Vigilance of performance of mildly mentally retarded children.

The contribution of developmental factors to the vigilance performance of mildly mentally retarded children was investigated by comparing their vigilance performance with that of nonretarded children of the same CA and with younger nonretarded children of about the same MA. The retarded children showed an earlier and faster decline in vigilance performance than did the CA control group. This result was similar to that of Semmel (1965), but contrasted with that of Kirby, Nettlebeck, and Bullock (1978), who found no such difference in vigilance performance when comparing mildly mentally retarded and nonretarded adults. The MA control group performed in a similar way to the retarded children, suggesting that the more rapid decline in vigilance performance was largely a developmental phenomenon.