responses to the CS+E during extinction recall, as evidenced by significantly greater SCRs to the CS+E during extinction recall than during late extinction learning [Late Extinction learning: 0.13 ± 0.04 vs. Extinction Recall Test: 0.37 ± 0.11; t(14) = −2.45, p < 0.05], whereas THC during extinction learning prevented spontaneous recovery of conditioned fear responding to the CS+E [Late Extinction learning: 0.13 ± 0.05 vs. Extinction Recall Test: 0.22 ± 0.08; t(13) = −0.94, p = 0.37]. As expected the THC group reported low subjective US expectancy ratings to the CS+E during the extinction recall test [2.07 ± 0.35] that were not significantly different from late extinction learning [1.91 ± 0.33; t(13) = −1.80, p = 0.10], further suggesting good retention of extinction memory. Interestingly, the PBO group also reported low subjective US expectancy ratings to the CS+E during the extinction recall test [2.07 ± 0.32] that were no different from the THC group [t (27) = −0.48, p = 0.64] or from late extinction learning [1.90 ± 0.32; t(14) = −0.68, p = 0.51]. These results suggest that the PBO group was able to maintain subjective knowledge that the CS+E no longer predicted the occurrence of the US despite
