Background
Empirical studies of rationality (syllogisms) in patients with
schizophrenia have obtained different results. One study found
that patients reason more logically if the syllogism is presented
through an unusual content.

Aims
To explore syllogism-based rationality in schizophrenia.

Method
Thirty-eight first-admitted patients with schizophrenia and 38
healthy controls solved 29 syllogisms that varied in
presentation content (ordinary v. unusual) and validity (valid v.
invalid). Statistical tests were made of unadjusted and adjusted
group differences in models adjusting for intelligence and
neuropsychological test performance.

Results
Controls outperformed patients on all syllogism types, but the
difference between the two groups was only significant for
valid syllogisms presented with unusual content. However, when
adjusting for intelligence and neuropsychological test performance,
all group differences became non-significant.

Conclusions
When taking intelligence and neuropsychological performance
into account, patients with schizophrenia and controls perform
similarly on syllogism tests of rationality.