Figure 4. Illustration of a practice effect by examining longitudinal performance measures in patients with MS and cohabitants.

(A) Response time for each trial of the Trails A test performed by a participant pair (patient with multiple sclerosis [MS] and cohabitant) over the course of the study. Each point represents one trial. (B) Comparison of the first, last, and mean values for Trails A in study completers (n = 39). The last value appears to more closely match the mean than the first value does. (C, D) For each Trails A trial, a boxplot of the mean score for all MS (n = 22, C) and cohabitant completers (n = 17, D) is shown. These plots illustrate a gradual decrease in mean scores for all individuals over the duration of the study, with narrowing of the variance as the practice effect wanes. (E, F) Results of the spline analysis for Trails A reveal a longer practice effect, on average, in patients with MS (blue line) than in cohabitants (red line) (E). A similar effect is noted for responses on the 9-Hole Peg Test (F). (G) Illustration of the longitudinal performance of a patient with MS on the Trails A test. The individual scores (black dashes) appear to improve over time. The black solid line represents the inflection point analysis. After 7 trials, the practice effect appears to taper off. The location of the inflection point is determined by finding the maximal R-squared value (red line), which peaks around 7 trials for this individual.