[Methods for grading the strength of passive conditioned avoidance reaction]

Three methods for obtaining passive avoidance conditioned responses of different strength are described. The first method consists of delayed reinforcement, constituted by a foot-shock, in the conditioning trial. The second method corresponds to the "detention" procedure, through which the animal is kept in one part of the apparatus for some time, after the conditioning trial. The third method consists of using foot-shocks of different strength in the conditioning trial. This method, however, is not advisable in most cases, since it produces strong differences in the subjects' level of arousal after conditioning and therefore a different reactivity to the various treatments.