Trail Making Test, Stroop, and Verbal Fluency: Regression-Based Norms for the Icelandic Population

OBJECTIVE: The aim of this study was to construct regression-based norms for 3 executive-function tests: the Trail Making Test, Stroop, and Verbal Fluency. METHOD: A sample of 1,034 healthy Icelandic adults (18-64 years) was used to calculate predicted scores for test measures from all 3 tests, controlled for the effects of age, gender, and education, as well as the interaction between these variables. RESULTS: The 3 demographic variables showed significant effects on most test measures and were included in the final equation for estimating predicted scores. An older age and less education predicted worse cognitive performances in most cases, and women tended to outperform men. CONCLUSION: These results highlight the importance of adjusting for age, gender, and educational level when constructing normative data. Controlling for age alone may be insufficient or misleading in clinical-practice settings. A simple, user-friendly program for predicting executive-function test scores is provided.