever surveyed 300 volunteers through a questionnaire, and found that 69 of them were qualified participants. Most of these participants ( > 90.0%) were young users aged from 21 to 36, indicating that users younger than 21 or elder than 36 were uncommon users of VR technologies. Among these 69 participants, there were 18 females (26.2%) while others were males, indicating that male users had a far larger percentage than female users of VR applications. Based on these, 22 males and 8 females were selected as participants. We agree that an interpretation on the group size and gender ratio of the participants is necessary and benefical to this manucript. We have supplemented above interpretation at the end of the discussion, which is marked in red texts in the 19th page.
Point 4: I propose to extend Figure 3. The experimental setting and scenario with additional details related to the experiment. It is quite "dry".
Response 4: We appreciate the reviewer’s comment on the Figure 3. According to the reviewer’s suggestion, we have updated and extended the caption of the Figure 3 as follows:
“Figure 3. An illustration about the experimental setting and scenario: A male participant was acquiring a target through a handheld controller of Oculus Touch. A flat screen configured beside the participant was used to present and monitor the task procedure.”
Please refer to the 7th page to check the above update in the revised manuscript.
Point 5: Please expand the Conclusions with plans for the future.
Response 4: We appreciate the reviewer’s suggestion on the future work in the Conclusions. We have supplemented a brief statement about our future plan at the end of the Conclusions as follows:
“... More complicated interaction cases, including the young and the elder engaged tasks and two hands cooperative performance, were not considered in the current study, but they have been planed in the future work.”
Author Response File: 
Author Response.docx
Reviewer 2 Report
The present manuscript describes research finding from an applied project that aims to explore the impact of different arm postures on task performances in immersive virtual environments. It also reports results from an experimental investigation based on the acquired data of 30 participants. The manuscript is well structured and written, and the results could be beneficial fort he international research debate. There are however a couple of points the authors could improve when preparing a revised version of the manuscript:
- I understand that this experiment is focused on a rather technical aspect (impact of arm postures on task performance). Nevertheless, I would not reduce the application fields of immersive VR to training, entertainment and education (l. 30). VR (when applied) is inherently bound to motion in a spatial setting. This is the reason why geo disciplines, such as geography, cartography, geodesy, cultural heritage, urban planning etc. have dealt a lot with exploring modern VR possibilities. It would show the broader context and relevance of VR research at the beginning of your if you referred to some examples. Such recents studies coould be, for instance, https://doi.org/10.3390/ijgi10030150, https://doi.org/10.1007/s42489-021-00092-1 and/or https://doi.org/10.3390/geosciences12010009
- Your discussion section is detailed, no doubt. However, in its current version, it remains unconnected tot he ongoing state-of-the-art debate. The same applied to the conclusions section. While you cite 30 studies in the introduction and background section, you do not refer to a single reference in the discussion section. Could you please link your outcomes with previous studies? In how far do your experimental results back up, extend or even contradict previous results?
- In ll. 526-535, you summarize post-study comments. Some of them point to participants‘ uncertainties when conducting the experiment. How did you statistically guarantee that your participants‘ results did not cause outlier performances?
Author Response
Point 1: I understand that this experiment is focused on a rather technical aspect (impact of arm postures on task performance). Nevertheless, I would not reduce the application fields of immersive VR to training, entertainment and education (l. 30). VR (when applied) is inherently bound to motion in a spatial setting. This is the reason why geo disciplines, such as geography, cartography, geodesy, cultural heritage, urban planning etc. have dealt a lot with exploring modern VR possibilities. It would show the broader context and relevance of VR research at the beginning of your if you referred to some examples. Such recents studies coould be, for instance, https://doi.org/10.3390/ijgi10030150, https://doi.org/10.1007/s42489-021-00092-1 and/or https://doi.org/10.3390/geosciences12010009.
