I think there are three levels of symbolism in art. There is the personal symbolism that is only really known to yourself. It may be in your dreams; your ways of understanding things. If you are an artist it may be what you express. There is a universal symbolism, that anyone in any time can understand and interpret. That would probably be to do with core words, or facial expressions, for example. Then there is cultural symbolism that most within that culture can understand the meaning, but those outside in place or time, may not.