Inducing Acute Anxiety with Unpredictable Shocks

Acute anxiety was induced by unpredictable electrical shocks delivered using a Digitimer DS7A Constant Current Stimulator (Digitimer Ltd., Welwyn Garden City, UK), with two electrodes secured to the wrist (as per Robinson et al.10 (link)). Each participant completed a shock thresholding procedure, consisting of a few (usually 2 to 5) electrical shocks of increasing intensity, to reach a level of ‘painful but tolerable’ i.e. 4 on a scale from 1 (no sensation) to 5 (painful and not tolerable).
Threat and safe blocks were indicated by an orange screen with ‘YOU ARE NOW AT RISK OF SHOCK’ or a blue screen with ‘YOU ARE NOW SAFE FROM SHOCK’ displayed for 3 seconds at the start of each block (Fig. 1B), and throughout the block by an orange or blue border, indicating threat or safe, respectively. A total of 6 shocks was delivered across the 9 threat blocks (see asterisks in Fig. 1A for approximate position of shock delivery throughout the task). On each of these six shock trials, the shock was either administered during the first or second fixation cross. Participants were informed that shocks would be unpredictable and independent of performance on the gambling and memory tasks.