Silence resulting from the cessation of movement signals danger

been conditioned (conditioned demonstrator, CD). As previous reports showed that prior experience with foot-shocks is necessary for the ability to respond to the distress of the demonstrator [6,8], experienced observer (EO) rats received unsignaled footshocks on the day prior to the social interaction. We measured the time that demonstrator and observer rats spent freezing, a robust fear response [4]. As previously shown Experienced (Figure 1B), but not Naive (Supplemental Figure S1A in the Supplemental Information available on-line with this Silence resulting from the cessation of movement signals danger