Effect of test duration on age-related differences in Stroop interference.

The effect of test duration on age-related differences in Stroop interference was assessed in a large cross-sectional study involving 429 healthy subjects in four age groups (25-35 years, 40-50 years, 55-65 years, 70-80 years). The results show a clear effect of test duration on Stroop interference. The Stroop Color Word Test was run in two parts. The young group performed the first part relatively rapidly but became slower in the second part, whereas the old group showed the reverse effect. The two middle-aged groups did not show differences between the first and second parts of the test. The results are interpreted in terms of a deficit in response inhibition by a controlled processing strategy. A psychological interpretation of the study findings in terms of increased cautiousness appears less probable. The first part of the test, that is, an abridged version of the test, may prove superior to the regular version for both clinical and research purposes.