| Abstract: | In the first of two experiments, running-wheel activity and unsignaled (Sidman) avoidance were studied in gerbils and albino rats. All gerbils ran at higher rates than any of the four rats studied. Under the avoidance procedure, four rats developed effective responding; the other two performed much less successfully. While avoidance developed more slowly in the gerbils, all showed asymptotic performance as effective as the four superior rats. The rats showed a consistent warm-up effect, receiving 60% to 80% of the total shocks in the initial third of the session. The gerbils displayed no warm-up, with shocks being evenly distributed over the session. Warm-up in the rats was not related to either response rate or to how effectively the animal was avoiding. When shock was removed, extinction occurred more rapidly in the rats than the gerbils. In the second experiment, which involved two-way shuttle avoidance, gerbils and albino mice quickly acquired the response. All animals met a criterion of 90% avoidance over 80 trials. |
