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. Author manuscript; available in PMC: 2015 Dec 22.
Published in final edited form as: JAMA Pediatr. 2015 Sep;169(9):822–829. doi: 10.1001/jamapediatrics.2015.1475

Table 3.

Socioeconomic Status, Brain Development, and WJ-III Scores in the National Institutes of Health Magnetic Resonance Imaging Study of Normal Brain Developmenta

Variable Frontal Lobe, β Temporal Lobe, β Hippocampus, β Amygdala, β
WJ-III math computation (n = 87)
 Direct effect −6.18 −6.15 −6.27 −6.64
 Indirect effect −0.95 −1.01 −0.87 −0.54
  Percentile 95% CI −1.72 to −0.32 −1.78 to −0.38 −1.59 to −.28 −1.26 to 0.02
  Bias-corrected 95% CI −1.83 to −0.39 −1.83 to −0.41 −1.66 to −.33 −1.35 to −0.03
 Indirect/total effect 0.13 0.14 0.12 0.02
WJ-III letter-word identification (n = 798)
 Direct effect −3.83 −3.65 −3.97 −4.05
 Indirect effect −0.47 −0.66 −0.33 −0.26
  Percentile 95% CI −0.92 to −0.12 −1.22 to −0.24 −0.77 to −0.02 −0.65 to 0.01
  Bias-corrected 95% CI −0.98 to −0.14 −1.32 to −0.28 −0.83 to −0.05 −0.72 to −0.01
 Indirect/total effect 0.11 0.15 0.08 0.06
WJ-III passage comprehension (n = 797)
 Direct effect −5.15 −4.94 −5.07 −5.43
 Indirect effect −0.4 −0.61 −0.49 −0.13
  Percentile 95% CI −0.83 to −0.08 −1.11 to −0.20 −0.99 to −0.11 −0.43 to 0.05
  Bias-corrected 95% CI −0.91 to −0.11 −1.20 to −0.25 −1.05 to −0.14 −0.52 to 0.01
 Indirect/total effect 0.07 0.11 0.09 0.02

Abbreviation: WJ-III, Woodcock-Johnson III Tests of Achievement.

a

Mediation analyses correspond to specifications in eTable 9 in the Supplement. Estimates of the direct and indirect (mediated through influence on structural brain development) effects of low income on a standardized test of achievement are shown. Mean (SD) tests scores are standardized (100 [15]). Standard errors have been bootstrapped. The 95% CIs were constructed using bootstrap resampling with 5000 iterations.