For those of you unfamiliar with the BBC documentary series
Horizon, they have produced a large number of excellent, rational, science-based documentaries over the decades.
Here's their home page.I just watched their documentary
Derek Tastes of Earwax which is about the condition of
synaesthesia: this is where parts of the brain that process different senses become inexplicably linked. For example: there are people who literally see colours when they read letters; there are people who experience taste when they hear a word (hence the title of the documentary). While this condition was once categorised as woo-woo nonsense along with seances and spoon-bending, it is now being treated with proper scientific research and experimentation. The results of these experiments imply that these cross-sensory connections are a part of us all to a degree and may have played a part in the development of language.
I highly recommend that anyone interested in how the human brain functions watches this documentary. Unfortunately, it didn't play on cable here in Canada. We had to download it.
Program summary.The official transcript, but it doesn't do it justice.