Computation and Analysis of Effect Sizes
Because of the range of methodologies used across studies, we used a randomeffects model, and conducted statistical analyses using the Comprehensive Metaanalysis, Version 2 (CMA) program (Borenstein, Hedges, Higgins, & Rothstein, 2005). A randomeffects model is deemed appropriate as participant samples and experimental factors across studies cannot be assumed to be functionally equivalent. Thus, it cannot be assumed that all effect sizes will share a common effect. Cohen’s d values are reported here as calculated by the CMA program as a measure of effect size. Cohen’s d’s between .20 and .50 indicate small effects, d’s between .50 and .80 indicate moderate effects, and d’s greater than .80 indicate large effects (Cohen, 1988).
Overall Effects
The overall effects matched those previously reported by Powers and colleagues (2013): a metaanalysis at the level of studies (N = 46) generated a small to medium mean effect size, d = .48, 95% CI [.35, .60], with marginal heterogeneity observed across studies, Q (45) = 58.26, p = .089, I^{2} = 23.78. A metaanalysis at the level of comparisons (N = 265) generated a small mean effect size, d = .30, 95% CI [.23, .37], with significant heterogeneity, Q (264) = 684.80, p = .001, I^{2} = 61.45.
Training game type, analyzed at the level of comparisons, moderated effect sizes, Q (6) = 35.33, p = .001 (see Table 21.2). All game types showed small effects except for Wii games, which showed large effects, and strategy/roleplay games, which showed negligible, nonsignificant effects.
Informationprocessing domain, analyzed at the level of comparisons, moderated effect sizes, Q (3) = 29.93, p = .001 (see Table 21.3). A large effect of training was observed in the domain of motor skills, but this result was based on only 16 comparisons from seven studies. Small effects of training were observed in domains of perceptual processing and spatial imagery; in contrast, negligible effects were found for executive functions.
Table 21.2 Summary of Effect Sizes Moderated by Training Game Type at the Level of Comparisons
Training game type 
Cohen’s d 
95% CI 
Z 
pvalue (Z) 
k 
N Q (df) pvalue (Q) 
ArcadeStyle 
.31 
[.20, .42] 
5.33 
.001 
59 
2514 
FirstPerson Shooter 
.23 
[.07, .39] 
2.78 
.005 
61 
2018 
Puzzle (NonTetris) 
.31 
[.001, .63] 1.95 
.051 
23 
923 

Sport/Racing 
.36 
[.13, .60] 
3.02 
.003 
9 
366 
Strategy/RolePlay 
.06 
CO t—1 LO О 
1.07 
.284 
35 
1334 
Tetris 
.28 
[.13, .44] 
3.50 
.001 
51 
1507 
Wii 
.95 
[.66, 1.23] 
6.58 
.001 
20 
684 
Betweenclasses effect 
35.33 (6) .001 
Table 21.3 Summary of Effect Sizes Moderated by InformationProcessing Domain at the Level of Comparisons
Domain 
Cohen’s d 95% CI 
Z 
pvalue (Z) 
k 
N Q (df) 
pvalue (Q) 
Executive Functions 
.15 [.04, .25] 
2.68 
.007 
96 
3848 

Motor Skills 
.76 [.54, .98] 
6.65 
.001 
15 
627 

Perceptual Processing 
.32 [.15, .49] 
3.71 
.001 
71 
2216 

Spatial Imagery 
.42 [.32, .52] 
8.46 
.001 
79 
2655 

Betweenclasses effect 
28.93 (3) 
.001 