Human fear conditioning depends on stimulus contingency instructions

Human fear conditioning is often seen as the result of a highly automatic process that is independent of higher cognitive functions and verbal instructions. However, cumulative research findings call this view into question. In the current preregistered study (N = 102), we investigated whether the number of participants who successfully show conditioned fear acquisition depends on the instructions given to them before the fear conditioning phase. Particularly, one third of the participants were instructed about the precise contingency between the conditioned stimulus (CS) and unconditioned stimulus (US). Another third was merely instructed that there would be a contingency. The last third did not get any instructions about the CS-US contingency. We found facilitated fear acquisition rate in the first and second group compared to the third group. Furthermore, contingency reversal instructions following the acquisition phase reversed both conditioned skin conductance and startle responses. These results highlight that researchers should systematically report the instructions given to participants in human fear conditioning studies.