Sunday, March 9, 2014

A New Trail Making Test

The Trail Making Test (TMT) is an oldie but a goodie. The paper-and-pencil neuropsychological measure consists of two parts: TMT-A is composed of numbers enclosed in circles, and the examinee is asked to simply connect the numbered circles in ascending order as quickly as possible. Part B has both letters and numbers, and examinees must connect "1" to "A," "A" to "2," "2" to "B," and so on. TMT-B has been considered one of the most sensitive indicators of overall brain impairment due to the multiple abilities it taps into (e.g., psychomotor speed, attention, working memory, visual scanning, mental flexibility).

On the other hand, the inclusion of the English alphabet has limited the use of the test to Western populations. Citing this along with evidence that individuals with less-education/MCI do not perform well on the TMT, researchers devised an alternative version of the TMT (Kim, Baek, & Kim, 2014). The TMT-B&W (black and white) replaces the letters of the original with a second, identical set of numbers which are enclosed in black circles instead of white ones. Instead of alternating between numbers and letters, examinees connect a white-circled number with it's black counterpart before moving onto the next number (see below). Part A is similar to the original TMT-A, but with all of the even numbers enclosed in black circles.

(from Kim, et al., 2014)

The authors administered the TMT-B&W and the original TMT (and some other neuropsych measures) to three groups of participants in South Korea, including a control group, patients diagnosed with mild cognitive impairment, and individuals with Alzheimer's Disease. Overall, a higher rate of individuals completed the TMT-B&W relative to the TMT (participants with lower education especially struggled to complete the TMT). Another interesting finding was that TMT-B performance only distinguished the AD group from the control group, while the TMT-B&W was able to distinguish between all three groups (i.e., control, MCI, and AD).

The latter result suggests the new version of the TMT may be more sensitive than the older one. However, it is unclear if this finding is due only to the struggles of the Korean participants to complete the original TMT (the control and MCI groups may have performed equally poorly due to not understanding the English alphabet). One would intuitively think this test would be less sensitive than the original TMT, because it appears easier. Specifically, the working memory demands of the TMT-B&W seem less demanding, given that examinees only have to remember the number that they just connected, rather than having to keep both numbers and letters in mind. I'd be interested in a factor analysis to see if the two measures are tapping into the exact same constructs.

The authors' goal was to provide a version of the TMT that could be used for non-Western and illiterate populations. The TMT-B&W certainly shows promise in this regard, as participants tolerated the test well and correlations with the original TMT and other measures demonstrated evidence of good construct validity. However, participants level of English fluency was not measured or described, so it's impossible to tell how much of a role this played in the study. Even in Western populations, the test may be useful with illiterate/poorly-educated individuals. A comparison of the two versions of the TMT in an English-speaking population would provide further information on whether this is the case.

Kim, H. J., Baek, M. J., & Kim, S. (2014). Alternative type of the Trail Making Test in nonnative English speakers: The Trail Making Test: Black & White. PloS One 9 (2), 1-6. 

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