Likelihood thought–action fusion (TAF-L) refers to a cognitive bias in which individuals believe that the mere thought of a negative event increases its likelihood of occurring in reality. TAF-L is most commonly associated with obsessive–compulsive disorder (OCD) but is also present in depression, generalized anxiety disorder and psychosis. We induced TAF-L in individuals with high (High-OC, N = 23) and low (Low-OC, N = 24) levels of OC traits, and used low resolution electromagnetic tomography (LORETA) to localise the accompanying electrical brain activity patterns. The results showed greater TAF-L in the High-OC than in the Low-OC group ( p < .005), which was accompanied by significantly greater upper beta frequency (19–30 Hz) activity in the precuneus ( p < .05). Further, the precuneus activity was positively correlated with self-reported magnitude of TAF-L ( p < .01), suggesting a specific role of this region in this cognitive bias. Results are discussed with reference to self-referential processing and the default-mode network.