Original: It’s Over There: Designing an Intelligent Virtual Agent That Can Point Accurately into the Real World
Revised: It’s Over There: Designing an Intelligent Virtual Agent That Can Point Accurately into the Real World

Original: A BSTRACT
Revised: A BSTRACT

Original: It is challenging to design an intelligent virtual agent (IVA) that can point from the virtual to the real world and have users accurately recognize where it is pointing due to differences in perceptual cues between the two spaces.
Revised: It is challenging to design an intelligent virtual agent (IVA) that can point from the virtual to the real world and have users accurately recognize where it is pointing due to differences in perceptual cues between the two spaces.

Original: We designed an IVA with factors including: a situated display, appearance, and pointing gesture strategy to establish whether it is possible to have an IVA point accurately into the real world.
Revised: We designed an IVA with factors including: a situated display, appearance, and pointing gesture strategy to establish whether it is possible to have an IVA point accurately into the real world.

Original: With a real person pointing as a baseline, we performed an empirical study using our designed IVA and demonstrated that participants perceived the IVA’s pointing to a physical location with comparable accuracy to a real person baseline.
Revised: With a real person pointing as a baseline, we performed an empirical study using our designed IVA and demonstrated that participants perceived the IVA’s pointing to a physical location with comparable accuracy to a real person baseline.

Original: Specifically, we found that when the IVA is 230 cm away from the targets on average, the IVA outperformed the real person in the vertical dimension (10.22 cm, 28 .
Revised: Specifically, we found that when the IVA is 230 cm away from the targets on average, the IVA outperformed the real person in the vertical dimension (10.22 cm, 28 .

Original: 8% less error)
Revised: 8% less error)

Original: and achieved the same level of accuracy (11.58 cm) horizontally.
Revised: and achieved the same level of accuracy (11.58 cm) horizontally.

Original: Our integrated design choices provide a foundation for design factors to consider when designing IVAs for pointing and pave the way for future studies and systems in providing accurate pointing perception.
Revised: Our integrated design choices provide a foundation for design factors to consider when designing IVAs for pointing and pave the way for future studies and systems in providing accurate pointing perception.

Original: interaction (HCI) techniques—Pointing centered  design—Empirical studies in inter
Revised: interaction (HCI) techniques—Pointing centered computing—Interaction design—Empirical studies in inter

Original: 1 I NTRODUCTION
Revised: 1 I NTRODUCTION

Original: Many researchers have studied natural human communication cues such as voice and hand gestures [8,21,42].
Revised: Many researchers have studied natural human communication cues such as voice and hand gestures [8,21,42].

Original: One important aspect of human communication is deictic pointing [18,52], a hand gesture that complements or replaces verbal communication indicating a point of interest in a shared environment [36].
Revised: One important aspect of human communication is deictic pointing [18,52], a hand gesture that complements or replaces verbal communication indicating a point of interest in a shared environment [36].

Original: The pioneering work, Put that there [9] demonstrated how an intelligent virtual agent (IVA) can recognize and interpret a person’s pointing gestures at2D objects in a 2D virtual world to facilitate natural humancomputer interaction.
Revised: The pioneering work, Put that there [9] demonstrated how an intelligent virtual agent (IVA) can recognize and interpret a person’s pointing gestures at objects in a 2D virtual world to facilitate natural human-computer interaction.

Original: This work motivates the reverse question, “Can an IVA point back to the real world?”
Revised: This work motivates the reverse question, “Can an IVA point back to the real world?”

Original: More recently, with the advances in voice-based IVAs, such as Amazon Alexa, the emerging 3D display technologies provide opportunities for IVAs to perform deictic pointing to objects in the real world.
Revised: More recently, with the advances in voice-based IVAs, such as Amazon Alexa, the emerging 3D display technologies provide opportunities for IVAs to perform deictic pointing to objects in the real world.

Original: We believe that enabling IVAs with pointing gestures can enrich the communication channel and promote efficient human-like interactions [32].
Revised: We believe that enabling IVAs with pointing gestures can enrich the communication channel and promote efficient human-like interactions [32].

Original: To enable IVAs to point effectively, we seek to answer how ac- curately users can interpret the direction of an IVA’s pointing, to establish a fundamental building block for designing deictic interac- tions between users and IVAs.
Revised: To enable IVAs to point effectively, we seek to answer how ac- curately users can interpret the direction of an IVA’s pointing, to establish a fundamental building block for designing deictic interac- tions between users and IVAs.

Original: However, it remains unclear whether it is feasible to design an IVA that have users accurately recognize where the IVA is pointing into the real world.
Revised: However, it remains unclear whether it is feasible to design an IVA that have users accurately recognize where the IVA is pointing into the real world.

Original: Optimally, users should be able to interpret an IVA’s pointing to the real world as well as, or even better than a real person’s pointing.
Revised: Optimally, users should be able to interpret an IVA’s pointing to the real world as well as, or even better than a real person’s pointing.

Original: To explore this potential, we introduce design factors that may improve the chances that users would be able to perceive the IVA’s pointing accurately to demonstrate feasibility.
Revised: To explore this potential, we introduce design factors that may improve the chances that users would be able to perceive the IVA’s pointing accurately to demonstrate feasibility.

Original: These include the situated display , IVA appearance and pointing gesture strategies.
Revised: These include the situated display , IVA appearance and pointing gesture strategies.

Original: For the situated display , we used a spherical Fish Tank Virtual Reality (FTVR) display in our IVA design.
Revised: For the situated display , we used a spherical Fish Tank Virtual Reality (FTVR) display in our IVA design.

Original: Unlike immersive displays, the spherical FTVR display is calibrated to be viewer-aware in the real-world coordinate system, enabling the IVA to point from the virtual world to objects in the real world.
Revised: Unlike immersive displays, the spherical FTVR display is calibrated to be viewer-aware in the real-world coordinate system, enabling the IVA to point from the virtual world to objects in the real world.

Original: It also offers effective 3D depth cues for pointing perception (i.e., stereoscopic cue and motion parallax)
Revised: It also offers effective 3D depth cues for pointing perception (i.e., stereoscopic cue and motion parallax)

Original: Besides, spherical displays have been found to provide better gaze [26,48], size and depth [61] perception compared to the flat displays.
Revised: Besides, spherical displays have been found to provide better gaze [26,48], size and depth [61] perception compared to the flat displays.

Original: For the IVA appearance , we used an animated cartoon character that was not photo-realistic but offered natural, easy-to-control pointing affordances to avoid the Uncanny Valley [45] effect.
Revised: For the IVA appearance , we used an animated cartoon character that was not photo-realistic but offered natural, easy-to-control pointing affordances to avoid the Uncanny Valley [45] effect.

Original: For the pointing gesture , we designed our IVA to point following the arm vector instead of the eye-fingertip alignment commonly found in human pointing [7,28–30, 35] as it has been shown to provide a more accurate cue.
Revised: For the pointing gesture , we designed our IVA to point following the arm vector instead of the eye-fingertip alignment commonly found in human pointing [7,28–30, 35] as it has been shown to provide a more accurate cue.

Original: With a real person pointing as the baseline for comparison, we conducted an empirical experiment to investigate how accurately users can perceive our IVA’s pointing.
Revised: With a real person pointing as the baseline for comparison, we conducted an empirical experiment to investigate how accurately users can perceive our IVA’s pointing.

Original: As an IVA is usually smaller than a real person due to the size constraint of typical displays, we controlled for retinal size in the experimental design.
Revised: As an IVA is usually smaller than a real person due to the size constraint of typical displays, we controlled for retinal size in the experimental design.

Original: Our results demonstrated that it is feasible to have an IVA accurately point to locations in the real world.
Revised: Our results demonstrated that it is feasible to have an IVA accurately point to locations in the real world.

Original: Further, the IVA’s pointing location was perceived as accurately as a real person in our configuration.
Revised: Further, the IVA’s pointing location was perceived as accurately as a real person in our configuration.

Original: Specifically, the IVA outperformed the real person in the vertical dimension and yielded the same level of accuracy horizontally.
Revised: Specifically, the IVA outperformed the real person in the vertical dimension and yielded the same level of accuracy horizontally.

Original: We also discuss how the set of design factors may have contributed to the result and suggest design implications.
Revised: We also discuss how the set of design factors may have contributed to the result and suggest design implications.

Original: Thus, the design factors we suggest provide a foundation for future studies on exploring the relative importance of each factor to consider for the design of IVA with pointing gestures.
Revised: Thus, the design factors we suggest provide a foundation for future studies on exploring the relative importance of each factor to consider for the design of IVA with pointing gestures.

Original: We believe our study and IVA design help pave the way for research on users’ perception of pointing either in the virtual environment or in the real world.
Revised: We believe our study and IVA design help pave the way for research on users’ perception of pointing either in the virtual environment or in the real world.

Original: 2 R ELATED W ORK 2.1 Pointing in Intelligent Virtual Agents (IVAs)
Revised: 2 R ELATED W ORK 2.1 Pointing in Intelligent Virtual Agents (IVAs)

Original: Pointing is a fundamental building block of human communication [34].
Revised: Pointing is a fundamental building block of human communication [34].

Original: The ubiquity of pointing drives research on incorporating it for intelligent virtual agents (IVAs) in virtual environments [51].
Revised: The ubiquity of pointing drives research on incorporating it for intelligent virtual agents (IVAs) in virtual environments [51].

Original: Most prior studies on IVAs with pointing focus on its benefits in drawing users’ attention to some content in the virtual world where the IVA is situated.
Revised: Most prior studies on IVAs with pointing focus on its benefits in drawing users’ attention to some content in the virtual world where the IVA is situated.

Original: For example, the Persona agent [2] could point to images on web pages and Jack, as a virtual meteorologist, can give a weather report by pointing to the weather images [47].
Revised: For example, the Persona agent [2] could point to images on web pages and Jack, as a virtual meteorologist, can give a weather report by pointing to the weather images [47].

Original: Atkinson [4] showed an animated virtual agent serving as a tutor in a knowledge-based learning environment and demonstrated the ben- efits of pointing in directing the learners’ attention.
Revised: Atkinson [4] showed an animated virtual agent serving as a tutor in a knowledge-based learning environment and demonstrated the ben- efits of pointing in directing the learners’ attention.

Original: When combined with speech and context, using the Behavior Expression Animation Toolkit (BEAT), an agent was created to generate correlated gestures by extracting the linguistic and contextual information from the input text [13].
Revised: When combined with speech and context, using the Behavior Expression Animation Toolkit (BEAT), an agent was created to generate correlated gestures by extracting the linguistic and contextual information from the input text [13].

Original: To achieve deictic believability, Lester et al.
Revised: To achieve deictic believability, Lester et al.

Original: [37] designed
Revised: [37] designed

Original: COSMO agent, using a deictic planner to determine the generation of pointing guided by the spatial deixis framework.
Revised: COSMO agent, using a deictic planner to determine the generation of pointing guided by the spatial deixis framework.

