What are the neurological differences between conscious processes and other cognitive processes? Think of the difference between when you report that what is in front of you is an image of a cross, and when a blindsighter reports the same thing. The blindsighter doesn’t experience anything in front of him or her and, through contrastive analysis, we will presumably find that you have an intact visual cortex but the blindsighter doesn’t. In Baars’s view, this would be contrastive evidence that the visual cortex is necessary for visual perception. Another piece of evidence is that if we directly stimulate the visual cortex, we can produce flashes of light. This doesn’t happen if we stimulate other parts of the cortex.
The study of binocular rivalry is a further example of contrastive analysis. Binocular rivalry occurs when one image is presented to the left eye and another is presented to the right. In a binocular rivalry experiment, one eye might be presented with a vertical dash and the other with a horizontal dash. You are simultaneously exposed to these dashes and nothing else. Interestingly, you will become conscious of only one of the dashes. They might alternate, but they don’t occur simultaneously. What is the difference between the train of rivalry processing that leads to a conscious experience of a dash and that which doesn’t? If we try to answer this question, we could learn something about the requirements for conscious visual experiences.
Contrastive analysis will allow us to build theories of consciousness, and that is all we need to explain consciousness. In the words of Baars:
Any theory that can account for this [contrastive] evidence deals with some aspect of consciousness. If we ever find a coherent explanation for all the contrastive evidence we will have a complete theory. (Baars 2007, p. 238)
Our initial theories might be rough, but with time, they will improve so much as to resolve the mystery of consciousness. Mapping out the cognitive systems of the brain that operate with essential connections to consciousness—and contrasting them with those that operate without—is an important part of the development of theories of consciousness.