I was cycling to my yoga class this morning. I have to cross a busy road with traffic lights and the thought shot through my mind that a green traffic light to a motorist is like a red rag to a bull – a sign to charge. Then I remembered reading somewhere that bulls are in fact partially colour-blind. They don’t see red. So the whole ‘red rag’ thing is actually meaningless. But you still hear people say, ‘It’s like a red rag to a bull.’
Then I wondered: if a person who’s colour-blind gets angry, do they still see red? I found an interesting site on this subject where scientific experiments showed that the perception of the colour red is actually related to the emotion of anger. Link in the first comment.
However these examples are not the same as dead metaphors. There are lots of metaphors, similes and other turns of phrase that are still ingrained in our language even though they are no longer relevant. Either because the objects mentioned are barely known nowadays – as black as coal, for example. A whole generation will probably never have seen coal. Or ‘I dialled the wrong number’ when it’s been many years since you could dial a number. Or because the original turn of phrase was actually quite discriminatory.
Let’s hear your examples!