ambivalence vs doubtfulness

ambivalence

noun
  • A state of uncertainty or indecisiveness. 

  • The coexistence of opposing attitudes or feelings (such as love and hate) towards a person, object or idea. 

doubtfulness

noun
  • The state or quality of being doubtful; doubt; uncertainty. 

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