Original: Rather than pointing to the virtual environment, an agent called MACK , in mixed reality, could point to a physical paper map shared with users in reality along with speech [12].
Revised: Rather than pointing to the virtual environment, an agent called MACK , in mixed reality, could point to a physical paper map shared with users in reality along with speech [12].

Original: However, an unanswered question is how accurately can an IVA point to the real world.
Revised: However, an unanswered question is how accurately can an IVA point to the real world.

Original: 2.2 Perception of Pointing in the Real World
Revised: 2.2 Perception of Pointing in the Real World

Original: When humans perform pointing naturally, without instructions, instead of pointing using their arm vector, Bangerter & Oppenheimer [7] and Henriques & Crawford [28] observed that humans commonly orient their arm so that the fingertip intersects the line joining the target and their dominant eye while gazing at the target.
Revised: When humans perform pointing naturally, without instructions, instead of pointing using their arm vector, Bangerter & Oppenheimer [7] and Henriques & Crawford [28] observed that humans commonly orient their arm so that the fingertip intersects the line joining the target and their dominant eye while gazing at the target.

Original: This is called eye-fingertip alignment as illustrated in Figure 2 c2.
Revised: This is called eye-fingertip alignment as illustrated in Figure 2 c2.

Original: This mechanism was further shown in the estimation of human pointing direction.
Revised: This mechanism was further shown in the estimation of human pointing direction.

Original: With various methods proposed, the head-hand line [16,39,44] (also known as the eye-fingertip line) was found to be the most reliable (90%) compared to forearm direction and head orientation [46].
Revised: With various methods proposed, the head-hand line [16,39,44] (also known as the eye-fingertip line) was found to be the most reliable (90%) compared to forearm direction and head orientation [46].

Original: Mayer et al.
Revised: Mayer et al.

Original: [41] demonstrated that it yielded the lowest offset among four other ray cast techniques.
Revised: [41] demonstrated that it yielded the lowest offset among four other ray cast techniques.

Original: As our study is to find factors that enable an IVA to point into the real world accurately, the impact of different alignment strategies is considered in our IVA design.
Revised: As our study is to find factors that enable an IVA to point into the real world accurately, the impact of different alignment strategies is considered in our IVA design.

Original: Pointing behavior during interpersonal interaction typically in- volves the movement of eye gaze, head and arm [28].
Revised: Pointing behavior during interpersonal interaction typically in- volves the movement of eye gaze, head and arm [28].

Original: Considerable research has been done targeting gaze perception.
Revised: Considerable research has been done targeting gaze perception.

Original: People can ac- curately discern their mutual gaze with another person [3,24] and the direction of the other person’s gaze [23].
Revised: People can ac- curately discern their mutual gaze with another person [3,24] and the direction of the other person’s gaze [23].

Original: By contrast, research on the perception of pointing accuracy is scant.
Revised: By contrast, research on the perception of pointing accuracy is scant.

Original: By evaluating the detection accuracy for different combinations of head, eye and hand pointing cues, Butterworth and Itakura [10] showed that pointing can improve spatial localization of targets when compared to head and gaze cues but suggested that pointing had limited accuracy.
Revised: By evaluating the detection accuracy for different combinations of head, eye and hand pointing cues, Butterworth and Itakura [10] showed that pointing can improve spatial localization of targets when compared to head and gaze cues but suggested that pointing had limited accuracy.

Original: Bangerter & Oppenheimer [7] contested their findings with a more precise measurement technique.
Revised: Bangerter & Oppenheimer [7] contested their findings with a more precise measurement technique.

Original: The results revealed that the detection accuracy was comparable to the accuracy level for eye gaze and it was unaffected by the exclusion of eye gaze and head orientation.
Revised: The results revealed that the detection accuracy was comparable to the accuracy level for eye gaze and it was unaffected by the exclusion of eye gaze and head orientation.

Original: Despite the good accuracy, they observed a perceptual bias towards the side of the pointer’s arm away from the observer in the horizontal dimension and above the target in the vertical direction.
Revised: Despite the good accuracy, they observed a perceptual bias towards the side of the pointer’s arm away from the observer in the horizontal dimension and above the target in the vertical direction.

Original: It was illustrated that the ambiguity introduced by the deviation between the eye-fingertip line and arm line might account for it.
Revised: It was illustrated that the ambiguity introduced by the deviation between the eye-fingertip line and arm line might account for it.

Original: A study by Cooney et al.
Revised: A study by Cooney et al.

Original: [19] evaluated the pointing accuracy in the horizontal direction and replicated Bangerter & Oppenheimer’s results.
Revised: [19] evaluated the pointing accuracy in the horizontal direction and replicated Bangerter & Oppenheimer’s results.

Original: Con- sidering the ambiguity shown in human pointing and exploiting the fact that we have explicit control over the IVA’s head, eye and finger positioning, we designed our IVA to use arm vector pointing rather than eye-fingertip alignment as an approach to improve its pointing accuracy as illustrated in Figure 2.
Revised: Con- sidering the ambiguity shown in human pointing and exploiting the fact that we have explicit control over the IVA’s head, eye and finger positioning, we designed our IVA to use arm vector pointing rather than eye-fingertip alignment as an approach to improve its pointing accuracy as illustrated in Figure 2.

Original: Finally, during interpersonal interactions, the accuracy with which observers can detect the pointed targets based on another person’s pointing gestures has been a key issue.
Revised: Finally, during interpersonal interactions, the accuracy with which observers can detect the pointed targets based on another person’s pointing gestures has been a key issue.

Original: Because if a person cannot accurately interpret the other’s pointing direction, it would be difficult to establish joint attention within a conversation [10].
Revised: Because if a person cannot accurately interpret the other’s pointing direction, it would be difficult to establish joint attention within a conversation [10].

Original: Prior research shows that the distance between users and targets can affect users’ interpretation of the pointing direction [5,16,59].
Revised: Prior research shows that the distance between users and targets can affect users’ interpretation of the pointing direction [5,16,59].

Original: To study this effect, we configured the distance as an independent variable to investigate how the accuracy changes in different distances.
Revised: To study this effect, we configured the distance as an independent variable to investigate how the accuracy changes in different distances.

Original: 2.3 Perception of Pointing in Virtual Environments
Revised: 2.3 Perception of Pointing in Virtual Environments

Original: While pointing is ubiquitous in daily interactions within the real world, it is difficult for users to precisely interpret the pointing direction in virtual environments.
Revised: While pointing is ubiquitous in daily interactions within the real world, it is difficult for users to precisely interpret the pointing direction in virtual environments.

Original: Wong and Gutwin [59] compared users’ accuracy in a collaborative virtual environment (CVE) with the real world and observed worse performance in CVE although the difference was smaller than expected.
Revised: Wong and Gutwin [59] compared users’ accuracy in a collaborative virtual environment (CVE) with the real world and observed worse performance in CVE although the difference was smaller than expected.

Original: The immersive head-mounted displays (HMDs) and virtual reality (VR) systems (e.g., CAVE) only support pointing within the virtual environment where the IVA is situated.
Revised: The immersive head-mounted displays (HMDs) and virtual reality (VR) systems (e.g., CAVE) only support pointing within the virtual environment where the IVA is situated.

Original: By merging the real world with the virtual environment, FTVR [58] displays enable the IVA to point from the virtual world to the real world and provide a mixed reality experience.
Revised: By merging the real world with the virtual environment, FTVR [58] displays enable the IVA to point from the virtual world to the real world and provide a mixed reality experience.

Original: Our ex- periment used a spherical FTVR display because it has advantages over other VR/AR displays and planar displays as we will discuss in Section 3.1.
Revised: Our ex- periment used a spherical FTVR display because it has advantages over other VR/AR displays and planar displays as we will discuss in Section 3.1.

Original: Regarding the evaluation of users’ perception of pointing in FTVR, previous research focused on the assessment of pointing cues.
Revised: Regarding the evaluation of users’ perception of pointing in FTVR, previous research focused on the assessment of pointing cues.

Original: Kim et al.
Revised: Kim et al.

Original: [33] classified the pointing cue factors to consist of three levels: gaze, hand, and gaze+hand.
Revised: [33] classified the pointing cue factors to consist of three levels: gaze, hand, and gaze+hand.

Original: They found no significant difference among the three levels with an experiment in a cylindri- cal 3D display.
Revised: They found no significant difference among the three levels with an experiment in a cylindri- cal 3D display.

Original: Using gaze to convey pointing direction within a spherical display has also been shown to be effective [25,33,48].
Revised: Using gaze to convey pointing direction within a spherical display has also been shown to be effective [25,33,48].

Original: The research listed above is mostly concerned with telepresence.
Revised: The research listed above is mostly concerned with telepresence.

Original: That is, the remote person is represented by an avatar or captured using cameras to realize remote collaboration.
Revised: That is, the remote person is represented by an avatar or captured using cameras to realize remote collaboration.

Original: By contrast, we are using the IVA to perform pointing.
Revised: By contrast, we are using the IVA to perform pointing.

Original: In this context, the IVA is regarded as a social entity to mimic human intelligence [32] and work with a person.
Revised: In this context, the IVA is regarded as a social entity to mimic human intelligence [32] and work with a person.

Original: Unlike pointing in telepresence, designing the
Revised: Unlike pointing in telepresence, designing the

Original: IVA’s pointing gestures provides more possibilities to improve users’ perception of pointing as the pointing behaviours do not have to be exactly human-like.
Revised: IVA’s pointing gestures provides more possibilities to improve users’ perception of pointing as the pointing behaviours do not have to be exactly human-like.

Original: Thus, for our design, we have the opportunity to design the IVA’s pointing gestures not completely the same as humans.
Revised: Thus, for our design, we have the opportunity to design the IVA’s pointing gestures not completely the same as humans.

Original: This enables us to remove the eye-fingertip alignment in the IVA as suggested in Section 2.2.
Revised: This enables us to remove the eye-fingertip alignment in the IVA as suggested in Section 2.2.

Original: The complete IVA design is discussed in the following Section 3.
Revised: The complete IVA design is discussed in the following Section 3.

Original: 3 D ESIGN F ACTORS
Revised: 3 D ESIGN F ACTORS

Original: This section elaborates on the design factors to enable our IVA to point as accurately as possible, including the situated display , IVA appearance and pointing gesture strategies.
Revised: This section elaborates on the design factors to enable our IVA to point as accurately as possible, including the situated display , IVA appearance and pointing gesture strategies.

Original: 3.1 Situated Display
Revised: 3.1 Situated Display

Original: We used a spherical FTVR display for IVA due to the following reasons.
Revised: We used a spherical FTVR display for IVA due to the following reasons.

Original: First, FTVR displays are situated in the real world which enables the IVA to point from the virtual environment to locations in the real world.
Revised: First, FTVR displays are situated in the real world which enables the IVA to point from the virtual environment to locations in the real world.

Original: Alternative approaches, such as immersive headset displays, only support pointing within the virtual environment where the IVA is situated.
Revised: Alternative approaches, such as immersive headset displays, only support pointing within the virtual environment where the IVA is situated.

