detect vs discern

detect

verb
  • To discover or find by careful search, examination, or probing. 

  • To work or solve cases as a detective. 

discern

verb
  • To detect with the senses, especially with the eyes. 

  • To distinguish something as being different from something else; to differentiate. 

  • To perceive, recognize, or comprehend with the mind; to descry. 

  • To perceive differences. 

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