Semantic knowledge (long-established knowledge about objects, facts, and word meanings) is known to be impaired in schizophrenia. It has been hypothesized that language disorder in schizophrenia is linked both to executive and semantic dysfunctions.

To examine this hypothesis we assessed 32 patients with schizophrenia (with and without formal thought disorder) and 30 matched normal controls. We compared the performances obtained by the two groups on the tests that evaluate executive functions (WCST) and semantic knowledge (Pyramids and Palm Tree Test). Test of verbal fluency were also applied.

Patients generally performed at a lower level than controls. Patient with thought disorder performed at a lower level on tests sensitive to executive dysfunction and semantic impairments.

The results provide support for a dysexecutive hypothesis of formal thought disorder in schizophrenia and semantic processing.