altruism vs self-interest

altruism

noun
  • Action or behaviour that benefits another or others at some cost to the performer. 

  • Regard for others, both natural and moral without regard for oneself; devotion to the interests of others; brotherly kindness. 

self-interest

noun
  • One's personal interest or advantage, especially when pursued without regard for others. 

How often have the words altruism and self-interest occurred in a corpus of books? (source: Google Ngram Viewer )