Pigeons and goldfish were trained in red-green discrimination in daily sessions, with the rewarded color changed every 2 days. Improvement in the performance of the pigeons could be traced to decrements in retention from each day to the next. The goldfish showed no improvement and no decrements in retention. The results suggest that progressive improvement in habit reversal is a product of proactive interference, and that the absence of improvement in the fish is due, not to the lack of some higher-order process which operates to produce improvement in higher vertebrates, but to a difference in learning-retention mechanisms.

No abstract

Groups of goldfish and African mouthbreeders trained under a variety of conditions gave no reliable evidence of progressive improvement in habit reversal.

No abstract

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.