Increased generalisation in trait anxiety is driven by value transfer, not reduced perceptual discrimination

Anxiety has been linked to increased generalisation of threat expectations to stimuli that are perceptually similar. Such generalisation can arise either from a failure to distinguish between threatening and non-threatening stimuli (perceptual mechanism) or from the transfer of learned values between stimuli (value-based mechanism). Despite important implications for treatment, how these two mechanisms contribute to generalisation, and whether they are differentially impacted by anxiety remains unclear. Here, we combine a set of novel experimental and computational approaches to dissociate perceptual and value-based contributions to generalisation. Participants (N = 140) first underwent an extensive titration procedure that resulted in personalised stimulus spaces matched in perceived similarity across participants. These stimuli were then used in aversive conditioning and generalisation tasks while we varied outcome probability and discriminability. Using computational modelling, we show that some participants generalise due to a perceptual mechanism, while others due to value-based mechanisms. Further, we show that trait anxiety is associated with stronger generalisation to stimuli that are most dissimilar from the conditioned stimulus and that this effect is driven by greater reliance on value transfer, rather than an inability to discriminate stimuli. These results generate key novel insights into the nature of generalisation and how trait anxiety impacts generalisation at the level of cognitive mechanisms.