Table 1. Behavioral measures and in-scanner task performance.

Socio-economic status was quantified per the Barratt Simplified Measure of Social Status (BSMSS), which assigns codes for number of years of maternal education (18 = completed college, possible scores range from 3 to 21). Nonverbal IQ was assessed using the Kaufman Brief Intelligence Test (KBIT-2 Matrices); Letter ID and Word ID are subtests of the Woodcock Reading Mastery Test (WRMT-R/NU). Task performance accuracy (percent correct) on the one-back tasks was measured by number of (hits + correct rejections) / total stimuli.

	Mean ± SD	Range
Age (months)	66.46 ± 3.29	62 – 74
Mother’s Education (BSMSS score)	18.91 ± 2.35	12 – 21
Nonverbal IQ
Standard score	103.96 ± 7.38	90 – 118
Letter ID
Raw score	32.04 ± 5.72	6 – 41
Standard score	110.63 ± 8.40	88 – 130
Word ID
Raw score	13.52 ± 18.89	0 – 67
Standard score	112.92 ± 29.09	80 – 175
In-scanner task accuracy (percent correct)
Letters	94.83 ± 3.87	80 – 100
False fonts	94.53 ± 3.77	83.34 – 100
Faces	96.18 ± 2.87	88.34 – 100