Individual threat-relevance accelerates belief-updating in conditioned hallucinations.

Threat-related learning is implicated in psychopathological hallucinations; however, its role in experimentally-induced hallucinations remains unclear. Here, we investigated how threat-relevant stimuli (spiders vs. flowers) influence conditioned hallucinations (i.e., illusory auditory tones triggered by learned associations with images). We found that, for conditioning with spiders (but not flowers), higher spider-phobia was related to time-dependent variations in conditioned hallucinations: increasing in early phases (where spiders reliably predicted tones) and decreasing in later phases (as this predictive relationship weakened). These tendencies were related to accelerated belief-updating in a hierarchical Gaussian filter model and shifts in participants' internal criterion within a signal detection framework. Additionally, trait anxiety and hallucination-proneness were inversely related to conditioned hallucinations and reliance on prior beliefs, but did not significantly vary according to image condition. Unlike the theorized role of threat in developing rigid priors and clinical hallucinations, our findings indicate that individual threat-relevance sensitises hallucination-related beliefs to shifting stimulus contingencies.