receptivity vs reciprocation

receptivity

noun
  • The state of being receptive. 

  • The extent to which something is receptive. 

reciprocation

noun
  • The act of reciprocating; interchange of acts; a mutual giving and returning 

  • Alternate recurrence or action; as, the reciprocation of the sea in the flow and ebb of tides; oscillation. 

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