cautious vs observant

cautious

adj
  • Using or exercising caution; careful; tentative 

observant

adj
  • Diligently attentive in observing a law, custom, duty or principle; regardful; mindful. 

  • Alert and paying close attention; watchful. 

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