Synaesthesia is a cross-over effect between different sensory modalities. The senses become mixed. A synaesthete might 'see' sounds or 'hear' colours, or days of the week might evoke personalities. True synaesthesia has a neurological basis and is involuntary. A 'feeling for the synaesthetic' is something all actors should develop, as it is their job to explore cross-modal metaphors in order to increase the richness and breadth of their expression.
Novelist A. S. Bryant (Possession) says that she sees her novels in patches of colours. Vladimir Nabokov and Olivier Messaien also experienced synæsthesia.
"La parole est une danse pour les oreilles et le geste est une musique pour les yeux. (Speech is a dance for the ears and gesture is a music for the eyes)"
- Jean-Louis Barrault