cognizant vs observant

cognizant

adj
  • Aware; fully informed; having understanding of a fact. 

  • Sapient; self-aware. 

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