appreciation vs mental grasp

appreciation

noun
  • A rise in value. 

  • The act of appreciating. 

  • A fair valuation or estimate of merit, worth, weight, etc.; recognition of excellence; gratitude and esteem. 

  • Accurate perception; true estimation. 

mental grasp

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