Understanding USMLE Distractors

To deal most effectively with exam questions, you need to have some understanding of how the questions are constructed. Getting a question correct means selecting the best answer. Incorrect options are called "distracters." Their purpose is to distract, that is, to get you to pick them rather than the best answer. Each distracter will be selected by some examinees, or it would not be included as an option. Every option fools somebody. Your job is to not be misled.

In general, distracters will seem plausible and none of them will stand out as obviously incorrect. Distracters may be partially right answers, but not the best answer. Common misconceptions, incomplete knowledge, and faulty reasoning will lead you to select a distracter. The NBME tells its question writers that their distracters must follow these five rules:

1. They will be homogeneous. For example, they will be all laboratory tests, or all therapies, not a mix of the two.

2. They will be incorrect or definitely inferior to the correct answer. There will be enough of a difference between the right answer and the distracters to allow a distinction. For example, if estimating the percentage of a population with a disease, the options will differ by more than 5%.

3. They will not contain any hints as to the right answer. Distracters are meant to induce you to an incorrect choice, not give you clues as to the correct one.

4. They will seem plausible and attractive to the uninformed. If you are not sufficiently familiar with a topic, you may well find that all of the options look good.

5. They will be similar to the correct answer in construction and length. Trying to "psych-out" the question by looking for flaws in its construction is not a useful strategy.

Questions that do not adhere to these rules are not used on the exam. All options are meant to distract you, but often one of the distracters will seem better than the others, the so-called preferred distracter. While still incorrect, this is the wrong answer chosen most often. Preferred distracters are why you can often get yourself down to two choices: the correct answer versus the preferred distracter.

USMLE Primacy and Recency Effects

Primacy and Recency Effects—getting the right cognitive set
Information that appears early in a question stem and information that appears at the end of the question stem exert a strong influence on the student answering the question. Early and late information forms the student’s cognitive set, making finding the correct answer either easier or harder. Information at the start of the question stem has a primacy effect, controlling our thinking by determining what we start thinking about. Information at the end of the question stem has a recency effect, controlling our thinking by providing the jumping off point to select the correct answer.

If the key information for the question appears in the primacy or recency spots, the student will be led to the correct answer. The difficulty for the examinee comes when the key information lies some where in between. Primacy and recency information can blind students to other essential content. Students sometimes fixate on early or late information and in so doing, miss other important information given in the question stem.

For example, if a question begins by describing a patient as having a generalized anxiety disorder, all of the information which will tend to be seen in that context, even though the anxiety disorder diagnosis may not be directly pertinent to the correct answer for the question!

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