Illusions are a great way of getting us to think about how we are just biological creatures with biological systems at our disposal. No matter how weird and fantastic we think our brains are, the reality is that they are so much weirder and more fantastic. To paraphrase a famous astro-physicist (I think Neil deGrasse Tyson said the original quote): Our behaviour is not only weirder than we think, it is weirder than we can think! Take a look at two of my favourite (and very simple) optical illusions, which demonstrate in different ways how our brains process information about the world. The first is about how we process objects and the second is about how we process faces.

Lord of the Rings?

The first illusion is a very simple, but classic illusion involving concentric rings, which demonstrates quite nicely that the reality that we create in our minds about objects in space is simply an illusion created in our brains. Our brains have remarkable innate cognitive systems designed to re-create a 3-dimensional understanding of objects in space from a 2-dimensional image generated by the eyes.

Masked reality

The second optical illusion is the facial recognition test: can you tell which way the face is facing? There are two salient points to take from this illusion. The first point to note is that we have the ability to recognize faces from very simple masks, meaning that we must have some kind of inbuilt facial detection system in our brains. The second point is that our system works to detect faces even when we consciously know they are not there (as when we learn that the mask is the “wrong way round”, but we still see the face). Richard Feynman once said that Mother Nature cannot be fooled. But, here we see that our own natures can be!