The present thesis sought to elucidate the possible underlying mechanisms to a striking phenomenon of sensing someone you cannot otherwise perceive, but you can nevertheless recognize varying degrees of its identity traits. I explored its phenomenology in the clinical context, probing iPH utility as a potential marker of Parkinson's disease progression and aimed to design quantification methods usable in clinical contexts, such as the novel HEIDI scale (Hallucination-evoked IDentity Index), proposed here. Exploring the differences in patients clinical state and neural network variability, the Limbic, Somatomotor and Default Mode Network regions might indicate self-related processing involvement, as well as potential activation of person recognition pathways. Turning to induced PH, I found a perceptual bias for the partner's identity reflecting findings from spontaneous presences commonly described as those of close others. Additionally, such iPH extends beyond the sensing of personally familiar individuals and can also be perceived as supernatural agents. Taken together, I present the possibility of iPH being derived from fundamental social perceptual and cognitive biases such as hyper-detection of social agents, to specific facilitation and advantageous processing of highly familiar conspecifics (like one's kin or in-group members). While these general social mechanisms are thought to confer evolutionary benefit for survival, they can also result in aberrant activations of those same over-represented identities following a disturbance in self-monitoring of somatomotor signals. While further work will have to elucidate the neural mechanisms involved in more detail and arbitrate between the proposed theoretical accounts for iPH emergence, a key idea has been illustrated: presences of identified Others are significant and impactful experiences across many different contexts and thus merit rigorous scientific efforts in its exploration. Taking the full breadth of their varieties into account, future work should be informed from research on fundamentally social mechanisms of our brain, as its likely primary mover.