Manipulating reinforcement probability changes the temporal overestimation of anticipated aversive stimuli.

The interval timing can be distorted by emotions. Previous studies indicated that anticipated fear stimuli can lead to temporal overestimation, similar to the effects observed from direct exposure to fear stimuli. However, this time distortion may not always manifest when anticipated. This study aimed to systematically examine the effect of the reinforcement probability of anticipated fear stimuli on time perception in predictable emotional scenarios. The experiment established 100% fear conditioning by associating a conditioned stimulus (CS+) with an aversive unconditioned stimulus (US), electrical stimulation. Participants completed a temporal bisection task under different cues (threat CS+ and safe CS-) expectations. Participants were explicitly informed that an aversive electrical stimulus would always follow the threat cues (CS+) with 100% probability, though in reality, different blocks presented the threat cue with probability manipulation of 50 and 100%. Results showed that only in the 50% reinforcement probability, participants overestimated the duration when anticipating aversive electrical stimulation, while no significant differences were observed in the 100% reinforcement probability. Additionally, the effect of anxiety on temporal judgment failed to capture the overall trend as fixed effects but only contributed to the individual variations as random effects. The findings suggest that the anticipated aversive electrical stimulation may lead to temporal overestimation. Furthermore, the results indicate that a reliable approach for manipulating the effect of anticipated aversive electrical stimulation on temporal overestimation is to establish 100% fear conditioning and use a reinforcement probability like 50%.