Cognitive theories of delusion formation

Cognitive Models - Brain's Belief Glitches

• Two-Factor Model: Dominant theory. Delusions arise from:

  • Factor 1: An anomalous experience (e.g., strange sensory event, heightened perception).
  • Factor 2: Impaired reasoning that fails to reject the resulting bizarre explanation.

• Key Cognitive Biases (📌 Mnemonic: J.A.T.):

  • Jumping to Conclusions (JTC): Making firm judgments based on scant evidence.
  • Attributional Style: Externalizing blame for negative outcomes (common in persecutory type).
  • Theory of Mind (ToM) Deficit: Impaired ability to infer others' intentions.

⭐ The "Jumping to Conclusions" (JTC) bias is a classic finding; patients require significantly less data than controls to reach firm, often premature, conclusions.

Explanatory Models - One vs. Two-Factor Theories

• One-Factor (Bottom-Up) Theory:

  • A single deficit, an anomalous experience (e.g., strange perception), is sufficient to generate a delusion.
  • The delusion is a direct explanation for the experience.
  • Example: Loss of affective response to a face → Capgras belief ("imposter").

• Two-Factor (Hybrid) Theory:

  • Requires two cognitive deficits.
  • Factor 1 (Bottom-Up): An anomalous experience creates a bizarre hypothesis.
  • Factor 2 (Top-Down): Impaired belief evaluation prevents rejection of the irrational hypothesis.

⭐ High-Yield: Two-factor models explain why many with neurological abnormalities (Factor 1) don't develop delusions. Without a second deficit in reality-testing (Factor 2), they can dismiss strange experiences and do not form a fixed, false belief.

Cognitive Biases - The Mind's Usual Suspects

• Jumping to Conclusions (JTC): Most replicated finding. A tendency to form beliefs with minimal evidence.
  • Assessed via the "beads task" (probabilistic reasoning); patients make a choice with fewer draws.
• Attributional Biases:
  • Externalizing: Blaming external factors for negative outcomes.
  • Personalizing: Viewing neutral events as self-referential (e.g., "they are laughing at me").
• Confirmation Bias: Seeking information that confirms one's delusions while ignoring contradictory evidence.
• Theory of Mind (ToM) Deficits: Impaired ability to infer the mental states of others, leading to misinterpretation of social cues.

⭐ The JTC bias is considered a stable vulnerability marker for psychosis, not just a symptom of active delusions.

Neurocognitive Links - Dopamine's Aberrant Salience

• Core Idea: Dysregulated mesolimbic dopamine (DA) causes the brain to assign inappropriate significance ("salience") to neutral thoughts and external stimuli.
• This is a "bottom-up" neurochemical error.
• The cortex then creates a "top-down" cognitive narrative (the delusion) to make sense of this aberrant salience.

⭐ Antipsychotics (D2 antagonists) are thought to work by dampening this salience. The delusion may persist, but it feels less important and distressing to the patient.

High-Yield Points - ⚡ Biggest Takeaways

• Jumping to conclusions (JTC) bias is a core cognitive error, leading to firm beliefs based on minimal evidence.
• Patients often show externalizing attributional biases, blaming outside forces for negative events.
• Deficits in Theory of Mind (ToM) impair understanding of others' intentions, fueling persecutory beliefs.
• Anomalous perceptual experiences can act as the initial seed for a delusional belief system.
• The two-factor theory requires both an unusual experience and a cognitive bias to explain it.