contemplation vs introspection

contemplation

noun
  • The act of contemplating; musing; being highly concentrated in thought 

  • The act of looking forward to a future event 

  • Holy meditation. 

  • The state of being considered or planned. 

introspection

noun
  • A looking inward; specifically, the act or process of self-examination, or inspection of one's own thoughts and feelings; the cognition which the mind has of its own acts and states 

How often have the words contemplation and introspection occurred in a corpus of books? (source: Google Ngram Viewer )