Figure 2.

Averaged perceived risk of shock (0 = no risk, 1 = some risk, 2 = high risk) plotted across conditioned danger-cues (CS+), generalization stimuli (GS₃, GS₂, GS₁), and conditioned safety-cues [ring-shaped (oCS−) and V-shaped (vCS−)] for each group. This reflects data for the current sample, which includes three fewer subjects than the prior analysis (Kaczkurkin et al., 2017) due to more stringent motion requirements. Main effects of stimulus-type were present for each group (ps < 0.0001). Dotted lines indicate hypothetical linear decreases in responding from CS+ to oCS− with which to visualize the deviation of gradients from linearity in each group. Such deviations reflect a significantly stronger linear component in the generalization-gradient of PTSD and SubPTSD relative to TC (ps < 0.05), indicating more gradual, linear declines indicative of overgeneralization in PTSD and SubPTSD. To identify the point on the continuum-of-similarity at which perceived risk ceased to generalize for each group, planned comparisons contrasting oCS− against CS+ and GS₃, GS₂, and GS₁ were computed. Black data points signify stimulus types eliciting increased risk ratings relative to oCS− after applying Hochberg’s adjustment for multiple tests (Hochberg, 1988). In TC, perceived risk was elevated from oCS− to CS+ (p < 0.001) and GS₃ (p < 0.001). By contrast, in PTSD and SubPTSD, perceived risk was elevated from oCS− to CS+ (all ps < 0.001), GS₃ (all ps < 0.001), GS₂ (all ps < 0.001), and GS₁ (all ps < 0.016). Thus, while TC generalized perceived risk only to one degree of differentiation from CS+ (i.e. GS₃), those in PTSD and SubPTSD groups generalized to three degrees of differentiation (i.e. GS₃–GS₁).