## 1 Introduction
VR also offers the possibility to test the patient's progress within controlled, ecological, and secure testing environments, that reproduce the crucial characteristics of the real world and are selected ad-hoc for each patient and situation (e.g., [16; 17]). In experimental settings, VR systems allow researchers to design dynamic and realistic environments (virtual environments or VE), while monitoring behavioral and physiological responses [18]. The high degree of control allowed during the investigation of the cognitive and behavioral components of a certain skill is an additional advantage. It has been demonstrated [19] that the patients are able to transfer what they have learned from VE to real life. Spatial navigation skills have been the object of several studies involving VR (e.g., [20; 21]. The results of such studies suggest that the mental representations of space in VE resemble those implicated in the navigation of the real world. [PERSON] and colleagues' systematic review [14] has shown improvements in spatial memory after practicing with navigational tasks in VR. Most importantly, it has shown a transfer of the improvements to more general aspects of spatial cognition. Both immersive and non-immersive VR systems have been shown to improve navigation and orientation abilities. It has even been proposed that the improvement observed in visual-constructive abilities, attention and upper limb metricity could be due to the so-called shadow effect (i.e., the patient's shadow on the screen while performing VR training) of the immersive system [22]. At the neurophysiological level, the mechanisms through which VR works are only partially understood. It is hypothesized that VR entrains the same neural pathways that are involved in motor learning and motion-related cognitive processes [23]. VR training thus seems to promote brain plasticity through mechanisms related to the reactivation of brain neurotransmitters, and its results can be even better than those obtained by conventional treatment [24; 25]. As to the applications of VR with children, most have addressed motor problems [26], for instance in cerebral palsy [27; 28], or cognitive, social and emotional problems, especially in autism spectrum disorders [29; 30; 31]. However, VR applications are not restricted to neurorehabilitation and more and more experiences involving its use are found also in educational contexts [32]. The general psycho-educational framework is that of neuroconstructivism, where cognitive development occurs through the pro-activity of the child in exploring, manipulating, and interacting with his/her environment [33]. According to the theory of social constructivism [34], moreover, the learning environment should encourage the pupils to collaborate and participate actively, experiment, share and develop ideas, use language to reason, plan and reflect on one's actions. In [PERSON] et al. [35], it has been suggested that immersive virtual reality technology provides an alternative educational process by providing a knowledge-building experience. It is crucial that learning goals and solutions are established in collaboration with teachers [36]. The authors underscore that individual factors like age, gender, computer experience, psychological factors, cognitive and learning styles are likely to strongly affect learning outcomes, as well as technology-related factors such as immersivity, so that empirical studies are needed to determine which characteristics of virtual environments can really be pedagogically exploited. Less recent, but seminal studies, such as [PERSON]'s [37], suggest that among the main features contributing to learning, there are free navigation and first-person point of view, the manipulation of the relative size of objects in virtual worlds, the transduction of otherwise imperceptible sources of information, and the reification of abstract ideas.