Abstract
Objective
Examine whether verbal abilities may help explain the learning strategies people employ when completing a short-term verbal memory task.
Methods
The assessment records of 296 American Veterans with diverse neuropsychiatric conditions were analyzed using Exploratory Factor Analyses. There were no exclusion criteria. All participants completed the Benton Serial Digit Learning Test – 9 Digits (SDL-9) and Visual Naming (VisNam), Sentence Repetition (SenRep), Controlled Word Association (COWA), and Token Tests of the Multilingual Aphasia Examination (MAE). Individual assessment instruments were factored using Principal Component Analyses (PCA). A three-factor solution of the SDL-9 was co-factored with the verbal components of the MAE to identify common sources of variance.
Results
A three-factor solution of the SDL-9 separated trials into three overlapping factors consisting of early (SDL-9_Early), middle (SDL-9_Middle), and late (SDL-9_Late) trials. Co-factoring the three new scales with the verbal components of the MAE produced a four-factor model explaining 67.85% of the shared variance: 1) SenRep loaded with SDL-9_Early, 2) COWAT loaded with SDL-9_Middle and SDL-9_Late, 3) Token loaded with SDL-9_Late, and 4) Vis Nam loaded with SDL-9_Late.
Conclusions
The results suggest that individuals may engage verbal abilities differently as they progress from simpler to more difficult verbal short-term memory tasks. It appears performance in early trials is mostly associated with rote repetition and performance on middle trials is mostly associated with verbal fluency, while performance on the late trials is associated with a combination of verbal fluency, auditory comprehension, and conceptual organization/naming. This may therefore indicate a shift in learning strategy to meet increased cognitive demands.
Modulation of alpha power at encoding and retrieval tracks the precision of visual short-term memory
