Should fantasy distractors be avoided in multiple choice questions Is there any reason not to include fantasy distractors (made-up wrong answers) in multiple choice tests. 

Examples: 
What is the name of the compound HCl?

a) Hydrochloric acid

b) Chlorohydride acid

c) Chlorohydric acid
etc 

What is the term for a parasite that cannot complete its life cycle without its host? 

a) Obligate parasite (correct)

b) Parasitic obligate (fantasy word)

c) Mandatory parasite (fantasy combination)

Fantasy distractor definition: Usually one chooses distractors that a student could confuse with the correct answer, based on knowledge of common cognitive models of the field. I call a fantasy distractor a distractor that is a made-up word - typically it would be used for testing/learning complex terms that consist of a combination of etymological roots by rearranging them or mixing them up.

Potential concerns: How high is the risk that students remember the fantasy distractor? What is the best practice on  such fantasy items? 

Rationale for having fantasy items: The reason for asking is that it seems having a greater number of distractors can make the test more of a retrieval test than a recognition test. Getting plausible non-fantasy distractors (eg in chemistry can be tough).
I would say no, there's no reason not to, and in fact it might be better, based on the following rather speculative reasoning.

In general, despite the general benefits of testing for learning, multiple choice testing can also lead to subsequent memory for incorrect responses, i.e. it can cause students to learn false responses.


  Marsh, Roediger, Bjork, &amp; Bjork (2007) "The memorial consequences of multiple-choice 
  testing." Psychonomic Bulletin &amp; Review, 14(2) 194-199


This doesn't explicitly compare fantasy answers to other misleading answers, but intuitively, it seems that such "false learning" would be MORE likely to be reinforced in the future for plausible responses than for fantasy responses.  The reason is that fantasy responses are unlikely to ever be encountered again, while plausible responses might be, leading to reinforcement of the false learning.

See also here regarding avoidance of false learning from multiple choice testing:


  Little and Bjork (2012) "The persisting benefits of using multiple-choice tests as
  learning." Proceedings of the 34th Annual Conference of the Cognitive Science Society.