This study investigates how partner avatar design affects learning and memory when an avatar serves as a lecturer. Based on earlier research on the environmental context dependency of memory, we hypothesize that the use of diverse partner avatars results in a slower learning rate but better memory retention than that of a constant partner avatar. Accordingly, participants were tasked with memorizing Tagalog-Japanese word pairs. On the first day of the experiment, they repeatedly learned the pairs over six sessions from a partner avatar in an immersive virtual environment. One week later, on the second day of the experiment, they underwent a recall test in a real environment. We employed a between-participants design to compare the following conditions: the varied avatar condition, in which each repetition used a different avatar, and the constant avatar condition, in which the same avatar was used throughout the experiment. Results showed that participants in the varied avatar condition recalled significantly worse during the learning trials on the first day. However, we found no significant difference between conditions in the delayed recall test on the second day. We discuss these effects in relation to the social presence of the partner avatar. This study opens up a novel approach to optimizing the effectiveness of instructor avatars in immersive virtual environments.

Recall impairment in a different environmental context from learning is called context-dependent forgetting. Two learning methods have been proposed to prevent context-dependent forgetting: reinstatement and decontextualization. Reinstatement matches the environmental context between learning and retrieval, whereas decontextualization involves repeated learning in various environmental contexts and eliminates the context dependency of memory. Conventionally, these methods have been validated by switching between physical rooms. However, in this study, we use immersive virtual environments (IVEs) as the environmental context assisted by virtual reality (VR), which is known for its low cost and high reproducibility compared to traditional manipulation. Whereas most existing studies using VR have failed to reveal the reinstatement effect, we test its occurrence using a 360-degree video-based IVE with improved familiarity and realism instead of a computer graphics-based IVE. Furthermore, we are the first to address decontextualization using VR. Our experiment showed that repeated learning in the same constant IVE as retrieval did not significantly reduce forgetting compared to repeated learning in different constant IVEs. Conversely, repeated learning in various IVEs significantly reduced forgetting than repeated learning in constant IVEs. These findings contribute to the design of IVEs for VR-based applications, particularly in educational settings.

This study proposes a new learning method that employs multiple embodied self-avatars during learning, to use the potential benefit of virtual reality (VR) for effective learning and training. In this study, by taking advantage of the benefit of virtual reality (VR), we propose a new learning method that employs multiple embodied self-avatars during learning. Based on the multiple-context effect, which posits that learning in diverse situations can prevent forgetting and enhance memory retention, we conducted a between-participants study under two conditions: the varied avatar condition, in which participants learned sign languages with different self-avatars in six iterations, and the constant avatar condition, in which the same self-avatar was used consistently. We employed sign language as a learning material that naturally draws attention to self-avatars and is suitable for investigating the effects of varying self-avatars. Initially, the varied avatar condition performed worse than the constant avatar condition. However, in a test conducted after one week in the real world, the varied avatar condition showed significantly less forgetting and better retention than the constant avatar condition. Furthermore, our results suggested a positive correlation between the degree of embodiment toward the avatars and the effectiveness of the proposed method. This study presents an innovative design approach for the use of self-avatars in VR-based education.

The methods of displaying virtual agents and avatars as lecturers have been studied in remote lectures and asynchronous education. In this study, we tested the hypothesis that presenting information using multiple virtual avatars facilitates users’ memory performance. In a memory task involving remembering 100 words, we compared a condition where the same avatar narrated all the words to a condition where different avatars each presented 25 words. The results of the online experiment showed no significant differences in the number of words recalled between both conditions. However, we found that switching between avatars significantly aided in recalling the source of information, namely, discerning which avatars read specific words. Furthermore, through an exploratory analysis, we found that using a human avatar resulted in better memory retention than using other avatars (red panda, extraterrestrial being, robot). The participants’ feedback also indicated that the red panda avatar may be perceived favorably and that the quality of lip-syncing was associated with discomfort. These findings are expected to enrich future research on agents and avatars in educational settings.

Advancements in virtual reality technology have facilitated users in freely changing their appearance during communication. Notably, it has become evident that the perceptual and cognitive responses of users vary when their partner uses an animal avatar compared to those when using a human avatar. This study aimed to clarify the effects of partner-avatars on memory through experiments wherein participants were tasked with memorizing the profiles spoken by the partner-avatars. A preliminary experiment validated the assumption that both the animal avatars and the virtual environments could be integrated into processes of profile memory. Subsequently, the primary experiment examined differences in performance in remembering partners’ profiles when the partners were animal avatars versus human avatars. The results showed that the animal avatar condition was marginally inferior to the human avatar condition. Moreover, the perceived intimacy and the presence of others were significantly lower in the animal avatar condition. These findings suggested that interacting with animal avatars may have specific drawbacks in terms of profile memory and engagement in social interactions within virtual environments.

Episodic memory is influenced by environmental contexts, such as location and auditory stimuli. The most well-known effect is the reinstatement effect, which refers to the phenomenon where contextual matching between learning and testing enhances memory retrieval. Previous studies have investigated whether the reinstatement effect can be observed within immersive virtual environments. However, only a limited number of studies have reported a significant reinstatement effect using virtual reality, while most have failed to detect it. In this study, we re-examined the reinstatement effect using 360-degree video-based virtual environments. Specifically, we carefully selected virtual environments to elicit different emotional responses, which has been suggested as a key factor in inducing a robust reinstatement effect in the physical world. Surprisingly, we found a significant reversed reinstatement effect with a large effect size. This counter-intuitive result suggests that contextual congruence does not necessarily enhance memory and may even interfere with it. This outcome may be explained by the retrieval-induced forgetting phenomenon, but further exploration is needed. This finding is particularly important for virtual reality-based, educational applications and highlights the need for a deeper understanding of the complex interactions between memory and contextual cues within virtual environments.

