From a Cartesian viewpoint perception comes first, which is in a large part determined unconsciously by our social conditioning. Our nature and our conditioning then lead us to verbal expression. Nature has a large role in determining the direction of the thought. However, the range of expression with language depends on our conditioning and education.
You can get too mechanistic or materialistic in describing how we produce language as well. For instance, in unusual circumstances when there are people who "speak in tongues" is there any thought process at all, or is it coming from another source beyond thought? In inspired speakers, is there what we would call conventional thought occurring in the background while they are speaking?