Psychophysiology
During acquisition, the SCR showed a significant Stimulus x Time interaction, F (1,255) = 13.99, p < .001,R 2 = .114, and a significant Stimulus x Group interaction, F (2,255) = 3.71, p = .026,R 2 = .024, but the Stimulus x Group x Time interaction was not significant, F (2,255) = 0.23, p = .792, R 2 = .002. Follow-up analyses showed that the difference between CS+ and CS- was larger in group HU compared to LU, bGroup(HU-LU)*Stimulus = -0.02 , SE = 0.01,t (261.00) = 2.48, p = .014 but there was no difference between groups HU-MU, bGroup(HU-MU)*Stimulus = -0.007 , SE = 0.01, t (261.00) = 0.67, p = .501 or LU-MU,bGroup(LU-MU)*Stimulus = 0.02 , SE = 0.01,t (261.00) = 1.87, p = .062 (Bonferroni correction α < .017). Furthermore, as shown in Figure 3, averaged across groups, participants showed increased differential SCR responding in Acq1 compared to Acq2, bTime*Stimulus = -0.03 , SE = 0.01, t (261.00) = 3.77, p < .001.
For ssVEPs in acquisition, there was no significant main effect of Stimulus or Group (all p values >.331) indicating that participants’ visuocortical engagement was similar for the two stimuli across the three groups, see Table 3 for means and standard deviations per test stimulus. There was a significant main effect for Time, F (1,255) = 8.30, p = .004,R 2 = .033 with overall stronger responses in Acq1 (M = 1.19, SD = 1.40) than Acq2 (M = 1.03,SD = 1.24). No interaction effects were found (all pvalues >.393). Consequently, there was no difference in visuocortical engagement for either of the two faces and no group differences (HU: CS+: M = 1.29, SD = 1.34, CS-:M = 1.19, SD = 1.06, MU: CS+: M = 0.79, SD = 0.94, CS-: M = 0.84, SD = 1.00, LU: CS+: M = 1.30, SD = 1.76, CS-: M = 1.20, SD = 1.65) but there was more visuocortical engagement to both faces during Acq1 than Acq2.