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Normal and abnormal reasoning in people with delusions
R E Dudley1, C H John, A W Young
1Department of Psychology, University of Durham, UK.
The British Journal of Clinical Psychology
|May 1, 1997
Summary
Individuals experiencing delusions exhibit a data-gathering bias, seeking less information before decisions. This "jump to conclusions" tendency, not an reasoning deficit, impacts information processing in delusions.
Area of Science:
- Cognitive Psychology
- Psychiatry
- Neuroscience
Background:
- Individuals with delusions often request less information before making decisions, even on unrelated topics.
- Previous research suggests this may indicate a deficit in reasoning or a specific bias in data gathering.
Purpose of the Study:
- To investigate whether delusions are associated with an absolute reasoning deficit or a data-gathering bias.
- To differentiate between a general impairment in reasoning and a specific tendency to seek less information.
Main Methods:
- Experiment 1: Compared reasoning in people with delusions, depression, and normal controls using a predetermined coin-spinning task.
- Experiment 2: Assessed decision-making under conditions where participants could control the amount of evidence (bead jar task) versus when evidence was predetermined.
Main Results:
- In Experiment 1 (predetermined evidence), all groups reasoned similarly.
- In Experiment 2, people with delusions gathered less evidence when free to choose, but not when evidence was fixed.
- This data-gathering bias, termed "jump to conclusions," was observed even with less distinct ratios and was not due to impulsivity or memory deficits.
Conclusions:
- People with delusions demonstrate a specific data-gathering bias, not a general deficit in reasoning.
- The findings highlight a tendency to make decisions with insufficient evidence in individuals with delusions.