Table 1. Working Memory Spans and Speed of Processing.

	First Grade	Fifth Grade	Gains
	M (SD)	M (SD)	M	SD	d	d2
Central executive	2.15 (.55)	3.04 (.56)	0.89	0.51	1.6	1.7
Phonological memory	3.30 (.62)	3.99 (.63)	0.70	0.54	1.1	1.1
Visuospatial memory	2.79 (.63)	4.21 (.82)	1.42	0.76	2.3	2.4
Mazes Memory	2.10 (.78)	4.13 (1.13)	2.03	1.14	2.6	2.8
Block Recall	3.48 (.80)	4.29 (.85)	0.81	0.92	1.0	1.2
Numeral RAN RT	42.2 (12.1)	25.8 (5.3)	16.5	10.5	1.4	–
Letter RAN RT	40.2 (11.8)	25.2 (5.2)	15.0	10.4	1.3	–

Note: Span scores are reported for the working memory measures and reaction time (RT) in seconds for the rapid automatized naming (RAN) measures. d = effect size, (|M₅–M₁|)/SD₁, where M₅ and M₁ are the respective means for fifth and first grade, and SD₁ is the standard deviation for first grade. d₂ = effect size based on total correct. In first and fifth grades respectively, the central executive was correlated with phonological (rs = .51,.60) and visuospatial (r = .48,.57) memory spans (ps = .0001), which in turn were correlated with each other (r = .25,.45, ps = .0008).