First, watch this scene from Ex Machina...
The blonde character represents, I believe, the majority of the audience. When we think of consciousness, we think of intelligence. When we think of intelligence, we generally think of a sort of reasoning that is fast and extremely accurate. Therefore, consciousess -> intelligence -> extremely fast and accurate.
I've wondered occasionally just how conscious people really are. I don't mean metaphorically; I mean literally. Do all people have the same level of consciousness? If we use the definition from the prior paragraph as our rubric, then I think it would be obvious to say no because there's just a variation of intelligence from person to person. However, that's uncomfortable for many to think about, so we don't go there.
That's not what I'm getting at though. To me, Plato hit more closely on what consciousness is when he said, "an unexamined life is not worth living". Let's go with the idea that consciousness is continued examination.
We aren't robots though; we have many parts to our brain, many which conflict. Full consciousness, it would seem, is to tap into all areas of the brain. It's an examination of your surroundings, of your feelings, of your next strategic decision. Bridging these gaps is nebulous. What is an abstract concept in relation to the tree in your front yard in relation to heartbreak or love?
Let's try a different line of reasoning. Consciousness is what humans have (or at least we can start there until we can study and verify a new type of consciousness). Humans have an imperfect sort of web that ties together all kind of technically unrelated thoughts, from different domains of knowledge and different parts of the brain.
How would you code that? Sure, you can just call it a random process, and you have met the 'imperfect' criteria. Like the bearded guy from the video though, I don't think we can stop there. There's clearly something that is not completely random about people, otherwise we'd all be completely different. As much as we want to believe, we're not that different in many ways. What are the things that make us not different?
Is it purely natural that we are not different, or is it artifical because we simply influence each other? I think this nature vs nurture argument is irrelevant for two reasons:
There are many 'forces' upon a human psyche, some of them instinctual and some of them more relative to other people. Basic needs like eating and sleeping would induce some similar patterns of behavior among humans, as would the many cases where basic needs (or desires, which are infinite; see the economic problem) of two humans conflict. These forces will shape the person. As some like to say, we are often a product of our environment.
Read that last sentence again. 'We are a product of our environment'. If we are conscious, due to our imperfect but not entirely imprecise methods of reasoning, and we are a product of our environment, then are we not conscious because of environment? You might think I'm leaving the lower needs out of this equation, like eating or sleeping, but those psychological influences surely come from the environment too; we've envolved to want them because it helps us live.
There's a concept called cultural evolution. It's similar but slightly different from Richard Dawkins' meme theory (yes, memes existed before the internet) from his famous book in 1976. Dawkins' memes were tiny, atomic ideas that could be clearly defined and reproduced perfectly. Cultural evolution says that ideas are more complicated than that. However, as a whole, ideas can evolve just like life: through variation and selection.
There's a fun website that I discovered recently which will take you through the paces of a simple game theoretical thought experiment. I urge you to spend the time to read/do it all. It's much easier to intuit by demonstration than by tautological means. I think most would admit already that people will form belief systems based upon the environment that they are in, but this is a careless thought. That website explains how much more pervasive this force might be in shaping us as humans.
There's just one issue with the experiment from that website. Yet again, people are modeled as calcuating machines with simple logic for their decisions. If we were take it totally literally, we could arrive at the conclusion that individuals humans can't be conscious at all. Their arrival at any given idea is the product of random processes + repetition (which selects for certain ideas and then reproduces, making those people similar). At a very technical level, we could reduce things to this, in the same way we can say that everything in the universe is merely a consequence of quantum physics. However, it has no fidelity; it's a weak statement because it glosses over many layers of abstraction that can predict a lot more about the world.
What if we did say no individuals were truly conscious though, and only groups of humans attain consciousness? This is a slippery slope. How can a single species be conscious all on their own? What about the interactions between species? (As a sidenote: the taxonomy of speciies is an imperfect science; perfect boundaries between different life forms don't exist). You could just say that there is one world (or "universe" — sorry, aliens) consciousness.
I'm going to conclude with a couple things. After all, I am a human and a clear answer here would just be against my nature.