In 2008, neuroscientist Giulio Tononi at the University of Wisconsin-Madison's Center for Sleep and Consciousness put forward his "integrated information theory," which is currently accepted as one of the most compelling explanations about what consciousness is.

One of the central claims of the theory is that, for consciousness to exist, it must have "cause-effect" power on itself.

Neurologist Melanie Boly, a resident at UW's School of Medicine and Public Health who has worked with Tononi, explains that for anything to exist, it must be able to have an effect; it must be able to make some small difference to something else.

"Consciousness exists for itself and by itself," says Boly. "Thus it should have cause and effect on itself."