Surfing on a screen to get information and to access the online shopping market is now a usual activity. While this browsing activity has been the subject of numerous research, they focus primarily on an individual practice, while the user is supposedly navigating alone on the device. However, sharing a screen while surfing together has become a frequent activity, especially in stores where shop assistants are equipped with digital devices (computer, tablet, smartphone ...), also in order to navigate with their customers.This thesis aims at understanding the new practices of interaction around a screen between customers and shop assistants in the stores. Its purpose is to identify the motivations of customers to be or to agree to be with a shop assistant on the same screen. In addition, it analyzes the screen-sharing practices and the most appropriate conditions for such sharing. Due to the lack of theoretical research on this subject, this thesis draws up a review of literature inspired by other disciplines. Thus, she opts for a multidisciplinary literature review, particularly drawing on research about collaborative processes around a computer in learning and work situations.Adopting a positivist epistemological framework, this thesis implements a mixed methodological approach of qualitative (observations and interviews) and quantitative techniques (based on a quantified projective approach), in order to better understand the determinants and mechanisms of this phenomenon.Different results have been highlighted. First, it shows that there are different modes of screen-sharing and that different motivations can explain the desire to share it. In addition, it emphasizes the most compatible conditions for such screen-sharing activities. For example, the acceptance or the desire to share a screen with a shop assistant appears to depend on the customer's perception of the shop assistant, and of the level of relational, technical and digital competences he attributes to him. Similarly, the situation in which this sharing occurs (atmosphere, type of device used, and more…) could also affect the customer's appetence to share a screen. The amplification effect that the screen plays in the relationship between the shop assistant and his customer needs also to be notified. Finally, this thesis highlights how social exchange norms as well as the customer's perception of his own power determine the customer's choice of a specific screen-sharing mode with the shop assistant.Regarding the implications of this research, it provides a better understanding of what motivates customers to share a screen with shop assistants and the mechanisms behind such a sharing. It also provides a frame of reference to assist shop assistants in their decision about with whom, when and how he could initiate a screen-sharing journey, aimed at improving customers' satisfaction and experiences in the store. In the actual "phygital" era, it allows to understand the interest of using a screen during an exchange between customers and shop assistants.