A study published in the journal Brain offers new insights into the development of delusions — false beliefs that are rigidly held with strong conviction despite contradictory evidence. Based on the findings, the researchers framed delusions as “sticky” beliefs that tend to evolve in an unusually slow manner.
An estimated 80-90 percent of patients with schizophrenia and other psychotic disorders experience delusions, but scientists are still unsure of what causes these often distressing and debilitating beliefs.
A long-held hypothesis is that delusions are caused by alterations in one’s ability to make inferences. An inference is a person’s “best guess” based on all available evidence and reasoning.
Delusional and delusion-prone individuals may have a tendency to gather less data before forming beliefs. Other experiments have suggested that other cognitive processes may be involved.
“The experiments typically used to understand the link between inference and delusions have focused on cognitive and decision-making skills, but they haven’t conclusively shown a link between inference-making and delusion severity,” said Guillermo Horga, M.D., Ph.D., the Florence Irving Assistant Professor of Psychiatry at Columbia University Vagelos College of Physicians and Surgeons and lead author of the paper.
“We developed a novel experiment to determine whether delusions stem from abnormalities in inference.”
In the experiment, researchers at Columbia University and New York State Psychiatric Institute asked 26 adults with schizophrenia, including 12 who were being treated with antipsychotic medications, and 25 healthy individuals to draw beads from one of two hidden jars.
Based on the type of bead, the participants must guess from which jar the beads are being pulled. For example, one jar might hold mostly green and a few pink beads, while another jar holds the opposite ratio.
Participants were given money, which could be used to bet on which jar the bead came from. The participants were told that drawing additional beads would help them bet correctly, though it would diminish their winnings. Throughout the experiment, they were asked to rate the odds of their bet on the identity of the jar.
“We found that patients who experienced more severe delusions tended to seek more information in the task before making a guess than their less-delusional counterparts. This is a truly novel finding, and it helps confirm the fact that rigidity is an important part of delusional beliefs,” says Horga.
Using computational modeling, the team developed a framework casting delusions as “sticky” beliefs that evolve in an unusually slow way. This may explain why delusional patients seek more information than non-delusional individuals. It could also help to identify new treatment approaches, such as neurostimulation of the prefrontal brain areas involved in updating beliefs, or cognitive training to shape inference-making.
“Previous work suggested that psychotic patients ‘jump to conclusions,’ but in our study we saw that individuals with more delusional beliefs took more beads from the jar before they made up their minds,” Horga said.
“While participants with schizophrenia jumped to conclusions more than healthy individuals, delusions specifically were associated with slower change in individuals’ beliefs.”