Fig. 1.

Experimental design. The experiment was divided into different stages. Within each stage, all CSs were presented eight times each in a pseudorandomized order. During acquisition, two angry faces (CS + s) were repeatedly paired with a mild electric shock (US) given to the participants’ wrist (six reinforced presentations/CS). The third angry face (CS−) was never paired with the shock. During extinction, participants watched a video depicting an individual (the demonstrator) acting calmly when exposed to non-reinforced presentations of the CS− and to one of the previously reinforced CS + s (CS + _{vic safety}), but received shocks on the presentations of the other CS+ (CS + _{vic reinf}; six reinforced presentations). The demonstrator reacted to the shocks by twitching the arm and blinking. Critically, the participants did not receive any shocks during this stage. Finally, participants were then re-exposed to all three CSs after receiving three reminder shocks during the reinstatement test.