Figure 3.

Mean response rate and causality judgments for control (CTL) group and obsessive-compulsive disorder (OCD) group. (A) Mean response rate by contingency (ΔP). Both groups responded more for higher contingencies. However, patients with OCD showed reduced sensitivity to instrumental contingency. (B) Subjective judgments of causality increased as a direct function of response-outcome contingency in both groups. Data are presented in ascending order of programmed contingency, but contingencies were experienced by each subject in a semirandomized order. Error bar indicates Fisher’s least significant difference to facilitate post hoc comparisons (error bars are ± 0.5 least significant difference). However, in the context of mixed designs, as in this case, this error bar can be used only for within-subject comparisons. The difference between OCD and CTL groups in mean causality judgments at ΔP = −0.6 was not significant. However, CTL subjects, but not patients with OCD, subjectively detected a difference between neighboring levels of negative programmed contingency between ΔP = −0.3 and ΔP = −0.6). (C) Response rate as a function of causality judgment by group. The two populations differentially employed action-outcome knowledge to guide their behavior. Points and error bars (SEMs) show values clustered by programmed contingency. As described in the main text, data were collapsed across blocks having equal contingencies (ΔP = −0.6, block 6; ΔP = −0.3, block 5, block 9; ΔP = 0.0, block 2, block 3, block 4, block 8, block 12; ΔP = 0.3, block 7, block 11; ΔP = 0.6, block 1, block 10. See Table 2 for naming of the blocks). Programmed contingency refers to the a priori experimentally programmed contingency resulting from the a priori programmed conditional probabilities. *p < .05, within-group comparison; ^##p < .01, interaction; ^#p < .05, group × quadratic causality judgment interaction. n.s., not significant.