Schizophrenics learn surface but not abstract structure in a serial reaction time task.

We investigated the hypothesis that explicit cognitive processing is impaired in schizophrenia, while implicit processing is left largely intact, using a single sequence learning paradigm that simultaneously measures surface and abstract structure learning. Surface structure is the serial order of sequence elements. Abstract structure is defined in terms of the relationships between repeating elements. Sequences ABCBAC and DEFEDF thus share the same abstract structure, with different surface structures. Learning abstract structure requires explicit processing, while surface structure can be learned in implicit conditions. We predict however, that in explicit conditions, schizophrenics should learn surface structure but not abstract structure. Indeed, schizophrenic patients learned surface structure, but failed to learn abstract structure, demonstrating that implicit sequence processing is spared in schizophrenia while explicit sequence processing is impaired.