Psychophysical methods for study of sensory-motor behavior using a food-carrying (hoarding) task in rodents

Rodents (rat, mouse, gerbil) display species-typical food-handling movements that are dependent upon features of the food they are given. They swallow small pieces of food directly, eat medium-sized pieces from their forepaws, and carry (hoard) large pieces of food to refugees for consumption or storage. Both food size and anticipated eating time influence the occurrence of a given movement. Response speeds are also influenced by food size. The latency to initiate food-carrying and travel-speed during food-carrying are inversely related to the size of food, while the latency to return to the food source for more food is directly related to the amount of food just eaten. Using menu-driven computer programs, event relays and photocells, and videorecording methods, the food handling movements can be both monitored and quantified. Use of the method is illustrated by showing how manipulations such as familiarity with the environment, environmental lighting, food pellet size and peripheral and central processes influence movements and response speeds. The procedure provides a useful way to study sensorimotor processes, motivation and reinforcement processes, and memory and cognitive processes used in foraging.