Object retrieval preferences of Norway rats: an evolutionary generalization of behavior.

Prior studies have shown that object retrieval (including food hoarding) by domestic rats can occur in the context of different motivations. The present experiments show that retrieval preferences related to two motivational systems, feeding and gnawing, are ordered by object features related to either or both systems. Object retrieval in this species is apparently guided by a generalized value system. The capacity to order alternatives across specific motivational systems has evident selective advantage and may reflect a general adaptive principle.