intentive vs observant

intentive

adj
  • Paying attention; attentive, heedful. 

  • Expressing intent. 

  • Intent (of the mind, thoughts etc.). 

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 intentive and observant occurred in a corpus of books? (source: Google Ngram Viewer )