FIGURE 1.

Schematic illustration of the experimental procedure (A) and stimulus presentation (B). (A) A brief practice run and shock work-up procedure preceded the experiment. In the first experimental block (instantiation), participants were verbally instructed that one particular emotional facial expression signals threat-of-shock (e.g., happy) or safety (e.g., angry and neutral faces). The second experimental block (reversal), started with a verbal reversal instruction stating that now threat and safety contingencies are reversed. Now neutral faces cued shock threat in both experimental groups, and happy and angry faces signaled safety in Block 2. The order in which facial expressions cued threat (happy–neutral or angry–neutral) was tested in two groups of each N = 20. After each block, threat and safety cues were rated regarding valence, arousal, and perceived threat. (B) During the experimental blocks, happy, neutral and angry face pictures were presented (each 6 s) with a variable inter-trial interval (ITI, 10 to 15 s). In total, 24 pictures were presented together with an auditory startle probe (and six ITI startles), which were equally distributed across experimental conditions. No shocks were presented during the experiment. Example pictures are taken from the KDEF with permission (identifiers: af01has, am08nes, am10ans, and af20ans; see Lundqvist et al., 1998; http://kdef.se/home/aboutKDEF.html).