Abstract
As the usage of head-mounted displays (HMD) increases, it is important to establish best usage practices to ensure the appropriate use of Virtual Reality (VR) equipment. Among the factors that can contribute to a better user experience are exposure time, the content type and the gender of the user. This study evaluates the impact of these variables on users' Sense of Presence and Cybersickness when visualising 360 content using HMDs. Two types of 360 content (captured video vs. virtual environment) were evaluated across four different exposure times (1, 3, 5 and 7 min). Regarding Sense of Presence, the results revealed a statistically significant difference for Content Type, Gender, and Content Type x Gender. Regarding Cybersickness, no statistically significant results were found for any of the independent variables. Overall, the results encourage the use of synthesized environments for a female audience; for non-interactive environments, captured environments are more effective than synthesized environments; and exposure time is not a concern for experiences lasting between 1 and 7 min.

Abstract
The traditional attitude towards user interfaces has changed. The Post-WIMP era has brought about novel input modalities such as touch, tangibles or gestures that allow users to manipulate digital contents more intuitively. These novel input modalities make use of the users' innate skills instead of imposing the learning of new interaction techniques. Nonetheless, there has not been a systematic evaluation on how, or if, these interfaces influence the users' performance and/or preference: distinct interfaces may be more or less appropriate regarding different age groups, user profiles, contexts or type of tasks. This work is a preliminary evaluation on whether the users' efficiency is indeed influenced by different input modalities or age. We conducted a target acquisition performance evaluation with 60 subjects to understand how different input modalities influence the speed and accuracy of three specific age groups (children, young adults and older-adults) when dealing with a continuous selection task. Three input modalities were considered to perform the task (mouse, touch and gestures) and the methodology was based on Fitts' law, a target acquisition performance evaluation model. Overall, when comparing movement times amongst the three groups, there are significant differences between age groups regarding the index of performance. We believe our findings may show that indeed the type of input modality used and the user's age could affect one's performance.

Abstract
Tone mapping operators (TMOs) allow the visual appearance of High Dynamic Range (HDR) video to be reproduced on Low Dynamic Range (LDR) displays. While several studies have been made to compare the performance of different TMOs on standard displays, there is only one preliminary study that takes into account the characteristics of Small Screen Devices (SSDs) which are common on mobile platforms that are growing rapidly in popularity. Due to the unique characteristics of mobile devices, the variety of viewing conditions where they are used, and the fact that they are becoming so widespread, it is important to identify what is the best method to deliver HDR video content to these devices. This paper presents an evaluation of HDR video on mobile devices using an HDR display as reference. Six state-of-the-art HDR video tone mappers are evaluated by conducting a psychophysical experiment where participants were asked to rank the tone mappers applied to different HDR video footage. A comparison was made between tone mapped HDR video footage shown on a tablet and an LCD display compared with the same HDR video footage shown simultaneously on an HDR display. This study shows there is a subtle but statistically significant difference in the preference of TMOs between SSD and LDR even though the overall ordering of TMOs is the same across both displays.

Abstract
There is a trend towards the use of Virtual Reality (VR) environments and its evolution has promoted new interaction approaches so there is a need for studying a number of factors that can have impact on its usability. This paper studies the impact of the body position on the usability of VR environments. For the effect, a case study was undertaken based on a bicycle ride that considers two body positions: riding the bicycle seated with the feet on the pedals and hands in the handlebar; and standing with the feet on the ground and the hands on the handlebar. On both cases they had control over the bicycle (steer and brakes). These two body positions were considered as they will allow studying in detail the impact of the different body positions: the first condition mimics the real body position of the depicted scenario while the second condition tests an alternate body position. Results regarding the system's effectiveness have shown an 100% success rate as all participants concluded the task successfully and there were no dropouts. The efficiency results have revealed that the more the participants used the VE the less the number of errors they made and that the completion time differences between the tested conditions were insignificant (> 0.5 seconds). As for satisfaction, participants reported a preference towards the standing position. Furthermore, results reveal that body position has impact on the users' performance but it does not necessarily affect their satisfaction over the virtual experience. © 2016 ACM.

Abstract
Equipment such as head-mounted displays are now available for the average consumer at affordable prices. This promotes the usage of this equipment for content consumption and demonstrations, thus it becomes important to establish the best practices for using this technology, namely guidelines in what concerns the recommended exposure time. Therefore, the purpose of this work is to study the impact of the exposure time on the feeling of presence while watching 360 degrees video using an head-mounted display. The independent variables of the study are the exposure time to the stimuli and gender of participants. There were tested four different exposure times: 1 minute, 3 minutes, 5 minutes and 7 minutes. For measuring presence, it was a Portuguese version of the Igroup Presence Questionnaire (IPQ) which considers also 3 presence subscales: spatial presence, realism and involvement. The results have revealed that there are few statistically significant differences for the given exposure times at the level of the sense of presence, apart from spatial presence and realism subscales, which consistently increased with exposure time for male participants and slightly decreased for female ones. Men always needed longer exposure times (> 1 minute) to report the highest scores, while women had the opposite behaviour, frequently reporting maximum scores for the shortest experiences.

Abstract
The purpose of this study was to measure the subject's sense of presence while they performed a task (riding a bicycle downhill) in a virtual reality (VR) environment and to compare it by body position (standing vs. sitting) and gender. The sample consisted of 35 subjects (19 male and 16 female) between 17 and 33 years of age. A translated and validated Portuguese version of the lgroup Presence Questionnaire (IPQp) and the Reflexive Motor Acts (RMAs), based on direct observation, were used as metrics. The results showed significant differences between body position at the level of Experienced Realism, Spatial Presence and Overall Sense of Presence. When measuring RMAs, it was demonstrated that people in the sitting position presented a higher frequency. We concluded that body position influences perceptions of credibility, which has an impact on the sense of presence. No differences were identified between the genders.