Fig. 4.

Experimental neurosis in the pig. The animal learned to distinguish between two tones, one for shock and one for food, which signaled to the animal that it could open the food-box (bottom left) and receive a piece of apple. They alternated the signal and stimulus, the tone for food now resulting in shock, and exerted unwelcome restraints such as shocking the pig when it touched the fence or the food box without the signal being given. This resulted in neurotic behavior whereby the animal would refuse the apple in the experimental room, even when freely given, and exhibited tantrums and extreme aggression—attacking the food-box, the pen, and even the experimenters. Image courtesy of Division of Rare and Manuscript Collections, Cornell University Library, HSL, Box 10