Immediate Memory Index Research Articles

Parsimonious prediction of Wechsler Memory Scale, Fourth Edition scores: Immediate and delayed memory indexes

Research on previous versions of the Wechsler Memory Scale (WMS) found that index scores could be predicted using a parsimonious selection of subtests (e.g., Axelrod & Woodard, 2000). The release of the Fourth Edition (WMS–IV) requires a reassessment of these predictive formulas as well as the use of indices from the California Verbal Learning Test–II (CVLT–II). Complete WMS–IV and CVLT–II data were obtained from 295 individuals. Six regression models were fit using WMS–IV subtest scaled scores—Logical Memory (LM), Visual Reproduction (VR), and Verbal Paired Associates (VPA)—and CVLT–II substituted scores to predict Immediate Memory Index (IMI) and Delayed Memory Index (DMI) scores. All three predictions of IMI significantly correlated with the complete IMI (r = .92 to .97). Likewise, predicted DMI scores significantly correlated with complete DMI (r = .92 to .97). Statistical preference was indicated for the models using LM, VR, and VPA, in which 97% and 96% of the cases fell within two standard errors of measurement (SEMs) of full index scores, respectively. The present findings demonstrate that the IMI and DMI can be reliably estimated using two or three subtests from the WMS–IV, with preference for using three. In addition, evidence suggests little to no improvement in predictive accuracy with the inclusion of CVLT–II indices.

Comparability of the GMI and DMI for the WMS-III

This study compared the new Delayed Memory (DMI) with the General Memory (GMI) index of the WMS-III using 134 inpatients with substance abuse disorders. The WMS-III Immediate Memory Index (IMI) and the GMI are not parallel because the latter includes Auditory Recognition Delayed. A solution to this dilemma is the DMI, in that it directly parallels the original IMI. The GMI and DMI scores were highly correlated, r = .98, and mean values differed by<1 point (90.77 and 90.66, respectively). Difference score comparisons (i.e., IMI-GMI with IMI-DMI and FSIQ-GMI with FSIQ-DMI) yielded similar results (ts<1). Case-by-case analyses demonstrated concordance rates of 99% for the IMI-GMI and IMI-DMI comparisons and 94% for the FSIQ-GMI and FSIQ-DMI contrasts.

Development of a New Delayed Memory Index for the WMS-III

This paper presents the Delayed Memory Index (DMI) as an alternative to the General Memory Index (GMI) of the Weschler Memory Scale–Third Edition (WMS–III). The WMS-III Immediate Memory Index (IMI) and the GMI are not parallel in structure, making a direct comparison between these index scores (i.e., immediate vs. delayed memory variables) difficult. The IMI is composed of the sum of scaled scores of four subtests (Logical Memory I, Verbal Paired Associates I, Faces I, and Family Pictures I) while the GMI is composed of the sum of scaled scores of five subtests (Logical Memory II, Verbal Paired Associates II, Faces II, Family Pictures II and Auditory Recognition Delayed). Inclusion of Auditory Recognition Delayed in the GMI is also problematic as it is highly skewed and limited by extreme ceiling effects (see Tulsky, Chiaravalloti, Palmer, & Chelune, 2003). To remedy these problems, we present a new index score that does not include auditory recognition, the Delayed Memory Index. Normative tables for the new Delayed Memory Index based on the inclusion of the Faces subtest, or alternatively the Visual Reproduction subtest, are presented, and initial estimates of their psychometric properties are described.