At the beginning of each session participants were told that they may or may not hear a loud noise burst and were instructed to pay attention to the computer screen and try to figure out the relationship between the colored squares and the noise burst. During each presentation of the colored square stimuli, participants were asked to rate their expectancy that the US would occur on a 5-point scale (“Will you hear a loud noise burst?”: 1 = Definitely not; 3 = Unsure; 5 = Definitely). US expectancy was scored as the first response within 3 sec of CS onset (adapted from (Dunsmoor et al., 2008)). Conditioned fear was indexed by changes in skin conductance responses (SCRs) for each CS trial. Electrodes and headphones remained in place during all sessions (removed only during breaks).
