Effects of social and asocial learning on longevity of food-preference traditions

The influence of both social and asocial factors on the stability of a socially learned tradition of food preference was explored in colonies of domesticated Norway rats, Rattus norvegicusWe trained members of 'founding colonies' of rats to avoid eating a distinctively flavoured food and then introduced them into enclosures where they were offered a choice between the food they had learned to avoid and a familiar, safe food. We then monitored the food preferences of these colonies while we gradually replaced founding members with naive subjects. Traditions of food preference were more stable across generations of replacements: (1) in colonies that had food available 2 h/day than in colonies that had food available 24 h/day (experiment 1), (2) when replacement subjects each resided in their respective colonies for 2 days rather than for 4 days before themselves being replaced (experiments 2 and 3) and (3) when founding members of colonies had learned to avoid a relatively palatable diet (experiment 4). The results of the first four experiments were consistent with the view that opportunities to learn asocially to eat a food other than that preferred by one's fellows reduced the stability of a food preference as it was transmitted across generations. We also found that introducing a naive individual into a tradition-bearing colony reduced its rate of acquiring a food preference other than that of the colony it joined (experiment 5). The interactive effects of social and asocial learning on the stability of food preference traditions in Norway rats was discussed.