Figure 1.

Overview of experiment. (a) Learning phase. Demonstrator watched two images, one that terminated with an uncomfortable electrical shock during 4 of 6 presentations (CS+) and another that never terminated with a shock (CS−). Each CS presentation lasted 6 s and inter-trial interval (ITI) varied between 10 and 16 s. Valence (CS+/−) of the first image presented was randomly varied. While the demonstrator watched the CS presentations and received shocks, the Observer watched both the demonstrator and the CS’s. The Observer was instructed to learn the shock contingency. The observer received no shocks during the learning phase. Electrodermal activity was continuously recorded from both the demonstrator and observer. (b) Testing phase. Immediately following the learning phase, the Observer was repeatedly shown both CS’s again, instructed that they would receive shocks to the same image as the demonstrator had received shocks to. Importantly, only the 7th, final presentation of the CS+ terminated with shock, to not interfere with the measurement of the vicariously acquired threat response. Greater SCR to the CS+ compared to the CS− in the Observer, in this phase, indicates successful threat learning. (c) Expression of learning in the testing phase. Average trial-by-trial data from testing phase showing average skin conductance responses to the CS+ (dark circles) and to the CS− (light circles) for the Observer. Error bars are 95% confidence intervals. (Online version in colour.)