Stimulus overselectivity: a common feature in autism and mental retardation.

Groups of children with different IQ levels were trained to discriminate between stimulus cards containing two or more pictures. In subsequent testing the pictures were presented singly in order to determine how many pictures the child had responded to during discrimination training. The data showed that the lower the IQ, the fewer pictures the child responded to. We speculated that intellectually retarded functioning may be related to problems in overselective attention; the lower a person's IQ level, the less of the environment becomes functional in controlling his behavior.