Kavale and Forness (1983) reviewed the difference in achievements related to those students classified as brain injured and those with difficulties more related to familial-cultural factors. The 26 studies yielded 241 effect sizes and an average of d = 0.10 between the two groups—with differences related to perceptual-motor (d = 0.11), cognition (d = 0.14), language (d = 0.10), behavior (d = 0.09), and intelligence d = 0.05—so little difference was established.
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