Moreover, we have used the model to detect subspecies differences in the maze performance of rats and to characterize the learning deficits in honey bees exposed to agro chemicals.The remainder of this article describes the mathematical foundation of our model and finishes with an example of how the model is used in practice. We would like to note that the material is presented in detail to provide the reader with a full description of how the model is used. The raw learning data, along with the calculated coefficients, are provided for each individual in table form. Figures are also provided describing the quality of the model fit with actual data. The senior authors would be glad to assist any researcher in applying the model. Previously, modeling of the learning curves was applied to raw learning data from CVLT/CVLT-II,List A, and CVLT-C. However, the use of the mathematical model imposes certain additional requirements for carrying out the free recall memory test in order to obtain accurate information about the memory state of the examinee.
In connection with the above, we identified a need to develop our own version of the free recall memory test that meets all of the necessary requirements to ensure the effectiveness of mathematical modeling.The first requirement concerns the size of the word list. How should the optimal number of words for the list be chosen? We found that healthy females could recall up to 12 – 13 words from a list. Therefore,the list must include at least 13 words to correctly assess levels of short-term memory. This means that ten words, which are used in some tests, may not be enough to assess short-term memory. On the other hand,what size of a list should be used for correct assessment of long-term memory and to prevent the so-called“ceiling effect”? Obviously, the quantity of words in a list should exceed 13 words for the correct assessment of long-term memory. The CVLT/CVLT-II, List A includes 16 words, but the authors of the test did not explain their choice. We might consider the explanation to be that they used four semantic categories with four words in each category. Similarly, Zim prich and Rast used a list of 27 meaningful, but unrelated,two to three syllable German words.From our point of view, the size of a list depends on the group of people for whom the test is intended.If the task is to study how many words healthy persons can learn and recall, a list can be increased up to 27 words.
If the memory test is developed for the assessment of marijuana users with initial signs of memory impairment, from our point of view, 16 – 20 words is enough. If a list exceeds 20 words, its use in marijuana users might lead to fatigue and even have some neurological consequences. Thus, the senior authors constructed a word list consisting of 16 words, taken from four semantic categories: vegetables,animals, ways of traveling, and furniture, in such a way that no two words are from the same semantic category. Moreover, no two words from the same semantic category were placed side by side.The second requirement deals with deciding on the optimal number of trials.The CVLT/CVLT-IIuses five trials. However, many individuals do not have time to reach their asymptotic level of correctly recalled words with five presentations of a list of words. As a result, coefficient B4 returns overestimated values, which requires an additional correction. Alternatively, some tests use too many trials, for example,ten trials are used in Luria’s memory test. This is why the senior authors selected six trials, as this is sufficient to assess the asymptotic level of B4 value without producing fatigue.The third requirement deals with the order of words during the second and subsequent presentation of the list. In CVLT/CVLT-II, the order of words in List A is constant during each trial to assess primacy/recency recall.
However, from a modeling point of view, it is desirable to let the participant learn each word from the list equally. That is why the order of words in the list is changed on each trial. Note that Zimp rich and Rast used the same approach. In principle, we moved each word from its initial position in the list to an opposite position, for example, from the beginning or the end region of the list to the middle region and vice versa.The fourth requirement deals with so-called “item-specific” practice that refers to the learning of actualcontent from one administration of the test to the next . The item-specific practice can be mitigated via the use of alternate test forms with different lists of words. That is why six lists of16 words were constructed from the same semantic categories. A total of six lists allows avoiding“item-specific” practice during six test/retest administrations for each participant.The fifth requirement deals with testing/retesting of the participant. The learning curves of the same participant are never identical during retesting.