Instead of forcing subjects to become aware of their own awareness–in the process perturbing the very phenomenon one wishes to measure–wagering is a more implicit, a more indirect, way to assess awareness. And, an important practical concern, wagering is more natural, more intuitive, for subjects than introspection.
Most intriguingly, Persaud’s method implies that computing expected gains and choosing the more profitable outcome–that is, placing a bet–has a close and intimate connection to awareness…
That is from Nature Neuroscience, February 2007, gated. The article is "Betting the House on Consciousness," by Christof Koch and Kerstin Presuschoff. Another relevant piece from the same issue is "Post-decision wagering objectively measures awareness," by Navindra Persaud, Peter McLeod, and Alan Cowey.
Thanks to Neil H. for the pointer.