I am convinced that if given the choice, people will choose to do a multiple choice question over a fill-in-the-blank/short answer question which asks the same thing.  Reasoning could be explained that they have a better chance of getting the answer correct by having the correct answer in front of them (most of which having a 1 in 4 chance of picking the correct answer).  However, people tend to forget that many teachers (especially math) can give partial credit if work is shown  with a short answer question, particularly if some conceptual knowledge is displayed.  This cannot be done with multiple choice questions.

Many standardized tests can use this theory to their advantage, and can in turn become tricky with their multiple choice options.  In my opinion, the authors of the Integrated Algebra Regents exam are most comparable to the New England Patriots – they seek out your weaknesses and then drill them all day long.  The authors of the Integrated Algebra Regents know what students have difficulty with, and what mistakes are commonly made.  They will work out the problem using these common mistakes and make that an answer choice, causing the majority of students that make that common mistake to pick the wrong answer.  A good student will not make those mistakes in the first place.   A great student will recognize these tricks and use the process of elimination to help them ensure they have the correct answer, or at least a better chance of getting the right answer.

The Regents exams (math, at least) are complex exams.  They not only focus on the content being tested, but on how well a student performs on tests.  With the complexity of these exams, and the stress of performance effecting teacher evaluations, how can we blame teachers for teaching to the test?  Yes, ideally, if content is focused on, the students should be able to demonstrate their mastery by content knowledge alone.  However, if no instruction or preparation is given to show the students the nature of these tests beforehand, even the most competent student could fall into the trap of making common mistakes and choosing the wrong answer.