TABLE 3.

Results of moderated mediation analysis

Predictor	Language composite score (Y)					Cognitive composite score (M)
	β	SE	LLCI	ULCI	p	β	SE	LLCI	ULCI	p
Left FA (X)	−0.23*	0.11	−0.45	−0.03	0.03	−0.18	0.14	−0.46	0.09	0.21
Childhood literacy score (W)	−0.18	0.12	−0.41	0.04	0.12	0.07	0.16	−0.25	0.35	0.63
Cognitive composite score (M)	0.61***	0.09	0.41	0.78	<0.001
Left FA × Childhood literacy score	−0.16	0.13	−0.38	0.15	0.22	0.33	0.19	−0.02	0.73	0.09

Indirect effect (a1 + a3*W)*b
Conditional indirect effects at different levels of childhood literacy score: (M ± 1 SD)	Bootstrapped indirect effect	Boot SE	Boot LLCI	Boot ULCI	p
−1 SD	−0.31	0.16	−0.65	−0.05	0.05
M	−0.11	0.09	−0.3	0.05	0.23
+1 SD	0.09	0.15	−0.17	0.4	0.52

Direct effect (c1 + c3*W)
Conditional direct effects at different levels of childhood literacy score: (M ± 1 SD)	Bootstrapped direct effect	Boot SE	Boot LLCI	Boot ULCI	p
−1 SD	−0.07	0.19	−0.52	0.24	0.71
M	−0.23*	0.11	−0.45	−0.02	0.04
+1 SD	−0.39**	0.14	−0.67	−0.1	<0.01

Note: Conditional direct and indirect effects at three levels of childhood literacy score (16th: −1 SD, 50th: M and 84th: +1 SD percentiles). Conditional effect is considered significant if 95% confidence intervals based on 5,000 bootstrap samples do not contain zero. Independent variable (X) = left caudate FA; mediating variable (M) = cognition composite score; dependent variable (Y) = language composite score; moderator (W) = childhood literacy score. Standardized regression coefficients are reported. Listwise N = 65. Bootstrap sample size = 5,000.

Abbreviations: FA, fractional anisotropy; LLCI, lower level confidence interval; SD, standard deviation; SE, standard error; ULCI, upper level confidence interval.

^* p < 0.05.

^** p < 0.01.

^*** p < 0.001.