Insufficient automatization of the alphabet may falsely impair performance on the Trail Making Test among persons with dyslexia or persons not accustomed to the Latin alphabet. We analyze whether writing the alphabet on top of the test sheet changes performance in these risk groups, and whether alphabet support reduces the complexity of the set-shifting task.One-hundred and seventy patients referred to neuropsychological assessment participated and were given both a TMT-version offering alphabet support and the D-KEFS TMT. The discrepancy between the D-KEFS subtask where lines are drawn successively between numbers only, and the task where lines are drawn between letters only, was operationalized as measuring insufficient alphabet automatization.Both the possible dyslexia group, and persons taught to read with another alphabet, had a larger discrepancy score than the remaining sample. Regression analyses showed that the discrepancy scores explained 3.4% of the variance beyond age and speed when giving alphabet support. The corresponding percentage for the D-KEFS Switching task was 17.5%. The findings indicate that alphabet support alleviated effects of non-automatization. The TMT-B-NR: TMT-A ratio score was equivalent to what is found when not applying alphabet support, showing that alphabet support did not contaminate the test as a EF-measure.
Keywords: D-KEFS; Trail Making Test; driving assessment; dyslexia; ethnic minority studies.