Sidman avoidance in the fish.

Goldfish trained in a shuttle box under conditions in which changing compartments postponed shock for 20 sec showed a substantial, negatively accelerated increase in rate of crossing. That the avoidance-contingency was responsible for the change in behavior is suggested by the fact that no significant increase in rate of crossing appeared in control animals which were paired with the experimentals and shocked whenever the experimental animals were shocked; there is some evidence, indeed, that the control animals were handicapped in their subsequent adjustment to the avoidance condition. The introduction of a warning stimulus (light) in the last 5 sec of the response-shock interval decreased the rate of crossing in the first 15 sec and increased the rate of crossing in the last 5 sec. Reducing the shock-shock interval from 20 sec to 2.5 sec had no marked effect. The results are compared with those obtained in analogous experiments with higher animals.