Feeling Present in Mixed Reality 7 for mediated presence to occur is that information is presented in a concrete form that an observer can make sense of intuitively (and literally, through sensations of the body), rather than having to think about. The result is the feeling of being in an external world, of presence. Referring back to the roots of the feeling of presence, Waterworth and Water- worth (2010) propose that when we experience strong mediated presence, we experiencethat the technologyhas become part of the self, and the mediated reality to which we are attending becomes an integrated part of the non-self, the world around the self. When this happens, in the same way as when we act directly in the physical world, there is no additional conscious effort of access to information presented in a medium, nor is there an extra effort of action to respond in the mediated environment.This is the ideal case of human-computerinteraction. FragmentedPresence in Mixed Reality As we have seen, and especially thanks to the proliferation of mobile devices and distributed systems, we often interact with both the physical world in which we are located and with the digital world of phone calls, text messages and chats, tweets, uploadedimagesandnewsfeeds.Someofthesewillevokepresenceinthemedium, to a greater or lesser extent dependingon the form in which theyare transmitted,but others will generate mental absence as we attend to them. In current mixed realities, a sense of presence in the physical world is often in competition with both presence andabsencein the virtual world of the digital. Cognitive load will tend to be inversely related to the level of presence experi- enced, since it is a reflection of the abstractness of a communicative medium. The locusofattention is anotherimportantfactor (Waterworthand Waterworth 2001).A concrete,perceptualpresentationofinformationwillinterferelesswithaothermore abstract task than an abstract description. While high cognitive loads will interfere more with other types of attention-demanding task than will low cognitive loads, twoperceptual(andthuspotentiallypresence-evoking)tasks may stronglyinterfere with each other even though each imposes a relatively low cognitive load. If the individual is already focusing his or her attention on the external world, as when driving, there will be a conflict between one perceptual task (driving) and another (say, looking at a navigation system display). In short, our sense of presence in current mixed realities is complex and fragmented. Another significant feature of digital communications is their frequent lack of symmetry. The different parties in an interaction will often be in different kinds of physical and/or digital situation, with very different characteristics. In two completely different situations the same message may be experienced in very different ways. At one end of a conversation, a person may be ready and able to be fully immersed in the communicative medium. At the other, the would-be communicatormayhaverestrictedattention,orbandwidth,or both,to devoteto the interaction. A relatively abstract form of communication may also be a matter of