reflection vs thoughtlessness

reflection

noun
  • The act of reflecting or the state of being reflected. 

  • The process or mechanism of determining the capabilities of an object at run-time. 

  • The folding of a part; a fold. 

  • Something, such as an image, that is reflected. 

  • The property of a propagated wave being thrown back from a surface (such as a mirror). 

  • Careful thought or consideration. 

  • An implied criticism. 

thoughtlessness

noun
  • heedless disregard for the consequences of one's actions 

  • disregard for other's feelings 

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