Table 1.

Participant demographic and related information

	Grey matter		White matter
	Bilinguals	Monolinguals	Bilinguals	Monolinguals
n	141	570	127	510
n (by age range)
3–6	13	97	11	84
6.1–10	42	171	37	154
10.1–14	24	136	20	125
14.1–18	33	97	31	89
18.1–21	29	69	28	58
Mean age (SD)	12.48 (5.11)	11.15 (4.87	12.73 (5.11)	11.15 (4.79)
Females/males	77/64	283/287	67/60	251/259
Parental education level
1 = Less than 7 years of school	4	0	4	0
2 = 7–9 years of school	2	2	2	2
3 = 10–11 years of school	2	8	0	7
4 = High school graduate	10	61	9	58
5 = 1–3 years of college (also business school)	33	147	31	130
6 = 4-year college graduate	33	164	30	148
7 = Professional degree	57	188	51	165
Household income
1 =  < $5,000	8	14	6	13
2 = $5,000—9,999	3	20	3	18
3 = $10,000—19,999	6	37	5	33
4 = $20,000—29,999	6	44	6	42
5 = $30,000—39,999	10	41	9	37
6 = $40,000—49,999	10	33	8	29
7 = $50,000—99,999	45	164	43	144
8 = $100,000—149,999	23	120	20	110
9 = $150,000—199,999	12	53	9	45
10 = $200,000—249,999	10	15	10	12
11 = $250,000—299,999	4	12	4	12
12 = $300,000 +	4	17	4	15

For more information on each of the variables above (e.g., parental education level, household income) see Akshoomoff et al. (2014); Jernigan et al. (2016). The age bands are provided for informational purposes; all analyses included age as a (nonlinear) continuous variable