Background: Psychotic patients consistently demonstrate 'jumping to conclusions' (JTC) on a cognitive task compared to matched controls. This study aimed to examine this phenomenon in first-episode psychosis patients and controls, and assess whether those who show the bias have worse IQ, clinical and cognitive insight. Methods: The study used a case-control design to assess differences in reasoning, IQ and cognitive insight between patients and controls. Differences in clinical insight in patients with and without JTC were also assessed. First-presentation psychotic patients (N=62) were recruited to the Genetics and Psychosis (GAP) study. A healthy comparison group (N=57) was recruited from the same area. The beads task (JTC) was administered. Subjects completed the Beck Cognitive Insight Scale and a neuropsychological battery. Patients were assessed with the clinician-rated Schedule for the Assessment of Insight. Chi-squared tests, independent samples t-tests and binomial logistic regression were used in analysis. Results: Patients demonstrated more JTC responses than controls (45.2% vs. 24.6%, p=0.019). Patients and controls who showed JTC bias had lower IQ (p<0.001), but not cognitive insight. Patients who showed JTC bias had lower 'recognition of illness' (p=0.037). Binary logistic regression suggested that IQ predicts whether subjects would show JTC better than case-control status. Discussion: JTC bias is linked to several other 'deficits'. Specifically they show lower IQ and clinical insight. IQ is the best predictor of showing JTC bias. Further work should investigate which specific cognitive domains are linked to JTC, and whether these overlap with deficits seen with clinical insight.