Assessment of stimulus overselectivity with tactile compound stimuli in children with autism.

Autistic and typical children mastered a simultaneous discrimination task with three sets of all-tactile compound stimuli. During training, responding to one stimulus (S+) resulted in rewards whereas responding to the alternative (S-) was extinguished. Test 1 was conducted with recombinations of S+ and S- elements. In Test 2, the test stimulus to which the child responded most in Test 1 was pitched against the training S+. In Test 1, all children responded exclusively to one test probe, spuriously implying stimulus overselectivity in both populations. However, in Test 2, the typical children responded mostly to the training S+ indicating control by both S+ elements; the autistic children responded to both stimuli indicating reduced control by the second S+ element (indicating overselectivity).