act on vs modify

act on

verb
  • To affect something. 

  • To act decisively on the basis of information received or deduced. 

  • Το act accordingly to a (usually sublimated) desire or impulse. 

  • To take action against something. 

modify

verb
  • To change part of. 

  • To set bounds to; to moderate. 

  • To qualify the meaning of. 

  • To be or become modified. 

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