Illusory correlation, on-line probability estimates, and electrodermal responding in a (quasi)-conditioning paradigm.

Twenty normal subjects were exposed to two series of two different slides randomly paired with the occurrence or non-occurrence of shock. The first series started with a greater number of pairings of one slide with shock ("target slide") than the other to induce an illusory correlation (IC). Meanwhile, across all trials shock/slide contingency was equal for both slides. During the second series, a truly random sequence of slide-shock trials was used in order to examine whether IC was resistant to disconfirmational information. Subjects' contingency estimates were recorded a posteriori as well as on-line. In addition, electrodermal responding was recorded on a trial-by-trial basis. Data show that it is possible to induce an IC between a neutral stimulus and an aversive outcome by means of a conditioning-like procedure. Moreover, data strongly suggest that an IC can act in such a way as to maintain or enhance covariation bias as indexed by on-line probability estimates. Finally, data sustain the hypothesis that a covariation bias is associated with differential autonomic responding.