In 1963, in a bid to settle a conflict with his English teacher, a 16yo student from San Diego sent a 4-question survey to 150 well-known authors of commercial, literary and science fiction.
"Did they consciously plant symbols in their work?" he asked.
Here are many of their wonderful answers, very much worth the read
https://www.theparisreview.org/blog/2011/12/05/document-the-symbolism-survey/