Original: Though AR displays provide the see-through feature that can get similar effects, these systems lack the tangible nature of having a volumetric display that is part of the real world.
Revised: Though AR displays provide the see-through feature that can get similar effects, these systems lack the tangible nature of having a volumetric display that is part of the real world.

Original: FTVR displays also provide motion parallax and stereoscopic cues, which are important in interpreting pointing gestures [33].
Revised: FTVR displays also provide motion parallax and stereoscopic cues, which are important in interpreting pointing gestures [33].

Original: The spherical shape has been found to provide better depth and size perception compared to a planar counterpart [61].
Revised: The spherical shape has been found to provide better depth and size perception compared to a planar counterpart [61].

Original: Spherical screens also showed better task performance in perceiving gaze direction compared to planar screens [26,48].
Revised: Spherical screens also showed better task performance in perceiving gaze direction compared to planar screens [26,48].

Original: As perceiving pointing gestures depends on multiple aspects of visual perception such as depth and orientation perception, it is promising to use spherical FTVR displays to improve the pointing perception.
Revised: As perceiving pointing gestures depends on multiple aspects of visual perception such as depth and orientation perception, it is promising to use spherical FTVR displays to improve the pointing perception.

Original: 3.2 IVA Appearance
Revised: 3.2 IVA Appearance

Original: The state of the art in photo-realistic representations for IVAs is subject to the Uncanny Valley [45]: a high degree of realism does not necessarily lead to positive evaluations.
Revised: The state of the art in photo-realistic representations for IVAs is subject to the Uncanny Valley [45]: a high degree of realism does not necessarily lead to positive evaluations.

Original: Considering this effect, Schneider et al.
Revised: Considering this effect, Schneider et al.

Original: [54] suggest to use a non-human appearance with the ability to behave like a human.
Revised: [54] suggest to use a non-human appearance with the ability to behave like a human.

Original: Following this suggestion, we chose a Japanese female cartoon character as our IVA to avoid the negative feelings caused by a human-like appearance while supporting human- like behaviors.
Revised: Following this suggestion, we chose a Japanese female cartoon character as our IVA to avoid the negative feelings caused by a human-like appearance while supporting human- like behaviors.

Original: Our IVA’s appearance is designed with large eyes and small nose (Figure 3) to provide the characteristic of the baby schema [40], which could induce a pleasurable feeling [27].
Revised: Our IVA’s appearance is designed with large eyes and small nose (Figure 3) to provide the characteristic of the baby schema [40], which could induce a pleasurable feeling [27].

Original: 3.3 Pointing Gestures
Revised: 3.3 Pointing Gestures

Original: We designed our IVA to point following the arm vector (Figure 2 c-1) instead of the eye-fingertip alignment (Figure 2 c-2) to avoid potential perceptual ambiguity.
Revised: We designed our IVA to point following the arm vector (Figure 2 c-1) instead of the eye-fingertip alignment (Figure 2 c-2) to avoid potential perceptual ambiguity.

Original: As discussed in Section 2.2, humans commonly point to where they are looking by aligning their fingertip with the gaze of their dominant eye [7,28] (Figure 2 c-2).
Revised: As discussed in Section 2.2, humans commonly point to where they are looking by aligning their fingertip with the gaze of their dominant eye [7,28] (Figure 2 c-2).

Original: When it comes to perceiving others’ pointing, this might introduce ambiguity because the location followed by the arm vector is different from the actual target location followed by the eye-fingertip line.
Revised: When it comes to perceiving others’ pointing, this might introduce ambiguity because the location followed by the arm vector is different from the actual target location followed by the eye-fingertip line.

Original: Previous work [7] found that participants exhibited a perceptual bias towards the upside of the target, potentially because of this ambiguity.
Revised: Previous work [7] found that participants exhibited a perceptual bias towards the upside of the target, potentially because of this ambiguity.

Original: Therefore, rather than design IVAs to point the same way as humans commonly do (i e., eye-fingertip alignment), we instead remove the eye-fingertip alignment in the design of IVA’s pointing gestures, that is, the arm vector directly points at targets (Figure 2 c-1).
Revised: Therefore, rather than design IVAs to point the same way as humans commonly do (i e., eye-fingertip alignment), we instead remove the eye-fingertip alignment in the design of IVA’s pointing gestures, that is, the arm vector directly points at targets (Figure 2 c-1).

Original: Our expectation is that this approach will mitigate the perceptual errors of eye-fingertip alignment and result in a perceptually accurate IVA pointing gesture.
Revised: Our expectation is that this approach will mitigate the perceptual errors of eye-fingertip alignment and result in a perceptually accurate IVA pointing gesture.

Original: For pointing cues, previous research has found that the orientation of the pointer’s eyes, head and hand are used as visual cues for an observer to interpret a pointing gesture [28,33].
Revised: For pointing cues, previous research has found that the orientation of the pointer’s eyes, head and hand are used as visual cues for an observer to interpret a pointing gesture [28,33].

Original: Prior work [60] has found that the hand cue alone provides accurate pointing perception but with a loss of naturalness.
Revised: Prior work [60] has found that the hand cue alone provides accurate pointing perception but with a loss of naturalness.

Original: In our study, we decide to include all the pointing cues, i.e., eyes, head and hand orientations, to promote accurate and natural perception.
Revised: In our study, we decide to include all the pointing cues, i.e., eyes, head and hand orientations, to promote accurate and natural perception.

Original: In summary, we design our IVA to point with an outstretched arm, eyes and head facing the target without the eye-fingertip alignment; thus, all cues are consistently directing attention to the same location.
Revised: In summary, we design our IVA to point with an outstretched arm, eyes and head facing the target without the eye-fingertip alignment; thus, all cues are consistently directing attention to the same location.

Original: 4 E XPERIMENT
Revised: 4 E XPERIMENT

Original: The goal of our experiment is to assess how accurately our IVA can point into the real world.
Revised: The goal of our experiment is to assess how accurately our IVA can point into the real world.

Original: With a real person’s natural pointing as the baseline, we measured how accurately a human observer can interpret the pointing of our IVA or the real person to a physical location.
Revised: With a real person’s natural pointing as the baseline, we measured how accurately a human observer can interpret the pointing of our IVA or the real person to a physical location.

Original: In doing so, we lay the foundation for the design of IVAs with pointing and shed light on future studies about the contribution of the individual design factor.
Revised: In doing so, we lay the foundation for the design of IVAs with pointing and shed light on future studies about the contribution of the individual design factor.

Original: 4.1 Participants
Revised: 4.1 Participants

Original: Thirty-six participants (19 females and 17 males) aged between 21 and 30 were recruited from a local university to participate in the study with compensation of a $10 gift card.
Revised: Thirty-six participants (19 females and 17 males) aged between 21 and 30 were recruited from a local university to participate in the study with compensation of a $10 gift card.

Original: All had normal or corrected-to-normal vision.
Revised: All had normal or corrected-to-normal vision.

Original: 4.2 Apparatus
Revised: 4.2 Apparatus

Original: We set up the experiment using a situated 24-inch spherical display (Figure 3) which renders the IVA, and a flat fabric projector screen which renders target area.
Revised: We set up the experiment using a situated 24-inch spherical display (Figure 3) which renders the IVA, and a flat fabric projector screen which renders target area.

Original: With four stereo projectors rear projecting onto the spherical surface, we adopted an automated camera-based multi-projector calibration technique [63] to enable a 360-degree seamless image with 1-2 millimeter accuracy.
Revised: With four stereo projectors rear projecting onto the spherical surface, we adopted an automated camera-based multi-projector calibration technique [63] to enable a 360-degree seamless image with 1-2 millimeter accuracy.

Original: The projectors are
Revised: The projectors are

Original: Optoma ML750ST with 1024 × 768 pixel resolution and a frame rate of 120 Hz.
Revised: Optoma ML750ST with 1024 × 768 pixel resolution and a frame rate of 120 Hz.

Original: With an NVIDIA Quadro K5200 graphics card, a host computer sends rendering content to the projectors.
Revised: With an NVIDIA Quadro K5200 graphics card, a host computer sends rendering content to the projectors.

Original: Our IVA was rendered using Unity3D and MikuMikuDance [31] model from DeviantArt [50].
Revised: Our IVA was rendered using Unity3D and MikuMikuDance [31] model from DeviantArt [50].

Original: We used an OptiTrack ™ to track the passive markers attached to the shutter glasses for head tracking.
Revised: We used an OptiTrack ™ to track the passive markers attached to the shutter glasses for head tracking.

Original: We used a pattern-based viewpoint calibration [56] that computed a viewpoint registration with an average angular error of less than one degree.
Revised: We used a pattern-based viewpoint calibration [56] that computed a viewpoint registration with an average angular error of less than one degree.

Original: Viewers gain perspective-corrected images with stereo rendering coupled with the synchronized shutter glasses.
Revised: Viewers gain perspective-corrected images with stereo rendering coupled with the synchronized shutter glasses.

Original: The total latency is between 10-20 msec [22].
Revised: The total latency is between 10-20 msec [22].

Original: With a resolution of 34 .
Revised: With a resolution of 34 .

Original: 58 ppi , the display provides various 3D depth cues such as motion parallax and stereoscopic cues [62].
Revised: 58 ppi , the display provides various 3D depth cues such as motion parallax and stereoscopic cues [62].

Original: An Optoma ML750ST projector with 1024 × 768 pixel resolution was used to display an 80 cm × 80 cm target area on a flat fabric projector screen.
Revised: An Optoma ML750ST projector with 1024 × 768 pixel resolution was used to display an 80 cm × 80 cm target area on a flat fabric projector screen.

Original: The grid content and target indicator were created by Unity3D.
Revised: The grid content and target indicator were created by Unity3D.

Original: 4.3 Human and IVA Pointing
Revised: 4.3 Human and IVA Pointing

Original: As a baseline, an independent real person (RP) was hired to be the pointer.
Revised: As a baseline, an independent real person (RP) was hired to be the pointer.

Original: The dominant hand and eye of our RP are both on the right side.
Revised: The dominant hand and eye of our RP are both on the right side.

Original: To capture the specific natural human pointing as the baseline, RP was not instructed about the specific manner about pointing gestures but just asked to point as accurately as possible with head, eyes and outstretched arm.
Revised: To capture the specific natural human pointing as the baseline, RP was not instructed about the specific manner about pointing gestures but just asked to point as accurately as possible with head, eyes and outstretched arm.

Original: Both RP and IVA used the left arm to point to the targets in the left region and the right arm for targets in the center or right region.
Revised: Both RP and IVA used the left arm to point to the targets in the left region and the right arm for targets in the center or right region.

Original: In practice, most IVAs are rendered in relatively small displays such as home assistant systems [1, 11, 20].
Revised: In practice, most IVAs are rendered in relatively small displays such as home assistant systems [1, 11, 20].

Original: The size difference between IVA and RP makes it challenging to make a fair comparison on the pointing perception.
Revised: The size difference between IVA and RP makes it challenging to make a fair comparison on the pointing perception.

