In their book A Universe of Consciousness, Edelman and Tononi use the example of a photodiode discriminating light to illustrate the problem of consciousness:
Consider a simple physical device, such as a photodiode, that can differentiate between light and dark and provide an audible output. Let us then consider a conscious human being performing the same task and then giving a verbal report. The problem of consciousness can now be posed in elementary terms: Why should the simple differentiation between light and dark performed by the human being be associated with and, indeed, require conscious experience, while that performed by the photodiode presumably does not? (p. 17)
Does discrimination of a stimulus from a background “require conscious experience”? I don’t see why it would. This seems like something the unconscious mind could do all on its own and indeed is doing all the time. But it comes down to how we are defining “consciousness”. If we are talking about consciousness as subjective experience, the question is: does discrimination require there be something-it-is-like for the brain to perform that discrimination? Perhaps. But I also don’t know how to answer that question empirically given the subjective nature of experience and the sheer difficulty of building an objective consciousness-meter.
On the other hand, assume by “consciousness” we mean something like System II style cognition i.e. slow, deliberate, conscious, introspective thinking. On this view of consciousness, consciousness is but the tip of the iceberg when it comes to cognitive processing so it would be absurd to say that the 99% unconscious mind is incapable of doing discrimination. This is the lesson of Oswald Külpe and the Würzburg school of imageless thought. They asked trained introspectors from the Wundtian tradition to make a discrimination between two weights with their hands, to see if one weight is heavier than the other. Then the subjects were asked to introspect and see if they were aware of the process of discrimination. To their surprise, there were no conscious images associated with the weight-discrimination. They simply held the weights in their hand, consciously made an intention to discriminate, the discrimination happened unconsciously, and then they were aware of the results of the unconscious judgment. Hence, Külpe and the Würzburg school discovered a whole class of “imageless thought” i.e. thought that happens beneath the level of conscious awareness.
Of course, the Würzburg school wasn’t talking about consciousness in terms of subjective qualia. They were talking about consciousness in terms of what’s introspectable. If you can’t introspect a thought process in your mind then it’s unconscious. On this view and in conjunction with evolutionary models of introspection it seems clear that a great deal of discriminations are happening beneath the surface of conscious awareness. This is how I prefer to talk about consciousness: in terms of System II-style introspection where consciousness is but the tip of a great cognitive iceberg. On Edelman and Tononi’s view, consciousness occurs anytime there is information integration. On my view information integration can occur unconsciously and indeed most if not all non-human animal life is unconscious. Human style slow deliberate introspective conscious reflection is rare in the animal kingdom even if during the normal human waking life it is constantly running, overlapping and integrating with the iceberg of unconsciousness so as to give an illusion of cognitive unity. It seems as if consciousness is everywhere all the time and that there is very little unconscious activity. But as Julian Jaynes once said, we cannot be conscious of what we are not conscious of, and so consciousness seems pervasive in our mental life when in fact it is not.