The study of the origin and evolution of consciousness presents several problems. The first problem concerns terminology. The word consciousness comes from the Latin term conscĭentĭa that means “knowledge shared with others.” However, the term consciousness also refers to several other aspects involving both its levels (sleep, coma, dreams and waking state) and contents (subjective, phenomenal and objective). A second issue is the problem of other minds, namely, the possibility to establish whether others have minds very like our own. Moreover, human consciousness has been linked to three different forms of memory: procedural/implicit, semantic and episodic. All these different aspects of consciousness will be discussed in the first part of the chapter. In the second part, we discuss different neuroscientific theories on consciousness and examine how research from developmental psychology, clinical neurology (epilepsy, coma, vegetative state and minimal state of consciousness), neuropsychology (blindsight, agnosia, neglect, split-brain and ocular rivalry), and comparative neuropsychophysiology contribute to the study of consciousness. Finally, in the last part of the chapter we discuss the distinctive features of human consciousness and in particular the ability to travel mentally through time, the phenomenon of joint intentionality, theory of mind and language.
