Safety behaviours preserve threat beliefs: Protection from extinction of human fear conditioning by an avoidance response.

A laboratory autonomic conditioning procedure was used to establish fear conditioning in human participants by pairing neutral stimuli with electric shock. Participants were also trained to make a button-press response to avoid shock. A target fear stimulus was then extinguished by presenting it without shock. The experimental group was given the opportunity to make the avoidance response during extinction whereas the control group was not. When the fear stimulus was tested without the response available, the control group showed normal extinction of both shock expectancy ratings and skin conductance responses, but the experimental group showed "protection from extinction": they continued to give high expectancy ratings and strong skin conductance responses. We interpret this effect as analogous to the role of within-situation safety behaviours in preserving threat beliefs during exposure therapy for anxiety disorders. The results support a cognitive account of learning and anxiety. The procedure provides a potential laboratory model for further examination of the cognitive and neural mechanisms underlying anxiety and its reduction.

Forward blocking in human learning sometimes reflects the failure to encode a cue-outcome relationship.

In two "allergist" causal judgement experiments, participants were trained with a blocking design (A+|AB+). The procedure allowed different food cues to be paired with different fictitious allergic reactions. On test, participants were asked to rate the causal efficacy of the target cues and to recall the particular allergic reaction (outcome) that had followed each cue during training. Forward blocking was observed on the causal judgement measure and on the outcome recall measure in both Experiment 1 and Experiment 2. A backward blocking contingency was also trained in Experiment 2 (AB+|A+). Backward blocking was not observed either on the causal judgement or on the outcome recall measure. The evidence from the recall measure suggests that forward blocking in this task results from a failure to encode the B-outcome relationship during training. Associative and nonassociative mechanisms of forward blocking are discussed.