Figure 2.

Detailed trial timing schema. The drawing of a lightning bolt represents the pain-US, a drawing of a musical note represents the startle probe presentation, and the “+” represents the starting signal, “(1–8)” refers to the presentation of a number between 1 and 8 representing the quadrant in which the participants have to move. (A) In the predictable group, during the acquisition phase, pain-USs are delivered in 75% of the trials after the CS+ movements, but not after the CS- movements. On each trial only one startle probe was presented: in the predictable group, this could be during the CS movement or during the pre-CS ITI or post-CS ITI. (B) In the unpredictable group pain-USs are delivered at the same rate either during the pre- or post-CS intertrial interval (ITI) and startle probes also could be presented during the CS movement or during the ITI – when the pain-US was presented in the pre-CS ITI, probes were presented in the post-CS ITI, and if the pain-US was presented during the post-CS ITI, probes were delivered during the pre-CS ITI. In both groups, no pain-USs were delivered during the generalization phase.