“But I thought you were blue!” That’s what Jake Sully, the main character in Avatar, says when he wakes up as an alien at the very end of the movie. Actually, the movie ends just before he has a chance to say anything, but that’s my guess about what he would have said. The question is: Why would he say that? (Or, if you’re a stickler: Why would I say he would say that?)
For those who haven’t seen the film, what you need to know is that Sully is a human who, from the safety of his brain-interface chamber back at the lab, can remotely control a “soul”-less alien body. And, at the end of the movie, and through the miracle of human suspension of disbelief, his human self gets literally uploaded into the alien’s body. Sully thereby becomes a bonafide eight foot tall, blue alien, and in the final frame of the movie we see his alien eyes open.
Question is: What does Sully see when he opens his eyes? And, more to the point: Does his new alien wife still appear blue to him?
By way of answering, let’s back up and remember what visual systems are for. When we look out at our world through our eyes, we implicitly believe we are seeing it as it truly is. Our eyes and visual systems are to us objective scientific measuring devices. But evolution does not select for objective scientific equipment – evolution selects for visual systems that best serve the animal and its reproduction. Although often the best perception is one that veridically reflects the truth, sometimes the best solution is a “useful fiction,” a little-white-lie perception that serves us better than an accurate accounting of the actual.
Consider the accent of your own voice. To you, you have no accent. It is other people that have an accent. And they think it is you that have an accent. Perceived accent, or “accentness”, is not a quality of the speech stream itself. Accentness is not an objective perception of anything out there. It depends on the baseline accent one has become adapted to, namely your own. When one adapts to a stimulus and it becomes baseline, the “qualitative feel” of that stimulus diminishes, i.e., it begins to feel like nothing to perceive it. The benefit of this is that even very tiny deviations away from the baseline feel perceptually highly salient. Your own accent doesn’t sound accented because it is your baseline accent, allowing you to be trigger sensitive to the modulations around it from the voices of different people and their different emotional inflections. This is also why you don’t notice any smell to your own nose, any taste to your own tongue, or any temperature to your own skin.
And, in addition, it is why you don’t perceive your own skin to be colorey. People perceive the color of their own skin (or that of the most common one in their experience) as uncolorey and difficult to name. This perceptual adaptation to the baseline skin color allows people to be highly sensitive to the subtle color modulations happening on the skin of others as a function of mood or state.
Now we can circle back to our earlier question. When Sully opens his eyes as an alien, does his alien wife still appear blue to him? And the answer is no. He’s one of them now, and will perceive his wife’s skin, and his own skin, as peculiarly uncolorey, no longer blue at all. He will also not notice the taste of his own alien saliva, something you can be sure he would have noticed were he to have tasted alien saliva as a human. And now we see why alien Sully exlaimed, “But I thought you wereblue!” Let’s just hope he wasn’t into her only because she was blue!
This first appeared on January 6, 2010, as a feature at the Telegraph.