mindful vs observant

mindful

adj
  • Being aware (of something); attentive, heedful. 

noun
  • As much as can be held in one's mind at a time. 

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