Video: Yoked-shock and No-shock Comparison
Compare the open field behavior of a “yoked” rat (left) that is shocked at random locations in the identical shock time series as a rat that was performing active place avoidance (not shown) and an "untrained” rat (right) that is merely exploring the rotating arena and has never been shocked. Can you tell the difference? It doesn’t look like contextual/threat fear conditioning as many have asserted and we can’t measure a difference in spatial behavior or corticosterone levels. Receiving these shocks is no more stressful than exploring a familiar space and is certainly less stressful than a water maze experience.