When we read the theories of consciousness, they usually state that a thing either has consciousness or does not have consciousness. Is there a reason why consciousness cannot be thought to be a spectrum? For example, I have more consciousness than a computer. (Implying that a computer has consciousness, just that it has less than I do.) Rather than I have consciousness, a computer does not.
On/off is indeed not the commonest view of consciousness. In Hindu philosophical circles, consciousness is thought of as continuous across living systems. Humans have 'budding'consciousness, (plus free will), animals 'shuttered' and plants 'covered'consciousness, and these are points along a continuum. (Reference example: Hinduism and Science, by T D Singh; a paper in “Science and Religion: Global Perspectives”, June 4-8, 2005, in Philadelphia, PA, USA, a program of the Metanexus Institute).