Cognition test battery: Adjusting for practice and stimulus set effects for varying administration intervals in high performing individuals.

Introduction: Practice effects associated with the repeated administration of cognitive tests often confound true therapeutic or experimental effects. Alternate test forms help reduce practice effects, but generating stimulus sets with identical properties can be difficult. The main objective of this study was to disentangle practice and stimulus set effects for , a battery of 10 brief cognitive tests specifically designed for high-performing populations with 15 unique versions for repeated testing. A secondary objective was to investigate the effects of test-retest interval on practice effects.

Methods: The 15 versions of were administered in three groups of 15-16 subjects (total N = 46, mean±SD age 32.5 ± 7.2 years, range 25-54 years, 23 male) in a randomized but balanced fashion with administration intervals of ≥10 days, ≤5 days, or 4 times per day. Mixed effect models were used to investigate linear and logarithmic trends across repeated administrations in key speed and accuracy outcomes, whether these trends differed significantly between administration interval groups, and whether stimulus sets differed significantly in difficulty.

Results: Protracted, non-linear practice effects well beyond the second administration were observed for most of the 10 tests both in accuracy and speed, but test-retest administration interval significantly affected practice effects only for 3 out of the 10 tests and only in the speed domain. Stimulus set effects were observed for the 6 tests that use unique sets of stimuli. Factors were established that allow for correcting for both practice and stimulus set effects.

Conclusions: Practice effects are pronounced and probably under-appreciated in cognitive testing. The correction factors established in this study are a unique feature of the battery that can help avoid masking practice effects, address noise generated by differences in stimulus set difficulty, and facilitate interpretation of results from studies with repeated assessments.