Level of Current and Time between Sessions as Factors in “Adaptation” to Shock

Three groups of 16 rats were exposed to no shock, 200 microamperes, or 400 microamperes, respectively, for 50 min. The next day, half of each group were trained to press a bar to turn off a 200 μa shock and half were trained to turn off a 400 μa shock. The higher the current during the first (exposure) session, the lower and more variable was the rate of pressing during the second (training) session. The higher the current during training, the higher and less variable was the rate of pressing. The persistence of the effects of prior exposure after 24 hr. suggests that some kind of learned behavior is involved.