extroversion vs introversion

extroversion

noun
  • A personality orientation towards others and things outside oneself; behavior expressing such orientation. 

  • The condition of being inside out, especially in relation to the bladder. 

introversion

noun
  • A personality orientation towards the self and mental abstraction; behavior expressing such orientation. 

  • Arrangement of two similar words, lines, etc. to form the middle part of a structure. 

  • The action of turning one's thoughts upon internal or spiritual matters. 

  • A turning inward 

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