Original: To characterize the potential effect of the size difference, we include two viewing conditions in our study: SameDis and SameRet (Figure 4).
Revised: To characterize the potential effect of the size difference, we include two viewing conditions in our study: SameDis and SameRet (Figure 4).

Original: In SameDis, the IVA and RP are placed at the same observation distance from the participant.
Revised: In SameDis, the IVA and RP are placed at the same observation distance from the participant.

Original: In this condition, the retina image of IVA is smaller than RP with the arm length of IVA and RP as 30 .
Revised: In this condition, the retina image of IVA is smaller than RP with the arm length of IVA and RP as 30 .

Original: 5 cm and 68 cm respectively.
Revised: 5 cm and 68 cm respectively.

Original: In SameRet, the retina sizes of IVA and RP are the same by moving RP 56 cm further away from the participant, resulting in the same angular size of the arm length in IVA and RP.
Revised: In SameRet, the retina sizes of IVA and RP are the same by moving RP 56 cm further away from the participant, resulting in the same angular size of the arm length in IVA and RP.

Original: The viewing condition is designed based on previous study that found the task performance of visual reasoning did not vary as long as the retinal image is unchanged, demonstrated through an experiment with a larger display placed farther than a smaller display [14].
Revised: The viewing condition is designed based on previous study that found the task performance of visual reasoning did not vary as long as the retinal image is unchanged, demonstrated through an experiment with a larger display placed farther than a smaller display [14].

Original: However, moving RP away may introduce potential experimental bias by increasing the viewing distance.
Revised: However, moving RP away may introduce potential experimental bias by increasing the viewing distance.

Original: We included both conditions (same retinal size & same viewing distance) to see what impact the size factor has.
Revised: We included both conditions (same retinal size & same viewing distance) to see what impact the size factor has.

Original: 4.4 Experimental Design
Revised: 4.4 Experimental Design

Original: We followed a 2 × 2 × 2 mixed design with one between-subjects variable ( C1 ) and two within-subjects variables ( C2, C3 ):
Revised: We followed a 2 × 2 × 2 mixed design with one between-subjects variable ( C1 ) and two within-subjects variables ( C2, C3 ):

Original: • C

Revised: • C

Original: The Viewing condition, which could be Same Retinal Size (SameRet) or Same Distance (SameDis).
Revised: The Viewing condition, which could be Same Retinal Size (SameRet) or Same Distance (SameDis).

Original: In SameDis, the viewing distances in RP and IVA are the same.
Revised: In SameDis, the viewing distances in RP and IVA are the same.

Original: In SameRet, the retinal sizes are the same by placing RP 56 cm farther from the participant compared to IVA (Figure 4).
Revised: In SameRet, the retinal sizes are the same by placing RP 56 cm farther from the participant compared to IVA (Figure 4).

Original: • C2 Pointer which could be Intelligent Virtual Agent (IVA) or Real Person (RP).
Revised: • C2 Pointer which could be Intelligent Virtual Agent (IVA) or Real Person (RP).

Original: • C3 Distance which could be near or far.
Revised: • C3 Distance which could be near or far.

Original: The distance between the participant and target area is 70 cm in near and 210 cm in far.
Revised: The distance between the participant and target area is 70 cm in near and 210 cm in far.

Original: We designed C1 as a between-subjects variable to avoid learning and transfer across different viewing conditions.
Revised: We designed C1 as a between-subjects variable to avoid learning and transfer across different viewing conditions.

Original: We randomly and equally divided 36 participants into 2 groups.
Revised: We randomly and equally divided 36 participants into 2 groups.

Original: One group went through SameRet and the other did in SameDis.
Revised: One group went through SameRet and the other did in SameDis.

Original: Each group went through the levels of C2 × C3 .
Revised: Each group went through the levels of C2 × C3 .

Original: The order of C2 and C3 was fully counterbalanced.
Revised: The order of C2 and C3 was fully counterbalanced.

Original: Wemeasurederror and error bias in the horizontal and vertical dimensions, suggested by prior study that has found systematic bias particularly in the vertical direction [7,19].
Revised: Wemeasurederror and error bias in the horizontal and vertical dimensions, suggested by prior study that has found systematic bias particularly in the vertical direction [7,19].

Original: We collected subjective data through a post-study interview.
Revised: We collected subjective data through a post-study interview.

Original: The quantitative metrics are as follows:
Revised: The quantitative metrics are as follows:

Original: • Horizontal & Vertical Error , defined as the Euclidean distance between the actual target location and participants’ perceived location along the corresponding axis.
Revised: • Horizontal & Vertical Error , defined as the Euclidean distance between the actual target location and participants’ perceived location along the corresponding axis.

Original: • Horizontal & Vertical Error Bias , computed by subtracting the actual position from the perceived location.
Revised: • Horizontal & Vertical Error Bias , computed by subtracting the actual position from the perceived location.

Original: A positive value indicates an estimation to the right or above the true locations, respectively.
Revised: A positive value indicates an estimation to the right or above the true locations, respectively.

Original: 4.5 Task
Revised: 4.5 Task

Original: In each trial, participants observed the pointing performed by IVA or RP and reported the pointing position by clicking where they believe the IVA or RP was pointing using a mouse.
Revised: In each trial, participants observed the pointing performed by IVA or RP and reported the pointing position by clicking where they believe the IVA or RP was pointing using a mouse.

Original: They were asked to prior- itize accuracy over speed.
Revised: They were asked to prior- itize accuracy over speed.

Original: The pointing positions are located within an 80 cm × 80 cm square projected onto a fabric projector screen as the target area placed beside participants (Figure 4).
Revised: The pointing positions are located within an 80 cm × 80 cm square projected onto a fabric projector screen as the target area placed beside participants (Figure 4).

Original: Early pilot of this task has shown that the task might be too difficult due to the lack of reference in a blank background.
Revised: Early pilot of this task has shown that the task might be too difficult due to the lack of reference in a blank background.

Original: Therefore we provided a relatively dense 40 × 40 line grid as the target background (Figure 4).
Revised: Therefore we provided a relatively dense 40 × 40 line grid as the target background (Figure 4).

Original: 4.6 Procedure
Revised: 4.6 Procedure

Original: Participants started by filling out a consent form followed by verbal explanations of the experiment.
Revised: Participants started by filling out a consent form followed by verbal explanations of the experiment.

Original: Participants were asked to sit on an adjustable chair (Figure 3) to ensure the horizontal alignment of their shoulder and the pointer’s shoulder in both IVA and RP.
Revised: Participants were asked to sit on an adjustable chair (Figure 3) to ensure the horizontal alignment of their shoulder and the pointer’s shoulder in both IVA and RP.

Original: They were seated by the right side of the pointer (Figure 4).
Revised: They were seated by the right side of the pointer (Figure 4).

Original: The distance between the participant and the target area is 70 cm in near, andcm in far, which are chosen to represent the proximal pointing in the near distance and approximate the distal pointing [53] constrained by the experimental room.
Revised: The distance between the participant and the target area is 70 cm in near, andcm in far, which are chosen to represent the proximal pointing in the near distance and approximate the distal pointing [53] constrained by the experimental room.

Original: Each participant was provided with a mouse and a clipboard to hold it.
Revised: Each participant was provided with a mouse and a clipboard to hold it.

Original: They were instructed to click where they believe the IVA or
Revised: They were instructed to click where they believe the IVA or

Original: RP was pointing by prioritizing accuracy over speed.
Revised: RP was pointing by prioritizing accuracy over speed.

Original: With a total of 4 conditions (IVA vs RP, Near vs Far), each contains 20 trials at different locations with the first 5 provided as practice located at left middle, right middle, top middle, bottom middle and center to illustrate the entire region.
Revised: With a total of 4 conditions (IVA vs RP, Near vs Far), each contains 20 trials at different locations with the first 5 provided as practice located at left middle, right middle, top middle, bottom middle and center to illustrate the entire region.

Original: Participants were told the actual location in the practice trials.
Revised: Participants were told the actual location in the practice trials.

Original: In the formal trials, the locations of targets were randomly generated and can be any location inside the target area.
Revised: In the formal trials, the locations of targets were randomly generated and can be any location inside the target area.

Original: To avoid cross-talk with previous targets serving as a reference, participants were instructed to close their eyes between trials.
Revised: To avoid cross-talk with previous targets serving as a reference, participants were instructed to close their eyes between trials.

Original: When the participant was ready, the IVA pointed to random loca- tions inside the target area, controlled by the experimenter using a keyboard, whereas RP performed the pointing gesture using a visi- ble random target while the participant had their eyes closed.
Revised: When the participant was ready, the IVA pointed to random loca- tions inside the target area, controlled by the experimenter using a keyboard, whereas RP performed the pointing gesture using a visi- ble random target while the participant had their eyes closed.

Original: The dominant hand and eye of our RP are both on the right side.
Revised: The dominant hand and eye of our RP are both on the right side.

Original: Both IVA and RP used the left arm to point to the targets located in the left region and the right arm for targets in the center or right region.
Revised: Both IVA and RP used the left arm to point to the targets located in the left region and the right arm for targets in the center or right region.

Original: When the gesture was ready, the reference target for RP disappeared and participants were asked to open their eyes to perform the task.
Revised: When the gesture was ready, the reference target for RP disappeared and participants were asked to open their eyes to perform the task.

Original: The IVA and RP held the gesture until the participant had finished the click and said “okay.”
Revised: The IVA and RP held the gesture until the participant had finished the click and said “okay.”

Original: No other communication was provided between participants and RP.
Revised: No other communication was provided between participants and RP.

Original: Once all conditions were completed, a follow-up interview was conducted to collect participants’ subjective preference between IVA and RP on the easiness to perceive pointing and the difference between the perceived and actual pointed location.
Revised: Once all conditions were completed, a follow-up interview was conducted to collect participants’ subjective preference between IVA and RP on the easiness to perceive pointing and the difference between the perceived and actual pointed location.

Original: We also asked the pointing cues that they referred to in the task.
Revised: We also asked the pointing cues that they referred to in the task.

Original: The study took approximately 30-40 min to complete.
Revised: The study took approximately 30-40 min to complete.

Original: 4.7 Data Analysis
Revised: 4.7 Data Analysis

Original: We conducted a mixed ANOVA with C1 Viewing as a between- subjects factor, C2 Pointer and as C3 Distance as within-subjects factors.
Revised: We conducted a mixed ANOVA with C1 Viewing as a between- subjects factor, C2 Pointer and as C3 Distance as within-subjects factors.

Original: Significance values were reported in brackets for p < .
Revised: Significance values were reported in brackets for p < .

Original: 05 ( ∗ ) , p < .
Revised: 05 ( ∗ ) , p < .

Original: 01 ( ∗∗ ) , and p < .
Revised: 01 ( ∗∗ ) , and p < .

Original: 001 ( ∗ ∗ ∗ ) respectively.
Revised: 001 ( ∗ ∗ ∗ ) respectively.