The time elapsed during a virtual reality (VR) experience is estimated to be short. Time estimation, a feeling related to timescales longer than a few seconds, is thought to be related to interoception. The shortening of time estimation may be caused by the VR experience distorting bodily awareness based on interoception; however, the details of this change have not been clarified. The characteristics of avatars are likely to affect bodily awareness. Therefore, based on the hypothesis that bodily awareness during a VR experience is altered by manipulating the avatar’s degree of anthropomorphism, this study investigated the effect of avatar anthropomorphism on bodily awareness and time estimation. In an experiment, participants performed a heartbeat discrimination task and a one-minute time estimation task, in the real world (Real condition), in the virtual world using a human avatar (VR-Human condition), and in the virtual world using a robot avatar (VR-Robot condition). The results showed that the perceived sense of agency was significantly lower in the VR-Human condition than in the VR-Robot condition, and interoceptive accuracy was significantly higher in the VR-Human condition than in the VR-Robot condition. However, there were no differences in time estimation between conditions. These results indicate that it is possible to conduct experiments to manipulate bodily awareness by manipulating the avatar characteristics. These findings can provide insights into understanding the relationship between bodily awareness and time estimation.

Episodic memory incorporates environmental contexts, and memory retrieval is aided by matching the retrieval context to the encoding context. This study tested whether similar context-dependency of memory could be confirmed in virtual environments. Participants learned words in a 360-degree video-based virtual environment depicting either natural or urban landscapes. Immediately, they completed a test in the same virtual environment. After two days, half of the participants underwent a final test with the same context as that on the initial day, whereas the other half underwent it with a different context. Surprisingly, participants tested in a different context exhibited significantly lower forgetting than those tested in the same context, which contradicted our hypothesis.

Virtual reality (VR) is a promising tool for motor skill learning. Previous studies have indicated that observing and following a teacher's movements from a first-person perspective using VR facilitates motor skill learning. Conversely, it has also been pointed out that this learning method makes the learner so strongly aware of the need to follow that it weakens their sense of agency (SoA) for motor skills and prevents them from updating the body schema, thereby preventing long-term retention of motor skills. To address this problem, we propose applying "virtual co-embodiment" to motor skill learning. Virtual co-embodiment is a system in which a virtual avatar is controlled based on the weighted average of the movements of multiple entities. Because users in virtual co-embodiment overestimate their SoA, we hypothesized that learning using virtual co-embodiment with a teacher would improve motor skill retention. In this study, we focused on learning a dual task to evaluate the automation of movement, which is considered an essential element of motor skills. As a result, learning in virtual co-embodiment with the teacher improves motor skill learning efficiency compared with sharing the teacher's first-person perspective or learning alone.

Advances in virtual reality technology have enabled the creation of virtual environments (VEs) with significantly high visual fidelity when compared to real environments (REs). In this study, we use a high-fidelity VE to examine two effects caused by alternating VE and RE experiences: "context-dependent forgetting" and "source-monitoring errors." The former effect is that memories learned in VEs are more easily recalled in VEs than in REs, whereas memories learned in REs are more easily recalled in REs than in VEs. The source-monitoring error is that memories learned in VEs are easily confused with those learned in REs, making discriminating the source of the memory difficult. We hypothesized that the visual fidelity of VEs is responsible for these effects and conducted an experiment using two types of VEs: a high-fidelity VE created using photogrammetry techniques and low-fidelity VE created with primitive shapes and materials. The results show that the high-fidelity VE significantly improved the sense of presence. However, the level of the visual fidelity of the VEs did not show any effect on context-dependent forgetting and source-monitoring errors. Notably, the null results of the context-dependent forgetting between the VE and RE were strongly supported by Bayesian analysis. Thus, we indicate that context-dependent forgetting does not necessarily occur, which will be helpful for VR-based education and training.

Virtual reality helps us learn complex motor skills by providing a situation in which we observe or follow a teacher’s movements from a first-person perspective. However, it has been suggested that if the learners themselves do not behave actively, their body schemes will not be updated and motor skills will be acquired temporarily, but will not be retained in the long term. As a solution to this problem, “co-embodiment” in which two people embody an avatar that reflects the weighted average of their movements was proposed, and it is shown that the user can feel an excessive sense of agency (SoA) even when their control weight is small. From the perspective of motor skill learning, the learner must feel as strong a SoA as possible while performing the exercise as close to the teacher as possible. Therefore, in this study, we propose a method to transitionally change the weights in a situation where co-embodiment is used, such that a strong SoA is felt despite the high weights of control by others. Considering the two-step account of the agency model, which states that the SoA is influenced by context, we tested the hypothesis that an initially strong SoA can maintain the SoA despite a gradually decreased control weight. The experimental results support this hypothesis, and it is expected that the proposed method will enhance the effectiveness of motor skill learning using co-embodiment.