Cognitive biases and speech connectedness in schizophrenia-spectrum disorders

Cognitive biases are systematic tendencies in the processing, selection and remembering of information. They are prevalent in schizophrenia-spectrum disorders (SSD) and are particularly associated with positive symptoms. The bias against disconfirmatory evidence (BADE) refers to a reluctance to integrate information that contradicts one’s beliefs and is associated with delusions. There is also some evidence of a link between BADE and formal thought disorder (FTD), though this relationship remains to be fully explored. FTD can be objectively quantified through speech via computerized processing of speech transcripts in both clinical and non-clinical samples. We sought to examine the relationship between BADE and speech connectedness in SSD patients (n = 30) and non-clinical controls (n = 15). We hypothesized that lower speech connectedness would be associated with greater severity of BADE. Speech graphs assessing language connectedness were generated from manually transcribed speech samples acquired during semi-structured interviews. The results supported previous findings of a greater BADE in patients relative to controls. While speech connectedness did not differ between patient and control groups, it was associated with positive symptoms (delusions, conceptual disorganization, and hallucinations) in patients. The link between BADE and FTD differed depending on whether patients had a non-affective or an affective SSD. In non-affective patients, higher BADE was associated with higher conceptual disorganization, measured via symptoms interviews, whereas higher BADE was associated with lower speech connectedness in affective patients. These findings support the notion that cognitive biases are linked to FTD, but suggest that non-affective versus affective diagnosis may affect the way in which this link is manifested.