Original: Numbers in brackets indicate mean ( M ) and standard error ( SE ) for each re- spective measurement.
Revised: Numbers in brackets indicate mean ( M ) and standard error ( SE ) for each re- spective measurement.

Original: The post-hoc analysis was conducted using pairwise t-tests with Bonferroni corrections.
Revised: The post-hoc analysis was conducted using pairwise t-tests with Bonferroni corrections.

Original: 4.8 Results 4.8.1 Error
Revised: 4.8 Results 4.8.1 Error

Original: With all assumptions met, we used a 2 × 2 × 2 mixed-model ANOVA ( Viewing × Pointer × Distance ) on the Horizontal Error and Vertical
Revised: With all assumptions met, we used a 2 × 2 × 2 mixed-model ANOVA ( Viewing × Pointer × Distance ) on the Horizontal Error and Vertical

Original: Error respectively (Figure 5(a)).
Revised: Error respectively (Figure 5(a)).

Original: Horizontal Error :
Revised: Horizontal Error :

Original: We found main effect of Distance for the horizontal error ( F ( 1 , 34 )
Revised: We found main effect of Distance for the horizontal error ( F ( 1 , 34 )

Original: = 69 .
Revised: = 69 .

Original: 16 , p < 0 .
Revised: 16 , p < 0 .

Original: The mean horizontal error in near Distance ( M = 9 . 98 cm , SE = 0 .
Revised: The mean horizontal error in near Distance ( M = 9 . 98 cm , SE = 0 .

Original: 35 cm ) was 26.5% lower (***) than in far ( M = 13 .
Revised: 35 cm ) was 26.5% lower (***) than in far ( M = 13 .

Original: 58 cm , SE = 0 .
Revised: 58 cm , SE = 0 .

Original: 52 cm ).
Revised: 52 cm ).

Original: We did not find main effects of Viewing ( F ( 1 , 34 )
Revised: We did not find main effects of Viewing ( F ( 1 , 34 )

Original: = 0 .
Revised: = 0 .

Original: 44 , p > 0 . 05) and Pointer ( F ( 1 , 34 ) = 0 .
Revised: 44 , p > 0 . 05) and Pointer ( F ( 1 , 34 ) = 0 .

Original: 44 , p > 0 . 05).
Revised: 44 , p > 0 . 05).

Original: No interaction effects were found among factors.
Revised: No interaction effects were found among factors.

Original: Vertical Error :
Revised: Vertical Error :

Original: We found main effects of Pointer ( F ( 1 , 34 ) = 29 .
Revised: We found main effects of Pointer ( F ( 1 , 34 ) = 29 .

Original: 42 , p < 0 .
Revised: 42 , p < 0 .

Original: 001) and Distance ( F ( 1 , 34 )
Revised: 001) and Distance ( F ( 1 , 34 )

Original: = 31 .
Revised: = 31 .

Original: 74 , p < 0 .
Revised: 74 , p < 0 .

Original: 001) for the vertical error.
Revised: 001) for the vertical error.

Original: The mean vertical error in IVA ( M = 10 .
Revised: The mean vertical error in IVA ( M = 10 .

Original: 22 cm , SE = 0 .
Revised: 22 cm , SE = 0 .

Original: 37 cm ) was 28.8% lower (***) than in RP ( M = 14 .
Revised: 37 cm ) was 28.8% lower (***) than in RP ( M = 14 .

Original: 35 cm , SE = 0 .
Revised: 35 cm , SE = 0 .

Original: 56 cm ).
Revised: 56 cm ).

Original: The mean vertical error in near Dis- tance ( M = 11 .
Revised: The mean vertical error in near Dis- tance ( M = 11 .

Original: 11 cm , SE = 0 .
Revised: 11 cm , SE = 0 .

Original: 47 cm ) was 17.5% lower (***) than in far ( M = 13 .
Revised: 47 cm ) was 17.5% lower (***) than in far ( M = 13 .

Original: 46 cm , SE = 0 .
Revised: 46 cm , SE = 0 .

Original: 52 cm ).
Revised: 52 cm ).

Original: We did not find main effect of Viewing ( F ( 1 , 34 )
Revised: We did not find main effect of Viewing ( F ( 1 , 34 )

Original: = 2 . 66 , p > 0 . 05).
Revised: = 2 . 66 , p > 0 . 05).

Original: A two-way interaction effect was observed between Viewing and Pointer ( F ( 1 , 34 )
Revised: A two-way interaction effect was observed between Viewing and Pointer ( F ( 1 , 34 )

Original: = 5 .
Revised: = 5 .

Original: 05 , p < 0 . 05).
Revised: 05 , p < 0 . 05).

Original: A post-hoc analysis of the two-way interaction effect Viewing × Pointer (Figure 5(d)) shows significant difference in vertical error between RP and IVA in both SameRet ( p < 0 .
Revised: A post-hoc analysis of the two-way interaction effect Viewing × Pointer (Figure 5(d)) shows significant difference in vertical error between RP and IVA in both SameRet ( p < 0 .

Original: and SameDis ( p < 0 . 001).
Revised: and SameDis ( p < 0 . 001).

Original: When viewing in SameRet, the mean vertical error in
Revised: When viewing in SameRet, the mean vertical error in

Original: IVA ( M = 10 .
Revised: IVA ( M = 10 .

Original: 47 cm , SE = 0 .
Revised: 47 cm , SE = 0 .

Original: 48 cm ) was 18.7% lower (*) than in RP ( M = 12 .
Revised: 48 cm ) was 18.7% lower (*) than in RP ( M = 12 .

Original: 88 cm , SE = 0 .
Revised: 88 cm , SE = 0 .

Original: 77 cm ).
Revised: 77 cm ).

Original: When viewing in SameDis, the mean vertical error in IVA ( M = 9 . 98 cm , SE = 0 .
Revised: When viewing in SameDis, the mean vertical error in IVA ( M = 9 . 98 cm , SE = 0 .

Original: 57 cm ) was 36.9% lower (***) than in RP ( M = 15 .
Revised: 57 cm ) was 36.9% lower (***) than in RP ( M = 15 .

Original: 81 cm , SE = 0 .
Revised: 81 cm , SE = 0 .

Original: 75 cm ).
Revised: 75 cm ).

Original: The mean vertical error was significantly lower (*) in SameRet ( M = 12 .
Revised: The mean vertical error was significantly lower (*) in SameRet ( M = 12 .

Original: 88 cm , SE = 0 .
Revised: 88 cm , SE = 0 .

Original: 77 cm ) than in SameDis ( M = 15 .
Revised: 77 cm ) than in SameDis ( M = 15 .

Original: 81 cm , SE = 0 .
Revised: 81 cm , SE = 0 .

Original: 75 cm ) in RP ( p < 0 .
Revised: 75 cm ) in RP ( p < 0 .

Original: but not ( p > 0 . 05) in IVA.
Revised: but not ( p > 0 . 05) in IVA.

Original: 4.8.2 Error Bias
Revised: 4.8.2 Error Bias

Original: With all assumptions met, a mixed-model ANOVA was conducted on the Horizontal and Vertical Error Bias respectively.
Revised: With all assumptions met, a mixed-model ANOVA was conducted on the Horizontal and Vertical Error Bias respectively.

Original: The means and 95% CIs and a scatter plot showing the error bias for all participants can be found in Figure 5(b)(c).
Revised: The means and 95% CIs and a scatter plot showing the error bias for all participants can be found in Figure 5(b)(c).

Original: Horizontal Error Bias : We did not find main effects of Pointer ( F ( 1 , 34 )
Revised: Horizontal Error Bias : We did not find main effects of Pointer ( F ( 1 , 34 )

Original: = 3 .
Revised: = 3 .

Original: 17 , p > 0 . 05)
Revised: 17 , p > 0 . 05)

Original: , Distance ( F ( 1 , 34 ) = 2 . 47 , p > 0 . 05 ),
Revised: , Distance ( F ( 1 , 34 ) = 2 . 47 , p > 0 . 05 ),

Original: Viewing ( F ( 1 , 34 ) = 0 .
Revised: Viewing ( F ( 1 , 34 ) = 0 .

Original: 14 , p > 0 . 05)
Revised: 14 , p > 0 . 05)

Original: for the horizontal error bias, or any interaction effects among three factors.
Revised: for the horizontal error bias, or any interaction effects among three factors.

Original: Vertical Error Bias : We found main effect of Pointer ( F ( 1 , 34 ) = 284 .
Revised: Vertical Error Bias : We found main effect of Pointer ( F ( 1 , 34 ) = 284 .

Original: 84 , p < 0 .
Revised: 84 , p < 0 .

Original: 001 ) for the vertical error bias.
Revised: 001 ) for the vertical error bias.

Original: The mean vertical error bias in IVA ( M = − 2 .
Revised: The mean vertical error bias in IVA ( M = − 2 .

Original: 41 cm , SE = 0 .
Revised: 41 cm , SE = 0 .

Original: 73 cm ) was significantly lower ( p < 0 .
Revised: 73 cm ) was significantly lower ( p < 0 .

Original: 001) than in RP ( M = 13 .
Revised: 001) than in RP ( M = 13 .

Original: 47 cm , SE = 0 .
Revised: 47 cm , SE = 0 .

Original: 64 cm ).
Revised: 64 cm ).

Original: We did not find main effects of Distance ( F ( 1 , 34 )
Revised: We did not find main effects of Distance ( F ( 1 , 34 )

Original: = 1 . 66 , p > 0 . 05)
Revised: = 1 . 66 , p > 0 . 05)

Original: , View- ing ( F ( 1 , 34 ) = 2 . 20 , p > 0 . 05), or any interaction effects among three factors.
Revised: , View- ing ( F ( 1 , 34 ) = 2 . 20 , p > 0 . 05), or any interaction effects among three factors.

Original: 4.8.3 Interview Responses
Revised: 4.8.3 Interview Responses

Original: In the post-study interview, we found that most participants took Hand as the major cue in determining the pointing direction of both
Revised: In the post-study interview we found that most participants took Hand as the major cue in determining the pointing direction of both

Original: IVA (55.6%) and RP (61.1%) as shown in Figure 6(a).
Revised: IVA (55.6%) and RP (61.1%) as shown in Figure 6(a).

Original: We collected participants’ subjective preference between IVA and RP on the ease with which to perceive pointing (Figure 6(b)).
Revised: We collected participants’ subjective preference between IVA and RP on the ease with which to perceive pointing (Figure 6(b)).

Original: We found that a large majority of participants (72.2%) chose the IVA in the SameRet condition as the easier one.
Revised: We found that a large majority of participants (72.2%) chose the IVA in the SameRet condition as the easier one.

Original: Since participants were told the actual locations pointed to in the practice trials before each session, we collected subjective data about whether their expected locations are close to the actual ones to understand their perception of pointing (Figure 6(c)).
Revised: Since participants were told the actual locations pointed to in the practice trials before each session, we collected subjective data about whether their expected locations are close to the actual ones to understand their perception of pointing (Figure 6(c)).

