Synæsthesia is cross-over effect between different sensory modalities. The senses become mixed. A synæsthete might 'see' sounds or 'hear' colours, or days of the week might evoke personalities. True synæsthesia has a neurological basis and is involuntary. A 'feeling for the synæsthetic' is something every actor should develop, as it is his job to explore cross-modal metaphors in order to increase the richness and breadth of his expression.
Novelist A. S. Bryant (Possession) says that she sees her novels in patches of colours. Nabokov and 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