An ANOVA of SCR during fear acquisition revealed a significant main effect of stimulus [F(1,27) = 16.12, p < 0.001], with greater SCR responses to the CS+ [THC = 0.38 ± 0.08; PBO = 0.27 ± 0.08] than to the CS− [THC = 0.10 ± 0.07; PBO = 0.18 ± 0.06] during the last trial of fear acquisition. There were no significant differences in SCR during fear acquisition between participants assigned to the THC and PBO groups, as evidence by the absence of a significant main effect of drug [F(1,27) = 0.05, p = 0.82] or drug by stimulus interaction [F(1,27) = 4.11, p = 0.53]. Similarly, participants rated the US as more likely to occur during the CS+ [THC = 3.39 ± 0.20; PBO = 3.40 ± 0.21] than the CS− [THC = 1.29 ± 0.19; PBO = 1.47 ± 0.24] during the last trial of fear acquisition [main effect of stimulus [F(1,27) = 80.76, p < 0.001]. There were no significant differences in US expectancy ratings during fear acquisition between participants assigned to the THC and PBO groups