Original: 77.8% participants found that the difference between the actual and perceived location was larger in RP compared to IVA, with 72.2% in SameRet and 83.3% in SameDis.
Revised: 77.8% participants found that the difference between the actual and perceived location was larger in RP compared to IVA, with 72.2% in SameRet and 83.3% in SameDis.

Original: 5 D ISCUSSION
Revised: 5 D ISCUSSION

Original: Based on the results, we summarize the following major findings.
Revised: Based on the results, we summarize the following major findings.

Original: We found that participants can perceive accurately where the IVA was pointing in the real world:
Revised: We found that participants can perceive accurately where the IVA was pointing in the real world:

Original: • IVA achieved accurate pointing perception with the horizontal error of 11.58 cm comparable to 11.99 cm of RP and the vertical error of 10.22 cm significantly lower than 14.35 cm of RP.
Revised: • IVA achieved accurate pointing perception with the horizontal error of 11.58 cm comparable to 11.99 cm of RP and the vertical error of 10.22 cm significantly lower than 14.35 cm of RP.

Original: • Participants showed a systematic upward bias of 13.47 cm regardless of Distance in RP but not in IVA.
Revised: • Participants showed a systematic upward bias of 13.47 cm regardless of Distance in RP but not in IVA.

Original: • The Viewing condition did not appear to affect the accuracy difference between IVA and RP.
Revised: • The Viewing condition did not appear to affect the accuracy difference between IVA and RP.

Original: 5.1 Reflections on Design Factors
Revised: 5.1 Reflections on Design Factors

Original: In this section, we discuss the three design factors (pointing gesture, situated display, and IVA appearance) to provide interpretations of our findings in relation to RP as well as suggest future directions.
Revised: In this section, we discuss the three design factors (pointing gesture, situated display, and IVA appearance) to provide interpretations of our findings in relation to RP as well as suggest future directions.

Original: 5.1.1 Pointing Gestures
Revised: 5.1.1 Pointing Gestures

Original: In our study, RP was asked to point as accurately as possible by natu- rally moving their head, eye-gaze, and outstretched arm towards the target.
Revised: In our study, RP was asked to point as accurately as possible by natu- rally moving their head, eye-gaze, and outstretched arm towards the target.

Original: After the experiment, we asked the RP about their pointing and found the RP used eye-fingertip alignment.
Revised: After the experiment, we asked the RP about their pointing and found the RP used eye-fingertip alignment.

Original: This is not surprising, as it is commonly observed in natural human pointing [7,28].
Revised: This is not surprising, as it is commonly observed in natural human pointing [7,28].

Original: However, we found that participants might perceive the pointing gesture in a way different from how RP performed it.
Revised: However, we found that participants might perceive the pointing gesture in a way different from how RP performed it.

Original: This differ- ence between perceiving and performing the pointing gesture may potentially explain the strong upward bias observed in the RP results (Figure 5(b)).
Revised: This differ- ence between perceiving and performing the pointing gesture may potentially explain the strong upward bias observed in the RP results (Figure 5(b)).

Original: To illustrate this bias, consider Figure 7(a): a pointer outstretches its arm to point to a target (green cube) by placing the fingertip on the line joining the dominant eye and the target.
Revised: To illustrate this bias, consider Figure 7(a): a pointer outstretches its arm to point to a target (green cube) by placing the fingertip on the line joining the dominant eye and the target.

Original: If the viewer perceives the pointing direction by following the arm vector extended from the fingertip, there will be a vertical error causing an incorrect position (blue cube) with an upward bias deviating from the actual pointed position (green cube).
Revised: If the viewer perceives the pointing direction by following the arm vector extended from the fingertip, there will be a vertical error causing an incorrect position (blue cube) with an upward bias deviating from the actual pointed position (green cube).

Original: Note that regardless of the actual target position, the vertical error will always be positive (upwards) since the pointer’s shoulder (the origin of the arm vector) is always below their eyes (the origin of eye-fingertip vector).
Revised: Note that regardless of the actual target position, the vertical error will always be positive (upwards) since the pointer’s shoulder (the origin of the arm vector) is always below their eyes (the origin of eye-fingertip vector).

Original: Similarly, there will also be horizontal bias as shown in Figure 7(b).
Revised: Similarly, there will also be horizontal bias as shown in Figure 7(b).

Original: Different from the vertical bias, horizontal bias can be both positive (on the right) and negative (on the left), which could potentially explain that we only observed systematic positive error bias in the vertical direction but not in the horizontal direction in RP (Figure 5(b)).
Revised: Different from the vertical bias, horizontal bias can be both positive (on the right) and negative (on the left), which could potentially explain that we only observed systematic positive error bias in the vertical direction but not in the horizontal direction in RP (Figure 5(b)).

Original: The systematic upward bias of RP (13.47 cm) is consistent with prior work [7] in which they found a mean angular error bias of 2.5 degree above the target equivalent to a mean vertical error bias of 11.26 cm averaged across the viewing distances used in our setup.
Revised: The systematic upward bias of RP (13.47 cm) is consistent with prior work [7] in which they found a mean angular error bias of 2.5 degree above the target equivalent to a mean vertical error bias of 11.26 cm averaged across the viewing distances used in our setup.

Original: In the post-study interview, the majority of participants (61.1% in RP and 55.6% in IVA) reported that they mainly focused on the hand/arm cue as the reference to find the pointing direction (Fig- ure 6(a)).
Revised: In the post-study interview, the majority of participants (61.1% in RP and 55.6% in IVA) reported that they mainly focused on the hand/arm cue as the reference to find the pointing direction (Fig- ure 6(a)).

Original: This is consistent with prior work [38] as they found users might employ an imaginary ray extending from a fingertip to perceive the pointing in a similar referencing task.
Revised: This is consistent with prior work [38] as they found users might employ an imaginary ray extending from a fingertip to perceive the pointing in a similar referencing task.

Original: In addition,
Revised: In addition,

Original: 77.8% (28) participants (Figure 6(c)) reported a large deviation in RP between the actual and perceived location with 16 participants commenting that it was confusing to find that RP pointed higher ver-
Revised: 77.8% (28) participants (Figure 6(c)) reported a large deviation in RP between the actual and perceived location with 16 participants commenting that it was confusing to find that RP pointed higher ver-

Original: tically than expected.
Revised: tically than expected.

Original: By contrast, 19.4% reported the deviation and confusion in IVA.
Revised: By contrast, 19.4% reported the deviation and confusion in IVA.

Original: It indicates that the IVA’s pointing gesture, which is the arm-vector pointing rather than the eye-fingertip alignment, is likely to be more aligned with how the majority perceived the pointing direction.
Revised: It indicates that the IVA’s pointing gesture, which is the arm-vector pointing rather than the eye-fingertip alignment, is likely to be more aligned with how the majority perceived the pointing direction.

Original: Besides the error bias, we also found the vertical error in IVA (10.22 cm) was significantly lower than RP (14.35 cm) as shown in
Revised: Besides the error bias, we also found the vertical error in IVA (10.22 cm) was significantly lower than RP (14.35 cm) as shown in

Original: Figure 5(a), also reflected in participants’ interview responses on the ease of perceiving the pointing of IVA (Figure 6(b)).
Revised: Figure 5(a), also reflected in participants’ interview responses on the ease of perceiving the pointing of IVA (Figure 6(b)).

Original: Without the eye-fingertip alignment, the correct target location would be reached directly by following the arm vector of IVA.
Revised: Without the eye-fingertip alignment, the correct target location would be reached directly by following the arm vector of IVA.

Original: Therefore, we suggest using the arm-vector as the primary cue when designing the pointing gesture of IVA for higher accuracy of pointing perception.
Revised: Therefore, we suggest using the arm-vector as the primary cue when designing the pointing gesture of IVA for higher accuracy of pointing perception.

Original: Our results showed that participants were more accurate horizon- tally than vertically (Figure 5).
Revised: Our results showed that participants were more accurate horizon- tally than vertically (Figure 5).

Original: One potential cause is the difference between horizontal and vertical visual acuity.
Revised: One potential cause is the difference between horizontal and vertical visual acuity.

Original: Previous work found [15,17] that users have better horizontal visual acuity to perceive gaze directions compared to vertical acuity.
Revised: Previous work found [15,17] that users have better horizontal visual acuity to perceive gaze directions compared to vertical acuity.

Original: Another possible explanation is that the arm switch of the pointer might provide a visual cue as to which side the target is located.
Revised: Another possible explanation is that the arm switch of the pointer might provide a visual cue as to which side the target is located.

Original: The left/right arm inherently implies the left/right region, potentially making the task easier horizontally than vertically.
Revised: The left/right arm inherently implies the left/right region, potentially making the task easier horizontally than vertically.

Original: Further experiments are needed to investigate it.
Revised: Further experiments are needed to investigate it.

Original: 5.1.2 Situated Display
Revised: 5.1.2 Situated Display

Original: Our study was conducted using a spherical FTVR display.
Revised: Our study was conducted using a spherical FTVR display.

Original: It is an open question as to how the findings can be applied to other display devices such as non-FTVR 2D monitors and HMDs.
Revised: It is an open question as to how the findings can be applied to other display devices such as non-FTVR 2D monitors and HMDs.

Original: Conventional flat displays, like monitors without using FTVR, lack depth cues such as motion parallax and stereopsis, which are essential for point- ing perception [33].
Revised: Conventional flat displays, like monitors without using FTVR, lack depth cues such as motion parallax and stereopsis, which are essential for point- ing perception [33].

Original: In addition, on a flat surface, the Mona Lisa effect, which describes a phenomenon in which a character’s eyes seem to follow the user irrespective of the user’s position [43], could negatively affect users’ perception of pointing with eye gaze as a pointing cue.
Revised: In addition, on a flat surface, the Mona Lisa effect, which describes a phenomenon in which a character’s eyes seem to follow the user irrespective of the user’s position [43], could negatively affect users’ perception of pointing with eye gaze as a pointing cue.

Original: Flat FTVR displays provide additional depth cues compared to traditional 2D displays.
Revised: Flat FTVR displays provide additional depth cues compared to traditional 2D displays.

Original: The major difference between a flat and spherical FTVR display is the shape factor.
Revised: The major difference between a flat and spherical FTVR display is the shape factor.

Original: We expect it would be difficult to achieve similar results on a flat FTVR display due to two reasons.
Revised: We expect it would be difficult to achieve similar results on a flat FTVR display due to two reasons.

Original: First, existing studies have found that spherical FTVR displays provided better gaze, depth and size perception than a flat counterpart [26,61].
Revised: First, existing studies have found that spherical FTVR displays provided better gaze, depth and size perception than a flat counterpart [26,61].

Original: Perceiving pointing direction depends on the depth and size perception.
Revised: Perceiving pointing direction depends on the depth and size perception.

Original: Another related issue is the vergenceaccommodation conflict (VAC) [57].
Revised: Another related issue is the vergenceaccommodation conflict (VAC) [57].

Original: Although participants in our experiments were required to sit on a fixed chair, we did not constrain their head motion.
Revised: Although participants in our experiments were required to sit on a fixed chair, we did not constrain their head motion.

