Of note, elevated SCRs and greater US expectancy ratings to the CS+E during early extinction learning were comparable to SCRs and US expectancy ratings to the CS+E during late fear acquisition in both drug groups [SCR: THC: t(13) = 0.44, p = 0.67; PBO: t(14) = 0.07, p = 0.94; US Expectancy: THC: t(13) = −0.41, p = 0.69; PBO: t(14) = 0.97, p = 0.35], supporting successful acquisition and next day retention of conditioned fear. In addition, there were no significant differences in SCRs to the CS+E and CS− between the THC and PBO groups within or between early and late extinction, as evidence by the absence of a significant main effect of drug [SCR: F(1,27) = 0.04, p = 0.85; US Expectancy: F(1,27) = 0.34, p = 0.57], drug by stimulus interaction [SCR: F(1,27) = 2.15, p = 0.15; US Expectancy: F(1,27) = 0.07, p = 0.80], drug by time interaction [SCR: F(1,27) = 0.07, p = 0.80; US Expectancy: F(1,27) = 0.03, p = 0.85], and drug by stimulus by time interaction [SCR: F(1,27) = 1.44, p = 0.24; US Expectancy: F(1,27) = 1.80, p = 0.19].
