Social influences on the amount of food eaten by Norway rats

A naive observer Norway rat offered a choice between two foods, after it in teracts with a demonstrator rat fed one of those foods, increases its prefe rence for whichever food the demonstrator rat ate. It is not known whether interaction with a demonstrator rat would also increase the amount that an observer rat would eat if it were given access only to the food the demonst rator had eaten. In this study, each observer rat interacted with a demonst rator rat fed a food, either familiar or unfamiliar to the observer, and th e observer was then offered a weighed sample of the food that the demonstra tor had eaten. It was found that, during the first hour of testing, observe r rats that had interacted with demonstrators fed an unfamiliar food, incre ased their intake of that food roughly four-fold. Observer rats that intera cted with demonstrator rats fed a familiar food however, did not increase t heir food intake. Socially enhanced intake of unfamiliar food was seen only during the first hour that observers had access to food and was compensate d for during the next 23 h of feeding. This short-term increase in observer intake of unfamiliar foods appeared to result from socially-induced motiva tion to ingest unfamiliar foods rather than from socially-induced reduction in neophobia. (C) 2000 Academic Press.