Original: With a spherical display, they could keep a relatively constant screen distance following a curvature [61].
Revised: With a spherical display, they could keep a relatively constant screen distance following a curvature [61].

Original: While for the flat counterpart, users’ viewing distance to the screen surface would change while moving their head, which might result in a more pronounced VAC.
Revised: While for the flat counterpart, users’ viewing distance to the screen surface would change while moving their head, which might result in a more pronounced VAC.

Original: Future studies are required to investigate these issues and evaluate IVAs’ pointing accuracy within the flat FTVR displays.
Revised: Future studies are required to investigate these issues and evaluate IVAs’ pointing accuracy within the flat FTVR displays.

Original: Forother 3D displays with perspective-corrected and stereo ren- dering, such as a CAVE and HMDs used in AR, we anticipate that similar results may be found depending on the relative importance of each of the other design factors we investigated, i.e. IVA appearance and pointing gesture type.
Revised: Forother 3D displays with perspective-corrected and stereo ren- dering, such as a CAVE and HMDs used in AR, we anticipate that similar results may be found depending on the relative importance of each of the other design factors we investigated, i.e. IVA appearance and pointing gesture type.

Original: Future studies of controlled experiments would be required to understand the effect of individual factors and potentially associate the result with the display factor.
Revised: Future studies of controlled experiments would be required to understand the effect of individual factors and potentially associate the result with the display factor.

Original: 5.1.3 IVA Appearance
Revised: 5.1.3 IVA Appearance

Original: The different appearances between RP and IVA, such as gender, realism and eyes may have some influence on participants’ perception.
Revised: The different appearances between RP and IVA, such as gender, realism and eyes may have some influence on participants’ perception.

Original: Prior research on user preferences for agents’ gender presents contradictory findings and trends, which may be due to user characteristics or context [49].
Revised: Prior research on user preferences for agents’ gender presents contradictory findings and trends, which may be due to user characteristics or context [49].

Original: Regarding realism, RP was reported by four participants to be more familiar and common.
Revised: Regarding realism, RP was reported by four participants to be more familiar and common.

Original: Two participants commented that IVA’s bigger eyes were helpful to judge the direc- tion.
Revised: Two participants commented that IVA’s bigger eyes were helpful to judge the direc- tion.

Original: In contrast, RP’s eye gaze cue was reported to be subtle by three participants, with one indicating it was even harder to discern the change in the horizontal direction.
Revised: In contrast, RP’s eye gaze cue was reported to be subtle by three participants, with one indicating it was even harder to discern the change in the horizontal direction.

Original: Moreover, two participants said that they tried to avoid eye contact in RP, while there was no such concern in IVA.
Revised: Moreover, two participants said that they tried to avoid eye contact in RP, while there was no such concern in IVA.

Original: Besides, previous research showed that users exposed to images of animals with baby schema were more physi- cally tender in their motor behavior and performed better on a task that demanded extreme carefulness [55].
Revised: Besides, previous research showed that users exposed to images of animals with baby schema were more physi- cally tender in their motor behavior and performed better on a task that demanded extreme carefulness [55].

Original: The baby schema of the IVA might have some effect on participants’ performance.
Revised: The baby schema of the IVA might have some effect on participants’ performance.

Original: Future studies could determine the extent to which each aspect contributes to the pointing perception.
Revised: Future studies could determine the extent to which each aspect contributes to the pointing perception.

Original: 5.2 Distance
Revised: 5.2 Distance

Original: Not surprisingly, participants perceived pointing more accurately when targets were closer than farther, no matter whether it is in
Revised: Not surprisingly, participants perceived pointing more accurately when targets were closer than farther, no matter whether it is in

Original: SameRet or SameDis.
Revised: SameRet or SameDis.

Original: With the same target area, farther distance re- sults in a subtler angular change for all the pointing cues (head, eyes and hand).
Revised: With the same target area, farther distance re- sults in a subtler angular change for all the pointing cues (head, eyes and hand).

Original: Three participants also commented that it was hard to extend the arm line to locate the target when farther away.
Revised: Three participants also commented that it was hard to extend the arm line to locate the target when farther away.

Original: However, despite the higher level of difficulty for farther distances, our IVA can still point more accurately than the real person, indicating the effectiveness of our IVA design.
Revised: However, despite the higher level of difficulty for farther distances, our IVA can still point more accurately than the real person, indicating the effectiveness of our IVA design.

Original: It also suggested that users are able to know where an IVA is pointing within a range of distance.
Revised: It also suggested that users are able to know where an IVA is pointing within a range of distance.

Original: Practically, this implies that should an IVA be used as a home assistant or a virtual tutor, it can be situated in a single location and still be able to point to near and far objects while indicating, “It’s over there.”
Revised: Practically, this implies that should an IVA be used as a home assistant or a virtual tutor, it can be situated in a single location and still be able to point to near and far objects while indicating, “It’s over there.”

Original: to provide deictic indications with users.
Revised: to provide deictic indications with users.

Original: 5.3 Viewing Condition
Revised: 5.3 Viewing Condition

Original: We introduced the Viewing condition as a between-subjects factor due to the size difference between IVA and RP.
Revised: We introduced the Viewing condition as a between-subjects factor due to the size difference between IVA and RP.

Original: Our main finding that IVA provides better pointing perception than RP holds both in
Revised: Our main finding that IVA provides better pointing perception than RP holds both in

Original: SameRet and SameDis.
Revised: SameRet and SameDis.

Original: Therefore, incorporating the Viewing con- dition in the study design helps to validate our results.
Revised: Therefore, incorporating the Viewing con- dition in the study design helps to validate our results.

Original: Besides, we found the Viewing condition plays a role in the pointing perception with the interaction effect Viewing × Pointer (Figure 5(d)).
Revised: Besides, we found the Viewing condition plays a role in the pointing perception with the interaction effect Viewing × Pointer (Figure 5(d)).

Original: Adjusting the distance between RP and the participant leads to different retinal sizes and causes the difference in the vertical error between SameRet and SameDis in RP.
Revised: Adjusting the distance between RP and the participant leads to different retinal sizes and causes the difference in the vertical error between SameRet and SameDis in RP.

Original: Note that the difference is only in the vertical error but not in the vertical error bias, indicating that changing the
Revised: Note that the difference is only in the vertical error but not in the vertical error bias, indicating that changing the

Original: Viewing condition did not introduce systematic bias but affected the precision of the pointing perception.
Revised: Viewing condition did not introduce systematic bias but affected the precision of the pointing perception.

Original: One possible explanation is that there might exist an optimal viewing distance and retinal size to perceive the pointing direction by observing the pointer’s posture.
Revised: One possible explanation is that there might exist an optimal viewing distance and retinal size to perceive the pointing direction by observing the pointer’s posture.

Original: Our study focused on the difference between pointers and evaluated one fixed distance or retinal size.
Revised: Our study focused on the difference between pointers and evaluated one fixed distance or retinal size.

Original: Future studies are needed to investigate the potential effect of different viewing distances and retinal sizes on the pointing perception.
Revised: Future studies are needed to investigate the potential effect of different viewing distances and retinal sizes on the pointing perception.

Original: Participants’ comments on the size difference are quite divergent.
Revised: Participants’ comments on the size difference are quite divergent.

Original: In SameDis where the retinal size of IVA is approximately half the size of RP, 5 out of 18 participants commented that IVA’s pointing was easier.
Revised: In SameDis where the retinal size of IVA is approximately half the size of RP, 5 out of 18 participants commented that IVA’s pointing was easier.

Original: They explained that the smaller size of IVA allowed them to perceive a more noticeable change of eyes, hand and head orientation.
Revised: They explained that the smaller size of IVA allowed them to perceive a more noticeable change of eyes, hand and head orientation.

Original: Conversely, 4 out of 18 participants who found RP easier commented that RP’s life-size was more natural to perceive the pointing.
Revised: Conversely, 4 out of 18 participants who found RP easier commented that RP’s life-size was more natural to perceive the pointing.

Original: Similarly in SameRet their comments are also divergent.
Revised: Similarly in SameRet their comments are also divergent.

Original: Four participants preferred IVA’s smaller size whereas two preferred the life-size of RP.
Revised: Four participants preferred IVA’s smaller size whereas two preferred the life-size of RP.

Original: While future studies can quantify individuals’ sensitivity to this factor, we also note that from a practical perspective, our study shows that there is unlikely a one-size-fits-all solution to optimize the size and visual representation of an IVA.
Revised: While future studies can quantify individuals’ sensitivity to this factor, we also note that from a practical perspective, our study shows that there is unlikely a one-size-fits-all solution to optimize the size and visual representation of an IVA.

Original: Thus, allowing users to tailor their IVA’s appearance would be advisable.
Revised: Thus, allowing users to tailor their IVA’s appearance would be advisable.

Original: 6 D ESIGN I MPLICATIONS
Revised: 6 D ESIGN I MPLICATIONS

Original: The main design implication from our study is that with a set of design factors determined, it is feasible to have an IVA point with comparable accuracy to a real person.
Revised: The main design implication from our study is that with a set of design factors determined, it is feasible to have an IVA point with comparable accuracy to a real person.

Original: In our IVA design, we used a spherical FTVR display, rendered a 3D cartoon IVA with humanlike behaviors and applied arm vector pointing instead of the eye- fingertip alignment, which collectively contributes to our IVA’s high pointing accuracy.
Revised: In our IVA design, we used a spherical FTVR display, rendered a 3D cartoon IVA with humanlike behaviors and applied arm vector pointing instead of the eye- fingertip alignment, which collectively contributes to our IVA’s high pointing accuracy.

Original: As the appearance and pointing gesture strategy are not dependent on the display factor, we expect these design choices could be considered in other display devices.
Revised: As the appearance and pointing gesture strategy are not dependent on the display factor, we expect these design choices could be considered in other display devices.

Original: The findings serve as a foundation for designing an IVA to point to the physical world accurately and provide pathways for future studies to precisely quantify the relative contribution of each factor.
Revised: The findings serve as a foundation for designing an IVA to point to the physical world accurately and provide pathways for future studies to precisely quantify the relative contribution of each factor.

Original: We also suggest to provide more cues for perceiving pointing to objects farther away.
Revised: We also suggest to provide more cues for perceiving pointing to objects farther away.

Original: According to our results, when participants were farther from the target, the accuracy of the pointing percep- tion decreased significantly.
Revised: According to our results, when participants were farther from the target, the accuracy of the pointing percep- tion decreased significantly.

Original: Visual cues such as the orientation of the head, hand and eye gaze might not be sufficient to accurately indicate the target.
Revised: Visual cues such as the orientation of the head, hand and eye gaze might not be sufficient to accurately indicate the target.

Original: Additional verbal cues, such as the location or feature description, should be considered to convey the pointing di- rection efficiently, which better resembles human pointing behaviour.
Revised: Additional verbal cues, such as the location or feature description, should be considered to convey the pointing di- rection efficiently, which better resembles human pointing behaviour.

