Consciousness is defined as the ability to experience things subjectively. There are active paradigms to detect it in non-communicating subjects (playing tenni

Consciousness is defined as the ability to experience things subjectively. There are active paradigms to detect it in non-communicating subjects (playing tennis in one's head while in an FMRI, for example), and research is under way to find passive paradigms. See for example: Preserved feedforward but impaired top-down processes in the vegetative state. http://www.ncbi.nlm.nih.gov/pubmed/21566197 http://www.ncbi.nlm.nih.gov/pubmed/21566197 , or this: http://blogs.nature.com/news/2012/10/a-tool-to-quantify-consciousness.html http://blogs.nature.com/news/2012/10/a-tool-to-quantify-cons...