what you see is not what you see

When I attended that talk about creativity as part of the World Science Festival several weeks ago, I arrived at the lecture theatre quite early (as I do). As I sat and waited for the talk to begin, I watched the slide show of random interesting facts that they had playing. One of these facts was about how we blink so often, that we spend about 10% of our time awake with our eyes closed.

Since then, I’ve thought intermittently about this – perhaps while sitting at a computer, thinking that we blink less while staring at screens of some sort; or perhaps while out and about in the world, and wondering about all the details that I’m missing by inadvertently having my eyes closed 10% of the time – but I always reasoned that it couldn’t be that significant a loss, since it’s not like we have our eyes closed for entire blocks at a time (say, for example, 6 minutes at the start of every hour) and then keep our eyes open the rest of the time. And because blinking takes next to no time at all, and it’s so spread out, we’re not really losing anything in our experience of the world, right?

In the last few weeks, I’ve also watched a couple of episodes of a documentary series called “Secrets of the Brain”, hosted by neuroscientist David Eagleman. I didn’t watch the first few episodes for reasons I can’t remember (probably late coming home from work or something), so I decided to get on the SBS website and watch the ones I missed.

The first episode (of season one? Didn’t even realise there were seasons) was about the concept of reality and our perception of reality. A big part of this involves our senses, and Eagleman talks a great deal about sight in particular. As it turns out, the processing of visual information is more complex than the processing of auditory information, or that of our other senses.

The basics of it, as I understand from the documentary, is that our eyes receive visual information from the outside world, and send signals to the thalamus, which is the “junction” of all sensory information (that’s why taste is influenced by smell), and the thalamus then relays this to the visual cortex of the brain. However, rather than being a straightforward pathway of your eyes receiving an image, and then your brain perceiving the image, there’s also information being sent from the visual cortex back to the thalamus, and this shapes the reality that we “see”.

In fact, the information being sent back from the visual cortex to the thalamus is about six times as much as what it’s receiving. Consequently, Eagleman argues, our perception of the world around us is influenced more by what we already know – our “internal model” of the world – than by what we’re actually seeing. This internal model begins construction from the moment we are born into the world, and is built upon a foundation of information from all of our senses. When we’re older, and this model has been more or less established, what our eyes are seeing (the information relayed from the thalamus to the visual cortex) just contributes to refining and correcting this version of reality.

A good example Eagleman uses in the documentary is a plain, white, hollow mask of Einstein’s face (it’s not really important that it’s his face, but it just happened to be so). The mask is mounted on a small pedestal, and rotates slowly. Although it is obvious that there is one concave side and one convex side, as the mask rotates, the concave side has the illusion of appearing to be convex. Eagleman explains that this is because we’re used to seeing faces that come outward (essentially convex) rather than inward (concave), so this is our visual cortex telling our thalamus that the mask must be convex.

Something else I found rather fascinating was the story of a man called Mike, who lost his sight when he was three years old, as a result of a chemical explosion. Years later (when he was 40?), his sight was restored using stem cells. However, because he hadn’t been able to see for most of his life, when his sight was finally restored, his brain didn’t know what to do with all of this new visual information that his eyes were taking in. He had problems with depth perception and distinguishing objects; he had difficulty with facial recognition and learning to read words; and he still requires a guide dog even though his vision is now fine. So, really, it’s not as simple as just seeing and then knowing.

And even when we do see and think that we understand, we still miss a lot of details – maybe because our brains decide those details are unimportant or because our brains are already filling in the blanks with its own version of reality. It’s the same argument about people not really paying attention even though they think they are, and the same problem confronted with suspect lineups and witness statements.

And so, going back to my original pondering about the loss or otherwise resulting from having our eyes closed 10% of the time that we’re awake, I suppose it really isn’t such a big deal after all. I mean, it doesn’t sound like having our eyes open more of the time would actually help us get much more out of the world, especially considering that we ignore a lot of details, and the brain just keeps reconciling new input with past experiences.

(If you have an interest in how the brain works and the concept of reality, I highly recommend the “Secrets of the Brain” documentary series.)

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