Original: For example, a combination of verbal description, i.e., “it’s on the table over there”, with a pointing gesture can be implemented with
Revised: For example, a combination of verbal description, i.e., “it’s on the table over there”, with a pointing gesture can be implemented with

Original: IVAs.
Revised: IVAs.

Original: A future study could investigate the natural communication mechanisms combining voice and deictic gestures.
Revised: A future study could investigate the natural communication mechanisms combining voice and deictic gestures.

Original: 7 L IMITATIONS AND F UTURE W ORK
Revised: 7 L IMITATIONS AND F UTURE W ORK

Original: We discuss four limitations of our work along with opportunities they present for future research.
Revised: We discuss four limitations of our work along with opportunities they present for future research.

Original: First, we hired one single RP as the baseline pointer.
Revised: First, we hired one single RP as the baseline pointer.

Original: Though we confirmed with RP that his pointing behavior followed the eye-fingertip alignment, future work could use a motion capture system to track the posture and provide some data about the accuracy objectively.
Revised: Though we confirmed with RP that his pointing behavior followed the eye-fingertip alignment, future work could use a motion capture system to track the posture and provide some data about the accuracy objectively.

Original: Further, the RP in the experiment was instructed to point at the same location until the participant said ’OK’.
Revised: Further, the RP in the experiment was instructed to point at the same location until the participant said ’OK’.

Original: Holding pointing for a long duration will have unintentional movements, such as, hand tremor and jitter, which will impact the perception of pointing negatively.
Revised: Holding pointing for a long duration will have unintentional movements, such as, hand tremor and jitter, which will impact the perception of pointing negatively.

Original: The IVA can be designed to hold its posture perfectly still, so does not suffer from unintentional movements.
Revised: The IVA can be designed to hold its posture perfectly still, so does not suffer from unintentional movements.

Original: Though, these human movements may positively impact the feeling of naturalness, which may play a role in mitigating an uncanny valley when designing photo-realistic IVAs.
Revised: Though, these human movements may positively impact the feeling of naturalness, which may play a role in mitigating an uncanny valley when designing photo-realistic IVAs.

Original: Without explicit instructions, the RP pointed naturally in a way with eye-fingertip alignment commonly found in human natural pointing [7,28].
Revised: Without explicit instructions, the RP pointed naturally in a way with eye-fingertip alignment commonly found in human natural pointing [7,28].

Original: Our primary goal for the study was to establish that users can perceive where a carefully designed IVA is pointing.
Revised: Our primary goal for the study was to establish that users can perceive where a carefully designed IVA is pointing.

Original: While using an
Revised: While using an

Original: RP baseline illustrated some potential avenues of research to quantify the differences in pointing between IVAs and real people, our study was not designed to do so.
Revised: RP baseline illustrated some potential avenues of research to quantify the differences in pointing between IVAs and real people, our study was not designed to do so.

Original: For example, natural human pointing has a range of variations of pointing gestures and strategies that are employed.
Revised: For example, natural human pointing has a range of variations of pointing gestures and strategies that are employed.

Original: We believe future studies can pursue with multiple RPs spanning a range of strategies, which would help establish the robustness of IVA pointing relative to human pointing, and define the lower and upper bounds of IVA/RP differences to provide additional insight into different design approaches for IVA pointing gestures and appearance.
Revised: We believe future studies can pursue with multiple RPs spanning a range of strategies, which would help establish the robustness of IVA pointing relative to human pointing, and define the lower and upper bounds of IVA/RP differences to provide additional insight into different design approaches for IVA pointing gestures and appearance.

Original: Second,despite providing head tracking and depth cues, FTVR displays still have many technical and perceptual limitations, e.g., lower resolution and fewer depth cues than in reality.
Revised: Second,despite providing head tracking and depth cues, FTVR displays still have many technical and perceptual limitations, e.g., lower resolution and fewer depth cues than in reality.

Original: These con- straints may affect participants’ accuracy.
Revised: These con- straints may affect participants’ accuracy.

Original: Two participants pointed out that IVA lacked depth information (e.g., shadows and lighting).
Revised: Two participants pointed out that IVA lacked depth information (e.g., shadows and lighting).

Original: However, all of their quantitative data still suggests a higher accuracy in IVA than in the RP baseline.
Revised: However, all of their quantitative data still suggests a higher accuracy in IVA than in the RP baseline.

Original: This indicates that our display’s constraints did not appear to have a notable negative impact on participants’ performance.
Revised: This indicates that our display’s constraints did not appear to have a notable negative impact on participants’ performance.

Original: The effect of display quality characteristics on the perception of pointing should be identified with further user studies.
Revised: The effect of display quality characteristics on the perception of pointing should be identified with further user studies.

Original: Third, the design of an IVA involves many factors.
Revised: Third, the design of an IVA involves many factors.

Original: In this paper, we focused on using a situated spherical FTVR display, a cartoon
Revised: In this paper, we focused on using a situated spherical FTVR display, a cartoon

Original: IVA appearance and arm-vector pointing gestures.
Revised: IVA appearance and arm-vector pointing gestures.

Original: We demonstrated that these factors were sufficient for the IVA to point with comparable accuracy to a real person.
Revised: We demonstrated that these factors were sufficient for the IVA to point with comparable accuracy to a real person.

Original: Future work will draw attention to controlled experiments for each of the design factors to demonstrate their effects and the degree of individual’s sensitivity to the cues that we observed.
Revised: Future work will draw attention to controlled experiments for each of the design factors to demonstrate their effects and the degree of individual’s sensitivity to the cues that we observed.

Original: For example, to precisely quantify the effect of the eye-fingertip alignment, we can have an IVA point with eye-fingertip alignment to compare with the current design.
Revised: For example, to precisely quantify the effect of the eye-fingertip alignment, we can have an IVA point with eye-fingertip alignment to compare with the current design.

Original: Through studying different pointing configurations, we can create a set of configurable IVA characters that individuals can personalize to optimize their interactions with the IVA.
Revised: Through studying different pointing configurations, we can create a set of configurable IVA characters that individuals can personalize to optimize their interactions with the IVA.

Original: Last, gesture and language are highly integrated components in interpersonal conversation [8,21,42].
Revised: Last, gesture and language are highly integrated components in interpersonal conversation [8,21,42].

Original: Our study provides a foundation for designing IVAs that can point accurately to the real world.
Revised: Our study provides a foundation for designing IVAs that can point accurately to the real world.

Original: However, during a conversation, people do not rely on pointing gestures exclusively [7].
Revised: However, during a conversation, people do not rely on pointing gestures exclusively [7].

Original: Typically, they will rely differently and flexibly on gestural or verbal means [6].
Revised: Typically, they will rely differently and flexibly on gestural or verbal means [6].

Original: Thus, a future step will concentrate on the role of pointing gestures with verbal cues given to establish joint attention with the IVA.
Revised: Thus, a future step will concentrate on the role of pointing gestures with verbal cues given to establish joint attention with the IVA.

Original: 8 C ONCLUSION
Revised: 8 C ONCLUSION

Original: In this paper, we proposed an IVA with design factors including a situated display, appearance, and pointing gesture strategy to investigate whether it is possible to have an IVA point accurately into the real world.
Revised: In this paper, we proposed an IVA with design factors including a situated display, appearance, and pointing gesture strategy to investigate whether it is possible to have an IVA point accurately into the real world.

Original: Using a spherical FTVR display, we conducted a study to measure the IVA’s pointing accuracy while comparing to a natural human pointing baseline.
Revised: Using a spherical FTVR display, we conducted a study to measure the IVA’s pointing accuracy while comparing to a natural human pointing baseline.

Original: In the study, the IVA’s pointing accuracy was determined by having participants estimate where they perceive the IVA is pointing in the real world.
Revised: In the study, the IVA’s pointing accuracy was determined by having participants estimate where they perceive the IVA is pointing in the real world.

Original: The participants also estimated where a real person was pointing using the same experimental setup for comparison and discussion of the different design factors.
Revised: The participants also estimated where a real person was pointing using the same experimental setup for comparison and discussion of the different design factors.

Original: Our results show that participants perceived the IVA’s pointing into the real world with comparable accuracy to the real person.
Revised: Our results show that participants perceived the IVA’s pointing into the real world with comparable accuracy to the real person.

Original: Specifically, the IVA outperformed the real person in the vertical dimension and yielded the same level of accuracy horizontally.
Revised: Specifically, the IVA outperformed the real person in the vertical dimension and yielded the same level of accuracy horizontally.

Original: We discussed design factors that likely contributed to the success of the IVA pointing accuracy, and suggested directions for future studies to provide accurate pointing perception.
Revised: We discussed design factors that likely contributed to the success of the IVA pointing accuracy, and suggested directions for future studies to provide accurate pointing perception.

Original: Our results for the human pointing baseline are consistent with previous literature, showing that participants mainly focus on the pointer’s hand, which leads to a bias when interpreting a real person’s pointing direction.
Revised: Our results for the human pointing baseline are consistent with previous literature, showing that participants mainly focus on the pointer’s hand, which leads to a bias when interpreting a real person’s pointing direction.

Original: Particularly, we found participants exhibited a systematic upward bias in the vertical dimension when perceiving the human pointer, which we suspect is due to the ambiguity associated with the eye-fingertip alignment that is commonly employed by people when they point in the real world.
Revised: Particularly, we found participants exhibited a systematic upward bias in the vertical dimension when perceiving the human pointer, which we suspect is due to the ambiguity associated with the eye-fingertip alignment that is commonly employed by people when they point in the real world.

Original: The adjustment afforded by the IVA design to use arm vector pointing is helpful to improve IVA pointing accuracy.
Revised: The adjustment afforded by the IVA design to use arm vector pointing is helpful to improve IVA pointing accuracy.

Original: As voice and visual interfaces for home assistants and other digital assistants are becoming commonly used in daily life, an embodied
Revised: As voice and visual interfaces for home assistants and other digital assistants are becoming commonly used in daily life, an embodied

Original: IVA that can provide gesture cues is expected to enable a more human-like interaction.
Revised: IVA that can provide gesture cues is expected to enable a more human-like interaction.

Original: We demonstrated that a well-designed 3D visual representation of an IVA can be endowed with the capability to point to the real world with comparable accuracy to a real person.
Revised: We demonstrated that a well-designed 3D visual representation of an IVA can be endowed with the capability to point to the real world with comparable accuracy to a real person.

Original: Our work shows how an IVA rendered in a 3D display can provide effective pointing gestures, which could be used in conjunction with a voice interface for natural communication bridging the virtual and the real world.
Revised: Our work shows how an IVA rendered in a 3D display can provide effective pointing gestures, which could be used in conjunction with a voice interface for natural communication bridging the virtual and the real world.

Original: A CKNOWLEDGMENTS
Revised: A CKNOWLEDGMENTS

Original: The authors wish to thank reviewers for their constructive comments and NSERC for funding this project
Revised: The authors wish to thank reviewers for their constructive comments and NSERC for funding this project