Response 1: We appreciate the reviewer’s comment and suggestion on the introduction about the VR technology and related examples. We agree that VR technology is inherently suitable for and apt to simulating three-dimensional spaces and based on this providing immersive user experience. From this perspective, geography and geology relevant applications and activities are especially suitable to be simulated and experienced in VR environment. According to the reviewer’s suggestion, to provide a more accurate and clearer introduction about the respresentative applications and potentials of the VR technology, we have retrieved and cited more literature, including the ones suggested by the reviewer, and revised the beginning of the introduction as follows:
“... VR has become an increasingly prevalent technology in sports and rehabilitation training [1], immersive entertainment [2] and education [3], and more other spatial simulation and exploration domains. For example, in geological research and educational practices, researchers have used the VR technology to recover and simulate geological heritages, which has been proven to be an effective means for immersive visiting and learning by academics and the public [4, 5]. Especially when other cutting-edge technologies such as natural language processing (NLP) and brain-computer interface (BCI) are integrated into VR, people have more opportunities to experience novel products and services, including but not limited to immersive storytelling, neurogaming and psychotherapy [6, 7] ... ”
In the above revisions, we supplemented a statement about the VR’s advantage in 3D virtual space simulation, and briefly presented an example to state the VR application in geological research and educational practices.
Point 2: Your discussion section is detailed, no doubt. However, in its current version, it remains unconnected to the ongoing state-of-the-art debate. The same applied to the conclusions section. While you cite 30 studies in the introduction and backgsround section, you do not refer to a single reference in the discussion section. Could you please link your outcomes with previous studies? In how far do your experimental results back up, extend or even contradict previous results?
Response 2: We accept and appreciate the reviewer’s comment and suggestion on the discussion content. The rsearch objectives and hypotheses were developed on the basis of the earlier studies review, and thus it is necessary and significant to connect and compare the current study with other studies in the discussion. According to our summary, there are mainly three aspects this study supplemented and extended previous studies: (1) Compared to the earlier research by Hincapié-Ramos et al. [14] and Lou et al. [21], the current study gained a more comprehensive understanding about the arm posture change and its dependent changes in perceived arm fatigue and user experience, which is beneficial for developing a more scientific metric for quantitatively measuring user comfort and overall user experience quality. (2) Neurophysiological studies revealed that human visual perception had a close correlation and a dominant effect on visually-guided hand operations, which had been widely referred to explain the hand interaction difference in upper and lower visual fields in earlier studies [38, 39]. But in this study, we suppose that it was the more obviously perceived arm fatigue in an upraised arm posture generated a lower hand interaction accuracy than that through a downward arm posture. From this perspective, this study provided a new evidence for explaining and predicting hand interaction difference at distinct heights. (3) From an ergonomical evaluation perspective, this study also provided a new view on the evaluation method of hand controller interaction. Although Fitts’ law [36] is a most classical and universally accepted theoretical model in earlier HCI evaluation practices [21, 22, 28, 35], it concerns little on the handedness characteristic, hand choice and their influences on the interaction performance that have been revealed in this study. Therefore, the newly achieved findings will also enlighten the following researchers to propose an updated Fitts’ law model to make it more applicable to hand controller interaction evaluation in a 3D space.
We have supplemented above content at the beginning of the discussion section (marked in red texts in the pages 17-18).
Point 3: In ll. 526-535, you summarize post-study comments. Some of them point to participants’ uncertainties when conducting the experiment. How did you statistically guarantee that your participants’ results did not cause outlier performances?
Response 3: We appreciate the reviewer’s comment on the post-study comments. In fact, we had applied two means to guarantee that the participants’ comments and task performance objectively reflect the experimental findings. Firstly, given the post-study comments from a few participants, we connected their comments to their task performance so as to verify whether their comments were in line with their performance in the interaction tasks. At the same time, we also asked all other participants whether they approve or disagree on the comments. Finally, we found that the subjective comments were mostly consistent with objective performance result. Secondly, as we stated in the section of 4.5 (in the 9th page), performance data that were more than 3 standard deviations from the mean values (Z-score > 3.0) were treated as outliers and excluded, thus to ensure that obvious outliners were not included in the formal analyses.
To eliminate the potential doubt the reviewer pointed out, and more importantly to improve the reliability of the results reported, we have extended the earlier summary about the post-study comments. Please refer to the 17th page to check the update (lines 537-549).
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
Dear Authors,
Thank you for the changes made.
I recommend the manuscript for publication in its current form.
Reviewer 2 Report
The authors submitted a revised version of the manuscript. The changes are thoroughly explained in a response letter, and the argumentation appears sound to me. Against this background, I would like to recommend this manuscript for publication.
