New Haven, Conn. — Could complex beliefs like paranoia have roots in something as basic as vision? A new Yale study finds evidence that they might.
When completing a visual perception task, in which participants had to identify whether one moving dot was chasing another moving dot, those with greater tendencies toward paranoid thinking (believing others intend them harm) and teleological thinking (ascribing excessive meaning and purpose to events) performed worse than their counterparts, the study found. Those individuals more often — and confidently — claimed one dot was chasing the other when it wasn't.
The findings, published Dec. 17 in the journal Communications Psychology , suggest that, in the future, testing for illnesses like schizophrenia could be done with a simple eye test.
"We're really interested in how the mind is organized," said senior author Philip Corlett , an associate professor of psychiatry at Yale School of Medicine and member of the Wu Tsai Institute. "Chasing or other intentional behaviors are what you might think of as experiences perceived at a very high-level in the brain, that someone might have to reason through and deliberate. In this study, we can see them low down in the brain, in vision, which we think is exciting and interesting — and has implications for how those mechanisms might be relevant for schizophrenia."
Paranoia and teleological thinking are similar in that they are both misattributions of intention, but paranoia is a negative perception while teleological thinking tends to be positive. Both patterns of thinking are linked to psychosis and schizophrenia.
Hallucinations are associated with psychosis as well and are often about other people, said Corlett, suggesting there may be a social component to these visual misperceptions.
"So we wondered whether there might be something related to social perception — or misperception, what we refer to as social hallucination — that we could measure and that relate to these symptoms of psychosis," he said.
For the task, participants were shown dots moving on a screen. Sometimes one dot was chasing another; other times there was no chase. Across different trials of the task, participants had to say whether a chase was occurring or not.
Those with higher degrees of paranoia and teleological thinking (as measured through questionnaires) were more likely than others to say with confidence that a chase was happening when one wasn't. Essentially, they perceived a social interaction that wasn't occurring.
In additional experiments, the researchers asked participants to identify which dot was doing the chasing and which dot was being chased. In these results, paranoia and teleological thinking began to diverge.
"People with paranoia were particularly bad at detecting which dot was being chased," said Santiago Castiello , lead author of the study and a postdoctoral researcher in Corlett's lab. "And people with high teleology were particularly bad at detecting which dot was doing the chasing."
That these two types of beliefs differed in this way highlights that they are distinct and may have implications for diagnosis or treatment, said the researchers. The connection to vision may also shift thinking around how the brain gives rise to psychotic symptoms.
"Very few people with congenital blindness develop schizophrenia," said Castiello. "Finding these social hallucinations in vision makes me wonder if schizophrenia is something that develops through errors in how people sample the visual world."
While there are no immediate therapeutic implications from these findings, deeper understanding of these beliefs could aid in pharmacological treatment development and risk assessment.
"One thing we're thinking about now is whether we can find eye tests that predict someone's risk for psychosis," said Corlett. "Maybe there is some very quick perceptual task that can identify when someone might need to talk to a clinician."
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