extinction vs strengthening

extinction

noun
  • The absorption or scattering of electromagnetic radiation emitted by astronomical objects by intervening dust and gas before it reaches the observer. 

  • The action of making or becoming extinct; annihilation. 

  • The inability to perceive multiple stimuli simultaneously. 

  • The fading of a conditioned response over time if it is not reinforced. 

strengthening

noun
  • The process by which something is strengthened. 

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