4 1 Introduction: Divided Presence in Mixed Reality interaction possible. If we design for embodiment in the right way, the potential for sharedunderstandingshouldalsofollow,evenbetweenpeoplewhoexistindifferent contexts. The second characteristic that we will consider in the book also draws on our embodied nature. This is our evolved sense of presence, which makes it possible for us to carry out our intentions and act in the world in which we currently find ourselves– whetherthis is physical, digital, or a mixture of the two. Together, these two aspects form the basis for what we call human-experiential design.Before delving more deeply into these two aspects of our design approach, we highlight belowsomefeaturesoftheproblemsandopportunitiesthat HCI design faces. Throughtheever-increasingproliferationofcommunicationtechnologies,weall live in a variety of mixed realities formed from both the physical world and a virtual worldofdigitizedinformation.Wetakewithusmobilecommunicationdevices,and use them as we move through the physical world. While we are physically in one place, we are often mentally in another, or more than one other place, as we check e-mail or chat or chat with text or simply talk to other people in other places as we walk around, or eat or travel in vehicles. Increasingly, the devices that accompany us know where they are and can provide us with location relevant information, including the location of other people we may know. Increasingly, though still to a muchlesser extent, the physicalenvironmentswe movethrougharealso equipped withembeddedsensors,thatcandetectourpresence,andadaptivedisplays,thatcan provide us with contingent information that is more or less relevant to our needs at that time and place. This is the kind of mixed reality in which we all live. It is designed, but only in a piece-meal fashion. Parts of it are designed in detail, and some may be designed to work in combination, but overall the way the environment works and responds to us is not well adapted to supporting smooth transitions between the various functionalities of the many devices and systems we use and the different topographical and practical variations of the places in which we are physically located. In this way, our lives have become spread between two intertwined, but not yet integrated, realities: the physical and the digital. Social interaction is similarly split, we struggle to manage our encounters with distant others brought to us via technology while simultaneously trying to fulfill the social expectations of those in our current physical vicinity. We seek to be psychologically and socially present both in the physical and the virtual world of networked communications. But since presence is an attention-demanding state (as we discuss later in this chapter), and because these worlds are mixed but not integrated, this is a troublesome and sometimesevendangeroustask. Oursense ofpresenceis split betweenthe physical anddigital worlds we inhabit. Moment by momentwe must decide which reality to prioritize, and how and when to switch attention between the two becomes a major concern. Blended (rather than mixed) reality (and which has also been termed “inter- reality” and “integral reality” – see, for example, Gaggioli et al. 2011) has been proposedas the answer to the dilemma of split presence inherent in mixed realities.