For thousands of years people thought we had 5 senses, now it's believed we have up to 33. In this ten-part series, philosopher Barry Smith and sound artist Nick Ryan take us on a journey into the extraordinary world of sensory perception.

In this episode: The brain has a more pro-active role in sensory perception than you might think. Rather than passively waiting for sensory input, like a blank slate waiting to be written on, the brain is constantly second-guessing what it expects from our senses.

Sometimes, it gets it wrong, and the world becomes a very confusing place.

Producer: Emily Knight. Show less