What is the difference between "target" and "foil" in experimental design? What is the difference between 


  "target"


and 


  "foil"


in experimental design in psychology?  And how is a foil different from a distractor?
A target is:


  A stimulus that a research participant or subject is searching for or
  trying to concentrate on, and that in research is often accompanied by
  distractors.


And a foil is:


  In research methodology, another name for a distractor.


For example, in a multiple choice question, the correct answer is the "target", and the rest are "foils" or distractors.  This is similar to a police lineup, where the suspect is the "target", and the rest are "foils" or fillers.  "Foil" and "distractor" are synonyms.