alertness vs incubation

alertness

noun
  • The quality of being alert or on the alert 

incubation

noun
  • Sitting on eggs for the purpose of hatching young; a brooding on, or keeping warm, to develop the life within, by any process. 

  • The development of a disease from its causes, or the period of such development. 

  • A period of little reaction which is followed by more rapid reaction. 

  • One of the four proposed stages of creativity (preparation, incubation, illumination, and verification): the unconscious recombination of thought elements that were stimulated through conscious work at one point in time, resulting in novel ideas at a later point. 

  • Sleeping in a temple or other holy place in order to have oracular dreams or to receive healing. 

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