Abstract
In recent years there has been a boom of different natural interaction paradigms, such as touch, tangible or gesture-based interfaces, that make better use of human's innate skills rather than imposing new learning processes. However, no work has been reported that systematically evaluates how these interfaces influence users' performance with regard to their level of digital literacy or even age. Furthermore, it is also important to understand the interaction paradigms' impact when performing basic operations, such as data selection, insertion and manipulation, and which interface could be the most efficient for each task. This paper reports the first step of an exploratory evaluation about the relationship between different interaction paradigms and specific target-audiences: dealing with a selection task. We conducted an experiment with 60 subjects to evaluate how different interfaces may influence the performance of specific groups of users. Four input modalities are evaluated in a selection task and results for these different user groups are reported in terms of performance, efficacy (error rate) and user preference. For each group of users, we determined there was a statistically significant difference between the mean time taken to complete the task in each interface. Also, the one input modality every user was accustomed with (the computer mouse) was the one that showed the most discrepancy regarding performance between the groups. We believe that this study raises new issues for future research. Copyright 2014 ACM.

Abstract
This paper presents a study on the evolution of digital skills of a group of people with intellectual disabilities, when performing tasks such as painting, making puzzles, playing games, or word search. For the effect, we compare results in two assessment moments: in the first one, the group with intellectual disabilities had little or no experience as regards as performing universal tasks (selection, manipulation and navigation) and with the Web; in the second one, the group had some experience obtained within the 6 months after the first assessment moment. We aimed at evaluating the evolution of their digital skills by comparing the two assessment moments through the following usability variables: successful conclusion of activities, type of difficulties found, errors, satisfaction, motivation and autonomy indicators. The results revealed that participants showed learning skills when performing all the three universal tasks (namely: selection, manipulation and navigation) which is indicated by the number of participants that was able to conclude the activities, also confirmed by the prominent results of the second assessment moment. When it comes to errors, they made more errors in the first assessment moment, in general. When handling the input devices the participants had a better performance with the mouse than the keyboard. On the other hand, they improved their keyboard handling. However, it was observed that it is not a device that they can be autonomous with due to their reading/writing difficulties, which itself represents a didactic challenge when it comes to the very presentation of appropriate methodologies and techniques that may help them overcome such problem.

Abstract
Visual coherence between virtual and real objects is a major issue in creating convincing augmented reality (AR) applications. To achieve this seamless integration, actual light conditions must be determined in real time to ensure that virtual objects are correctly illuminated and cast consistent shadows. In this paper, we propose a novel method to estimate daylight illumination and use this information in outdoor AR applications to render virtual objects with coherent shadows. The illumination parameters are acquired in real time from context-aware live sensor data. The method works under unprepared natural conditions. We also present a novel and rapid implementation of a state-of-the-art skylight model, from which the illumination parameters are derived. The Sun's position is calculated based on the user location and time of day, with the relative rotational differences estimated from a gyroscope, compass and accelerometer. The results illustrated that our method can generate visually credible AR scenes with consistent shadows rendered from recovered illumination.

Abstract
Navigation in virtual environments is important because it allows the exploration of the virtual worlds. This paper presents an objective performance evaluation (based on the Steering Law) of two types of navigation: natural (real walking) vs. not natural (gamepad). Steering Law was the objective performance metric chosen since it captures the relationship between the time to travel a path and the difficulty of that path. In addition to the performance, subjective metrics were also considered, namely the feeling of presence, cybersickness and user satisfaction. The participants had to complete a series of paths with different difficulty indices and the time that a participant took to go through each one was measured. Overall results show that navigation through real walking had better performance, presence, cybersickness, and satisfaction than the gamepad interface.

Abstract
Virtual Reality offers the possibility of creating the most diverse types of videogames, being possible to have different types of videogames such as calm, eventful or even terrifying. The present study aimed to verify whether different types of videogames have impact on player's emotional responses as wecc as on the self-reported sense of presence. In addition, two distinct display interfaces were considered: conventional computer display and head-mounted display. To carry out this study, an experimental study was designed based on three videogames with distinct natures (exploration, puzzle and horror), where the participants had to fulfill certain tasks within a predetermined period. The data analysis revealed that there no significant emotional changes between the different videogames used. The results also revealed that the use of head-mounted displays increases the sense of presence in scenarios where the field of view is wide.

Abstract
Novel input modalities such as touch, tangibles or gestures try to exploit human's innate skills rather than imposing new learning processes. However, despite the recent boom of different natural interaction paradigms, it hasn't been systematically evaluated how these interfaces influence a user's performance or whether each interface could be more or less appropriate when it comes to: 1) different age groups; and 2) different basic operations, as data selection, insertion or manipulation. This work presents the first step of an exploratory evaluation about whether or not the users' performance is indeed influenced by the different interfaces. The key point is to understand how different interaction paradigms affect specific target-audiences (children, adults and older adults) when dealing with a selection task. 60 participants took part in this study to assess how different interfaces may influence the interaction of specific groups of users with regard to their age. Four input modalities were used to perform a selection task and the methodology was based on usability testing (speed, accuracy and user preference). The study suggests a statistically significant difference between mean selection times for each group of users, and also raises new issues regarding the "old" mouse input versus the "new" input modalities.