Among the most difficult of concepts for me to memorize are what can be called binary symmetric definitions, in which Concept A is positive for category 1 and negative for category 2, and Concept B is negative for category 1 and positive for category 2, and the names for Concept A and B do not refer directly to their properties as relates to categories 1 or 2. As a result, the two definitions contain roughly the same words in a different order. The reason why I find this so difficult to remember is because the binding between name and definition is constantly disrupted by the symmetric definition, so that a one-to-one association is not forthcoming.
Here are two examples that I have had to deal with recently. Both are concepts which I have learned and forgotten at least three times each:
Non-competitive inhibitors change the total amount of receptors but do not alter the dissociation constant. Competitive inhibitors change the dissociation constant but do not alter the total amount of receptors.
Sensitivity refers to the ratio of true positives to the total of true positives and false negatives. Specificity refers to the ratio of true negatives to the total of true negatives and false positives.
In both cases, the group names are very similar and the definitions are symmetric or nearly symmetric. I heard one strategy proposed by Kaplan review lecturer Edward Goljan, who says the best method is to “remember one, and the other is the other.” To take this one step further, I have found that one efficient memory tool for this task to be the visual symbol.
Visual Symbols
Step 1: creation of a symbol which is 1-to-1 tightly associated with one of the Concepts, and which when properly and consistently analyzed, yields the properties of its definition. The symbol should be simplified maximally without losing key features.
On the left is a Scatchard plot for a non-competitive inhibitor, in which Kd is the slope and Rtot is the x-intercept. On the right is a picture of an ill person who is very sensitive to being poked.
Step 2: Associative (slow) recall phase – the first 3+ recalls will require reasoning through the symbol to arrive at the definition, and equally so for the definition of the opposite concept. The key goal of this phase is to strengthen the two associations which are correct, and weaken the two associations which are incorrect.
Step 3: True symbolism – the symbol eventually achieves immediate meaning without any reasoning or thought. Now, the moment the symbol is invoked by the concept name, the definition is linked instantaneously.
Parallel Ordering
Step 1: Select an order, e.g. (1) sensitivity (2) specificity
Step 2: Order the definitions or keywords in the same order, e.g. (1) proportion of healthy who test healthy (2) proportion of ill who test ill.
Step 3: Reinforce the ordering of the two separately, such that recall of either concept and either definition will have a natural 1:1 correspondence based on order.
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