intrusive thought vs motivation

intrusive thought

noun
  • an unwelcome involuntary thought, image or idea 

motivation

noun
  • An incentive or reason for doing something. 

  • Something which motivates. 

  • A research rating that measures how the rational and emotional elements of a commercial affect consumer intention to consider, visit, or buy something. 

  • The action of motivating. 

  • Willingness of action especially in behavior. 

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