I have been banging on about how our brain constructs our reality in my books, lectures and most recently the Royal Institution Christmas Lectures (which are now permanently up on the Ri Channel). This reality even includes our sense of self – book out in a couple of months! The examples I usually give come from Gaetano Kanizsa’s seminal work with subjective contours. Not only do you see illusory shapes but you can record from brain regions that register these illusions as if they are really there.
Recently, a group of vision scientists demonstrated that individuals who were told that there were faces present in half of 10,000 random dot images believed that they detected them. Not really that surprising because we tend to believe what people (especially scientists in white coats) tell us. For me the interesting finding was differential brain activity on trials when they thought there was a face present.
Differential brain activity is a bit of a methodological nightmare as the past decades of brain imaging research has proven. What does that activity mean? There are a number of real problems unpicking what this activity reflects. I don’t think imaging by itself is going to convince critics. But here is one demonstration that I learned about this week that blew my mind for elegance. Take a look at these images.
This is beautiful brightness illusion. The centre of the pattern on the left looks much brighter – but it isn’t – it’s an illusion. But here’s the kicker. If you measure pupil size of the viewer, there is significant decrease in pupil size. This is normal response to brightness and has always been considered a basic low level reflex to calibrate for the amount of light entering the eye. Clearly, an illusion produces a change in the brain and its activity from the top-down all the way to lower level mechanisms.
The British philosopher Julian Baggini recently presented a great TED talk on the self “Is there a real you?” which I highly recommend. It is aimed at a young audience but none the less makes some critically important points. However, I think that he has misrepresented my position (and Susan Blackmore’s) when I say that the self is an illusion. That’s because I don’t think that Baggini (and many other smart people) understand my use of the term “illusion.” An illusion is not what it seems and I make this point explicit every time I talk about the mind.
The experience of self is very real, just like illusions, and this sense may even produce changes that are measurable. But consider the reality of ghosts. If we think we see a ghost, then to all intents and purposes, effectively we have. That does not make ghosts real. In the same way, if we think we have a self, and indeed measure activity of the self, that also does not make it real. Just like the Matrix, you do not have any direct contact with reality.