Box-and-whisker plots (A and B) of each cognitive subtest by birth weight z score category. All z scores are adjusted to population norms. Light gray is <−2; medium gray is ≥−2, <−1; and dark gray is ≥−1. The central line in the box indicates the median (50th percentile), whereas the top of the box indicates the 75th percentile, and the bottom of the box indicates the 25th percentile. If ELGAN had the expected normal distribution of term children, the middle of the box would be at z score = 0, and the upper and lower ends of the box would be at z score = 1 and z score = −1, respectively. AA, auditory attention; AS, animal sorting; AW, arrows; GEO, geometric puzzles; INI, inhibition inhibition; INN, inhibition naming; INS, inhibition switching; LC, listening comprehension; NO, numerical operations; NV, nonverbal reasoning; OE, oral expression; PwD, pseudoword decoding; RS, auditory response set; Sp, spelling; V, verbal; VP, visuomotor precision; WM, working memory; WR, word reading.