Differential Linguistic Recall Effects in the California Verbal Learning Test in Healthy Aging and Alzheimer's Dementia: Analysis of Routine Diagnostic Data.

Abstract

Psycholinguistic evidence suggests that certain word characteristics might influence recall rates in word-list learning tests. These effects were investigated in the German California Verbal Learning Test (CVLT-G) in a clinical setting. Subjects were memory clinic patients without cognitive diagnosis (N=45) and with dementia of the Alzheimer type (DAT) (N=48) matched for age, sex, depressive symptoms, and education. The CVLT-G's words were analyzed with regard to length, frequency, and neighborhood size and dichotomized into low and high value groups. For each linguistic variable, a 2 (diagnosis: control vs. DAT)×3 (time: Trial 1 vs. Trial 5 vs. Long Delay Free Recall)×2 (linguistic: low vs. high) repeated measures analysis of variance (RM-ANOVA) was conducted. RM-ANOVAs revealed a main effect for frequency, F(1,91)=21.03, p<0.001, and interactions between time and frequency, F(1.97,179.09)=5.18, p=0.007, and diagnosis and neighborhood, F(1.77,161.23)=13.60, p<0.001. High-frequency words were better recalled at Trial 5 (Cohen's d=0.37) and long delayed free recall (d=0.16) and learning from Trials 1 to 5 was better for high-frequency words (d=0.39). Controls recalled large neighborhood words better whereas the opposite was true for persons with DAT (d=0.76). Frequency and neighborhood size seem to influence learning and retention in the CVLT-G with neighborhood size producing opposed effects for persons with and without DAT. These results are in line with international experimental studies and likely not specific to the German language. Potential diagnostic implications and possibilities for test construction and interpretation are discussed.