Pareidolia is a psychological phenomenon that causes people to see patterns in a random stimulus. This often leads people to assigning human characteristics to objects. Usually this is simplified to people seeing faces in objects where there isn’t one. – fairly common – recognized as perfectly healthy tendency. (Wikipedia)
Maybe we should question this definition since we see them because they are there! Some artist purposefully hide symbols within their art in order to engage at a more subconscious level with people. Do you see faces and images where they are not expected? I know I do.