Learning problems, delayed development, and puberty

Abstract

Language-based learning disorders such as dyslexia affect millions of people, but there is little agreement as to their cause. New evidence from behavioral measures of the ability to hear tones in the presence of background noise indicates that the brains of affected individuals develop more slowly than those of their unaffected counterparts. In addition, it seems that brain changes occurring at approximately 10 years of age, presumably associated with puberty, may prematurely halt this slower-than-normal development when improvements would normally continue into adolescence. The combination of these ideas can account for a wide range of previous results, suggesting that delayed brain development, and its interaction with puberty, may be key factors contributing to learning problems.

Fig. 1.

(a and b) Average tone level required by listeners with LPs and controls to just detect a tone in the five masking conditions (rows; see schematics at far right). LP listeners (open squares) are compared with controls (filled squares) of the same age (a) and with controls ≈4 years younger (b). Between-group differences: ^**, P < 0.01; ^*, P < 0.05; n.s., P > 0.05. Error bars indicate ±SEM. (c) Effect size indices (d) on the same conditions calculated between LP listeners and (i) same-age controls (black bars), (ii) controls ≈2 years younger (hashed bars), and (iii) controls ≈4 years younger (white bars). SPL, sound pressure level.

Fig. 2.

Effect size indices (d) calculated between adults with LPs and adult controls in each of the five conditions (black bars, replotted from Fig. 1) and the age at which listeners in each group reached the performance of adults in that group.