Pecking and feeding in chicks

Abstract

Pecking is not controlled by nutritional state in a newly hatched chick, but by 3 days posthatch it normally is. This paper tests the hypothesis that first a chick must learn that pecking leads to ingestion; then, other (nonlearned) processes are automatically responsible for differential pecking rates to nutritive and nonnutritive items. The first experiment shows that experience pecking and ingesting sawdust is sufficient for differential pecking to develop. The second experiment shows that swallowing without pecking (using a force-feeding technique) does not lead to differential pecking. The third experiment shows that pecking without swallowing (using sand glued down to the floor) also does not lead to differential pecking. Finally, the last experiment shows that food deprivation affects pecking rate only after pecking and ingestion have been associated. These results support the above hypothesis that pecking followed by ingestion leads to the “attachment” of the pecking response to the feeding system. Motivational independence of pecking and the hunger system, the association of pecking with ingestion, and the development of behavior systems are discussed. It is concluded that the function of a behavior may not be related to its causes.