Psychophysiology
In the generalization phase, the analysis for SCR returned a significant
difference between the stimuli, F (5,424.03) = 22.93, p< .001, R 2 = .213 but neither a
difference between the groups, F (2,85.00) = 1.20, p =
.307, R 2 = .027, nor a significant Stimulus x
Group interaction, F (10, 424.03) = 0.91, p = .528,R 2 = .021. Simple contrast models demonstrated
that participants’ SCR response to CS- differed significantly as
compared to CS+, b(CS-, CS+) = 0.03, SE = 0.004,t (434.00) = 8.24, p < .001, GS1,b(CS-, GS1) = 0.02, SE = 0.004, t (434.00)
= 6.60, p < .001, GS2, b(CS-,
GS2) = 0.01, SE = 0.004, t (434.00) = 2.89, p = .004, but
did not differ to GS3, b(CS-, GS3) = 0.00, SE =
0.004, t (434.00) = 1.07, p = .287, and GS4,b(CS-, GS4) = 0.00, SE = 0.004, t (434.00)
= 0.38, p = .706 (Bonferroni correction α < .010).
Trend analysis revealed both a significant Linear, F (1,437.00) =
108.72, p < .001 and a Quadratic trend across stimuli
and groups, F (1,433.04) = 7.98, p = .005. The linearity of
the overall SCR generalization gradient was characterized by a monotonic
decrease from CS+ to CS-; while the curvature of the gradient was
characterized by a strong generalized responding from CS+ to GS1 and
GS2.
For ssVEPs, the main effect of Stimulus just failed to reach the
significance level, F (5, 425) = 2.15, p = .059,R 2 = .025, and there was no main effect of
Group, F (2,85) = 1.43, p = .244,R 2 = .033, or Stimulus x Group interaction,F (10, 425) = 1.12, p = .341, R 2 =
.026, indicating that participants’ visuocortical engagement was almost
similar for the six stimuli in the three groups. We exploratorily
followed the nearly significant main effect of Stimulus since it was one
of our main hypotheses. Simple contrast models indicated that only GS2
differed significantly from CS-, b(CS-, GS2) =0.10, SE = 0.04, t (435.00) = 2.34, p = .019, but it did
not survive Bonferroni correction (α < .010). All other
stimuli showed no significant differences from CS- (CS+:b(CS-, CS+) = 0.03, SE = 0.04, t (435.00) =
0.77, p = .441 , GS1: b(CS-, GS1) = 0.04,
SE = 0.04, t (435.00) = 0.98, p = .326, GS3:b(CS-, GS3) = - 0.01, SE = 0.04, t (435.00)
= 0.21, p = .838, GS4: b(CS-, GS4) =
- 0.02, SE = 0.04, t (435.00) = 0.50, p = .616. Further
trend analyses returned neither a Linear, F (1, 438) = 3.34,p = .068 nor a Quadratic trend across the test stimuli,F (1, 438) = 0.63, p = .428. Mean signal topographies for
ssVEPs in generalization can be found in Figure 4.