P. Marler* and H. S. Terrace** *The Rockefeller University Field Research Center Millbrook, NY 12545 **Dept. of Psychology, Columbia University New York, NY 10027, USA For the first half of this century, theories of animal conditioning were regarded as the most promising approach to the study of learning - both animal and human. For a variety of reasons, disillusionment with this point of view has become widespread during recent years. One prominent source of disenchantment with conditioning theory is a large body of ethological observations of both learned and unlearned natural behavior....