A Comparison of Laboratory and Clinical Working Memory Tests and Their Prediction of Fluid Intelligence

Abstract

The working memory (WM) construct is conceptualized similarly across domains of psychology, yet the methods used to measure WM function vary widely. The present study examined the relationship between WM measures used in the laboratory and those used in applied settings. A large sample of undergraduates completed three laboratory-based WM measures (operation span, listening span, and n-back), as well as the WM subtests from the Wechsler Adult Intelligence Scale-III and the Wechsler Memory Scale-III. Performance on all of the WM subtests of the clinical batteries shared positive correlations with the lab measures; however, the Arithmetic and Spatial Span subtests shared lower correlations than the other WM tests. Factor analyses revealed that a factor comprising scores from the three lab WM measures and the clinical subtest, Letter-Number Sequencing (LNS), provided the best measurement of WM. Additionally, a latent variable approach was taken using fluid intelligence as a criterion construct to further discriminate between the WM tests. The results revealed that the lab measures, along with the LNS task, were the best predictors of fluid abilities.

Figure 1

Latent variable model representing the correlated two-factor model of working memory. In all figures, the circles represent latent constructs, and the squares represent the observed variables. The path coefficients appearing on the arrows from the latent construct to the observed variables are standardized values, comparable to standardized regression weights and reflect the factor loadings of the observed variables (Kline, 2005). All paths are significant at p < .05. Italicized numbers next to the observed variables represent the squared multiple correlations. The double-headed curved arrow represents the correlation between the two WM constructs. The three laboratory measures were Ospan = Operation Span Score; Lspan = Listening Span Score; Lag = N-back or Lag Score; The clinical measures from the WAIS-III and WMS-III were LNS = Letter Number Sequencing raw score; Arith = Arithmetic raw scores; Spatial Span = raw scores from the total of the forward and backward scales of the spatial span task; Digit span = raw scores from the total of the forward and backward scales of the digit span task.

Figure 2

Latent variable model representing the hybrid model of the working memory construct. Numbers on the arrows between the latent variable and the observed variables reflect the loadings for each task; all paths are significant at p < .05. Italicized numbers next to the observed variables represent the squared multiple correlations. The three laboratory measures were Ospan = Operation Span Score; Lspan = Listening Span Score; Lag = N-back or Lag Score; The clinical measure from the WAIS-III was LNS = Letter Number Sequencing raw score.

Figure 3

The path between the latent variables represents the strength of the relationship between the constructs. Italicized numbers next to the observed variables represent the squared multiple correlations. A) Prediction of gF from the variables representing the hybrid model of the WM construct. Ospan = Operation Span Score; Lspan = Listening Span Score; Lag = N-back or Lag Score; LNS = Letter Number Sequencing raw score; Raven = total score from the Raven’s Advanced Progressive Matrices; Block = raw score from the Block Design task; Matrix = raw score from the Matrix Reasoning task.