Retrieval of inedible objects by Norway rats after habituation of gnawing: resistance to satiation?

Retrieval of wooden blocks by Norway rats was tested after continuous exposure to these objects sufficient to reduce gnawing. In two experiments rats were first allowed to retrieve during restricted daily trials. Then they were exposed to blocks in their home cages, and at some point during exposure they were retested in the retrieval situation. In Experiment 1, further retrieval tests were given beginning the day after blocks were introduced in the cages. In Experiment 2, rats were exposed to blocks for 100 days before they were retested for retrieval. In both experiments, amount of retrieval was minimally affected by exposure, although gnawing was significantly depressed. This contrasts with earlier work, which showed that habituation of gnawing in the cage was followed by a significant decline in retrieval. The major qualitative difference between this and past work was that rats in the present experiments were allowed to retrieve the blocks before continuous exposure to them. The author concluded that retrieval experience may lead to persistence of retrieval despite a decline in incentive value of the objects retrieved, indicated by the decline in gnawing, and he discusses relations to other demonstrations of persistence in the absence of original motivational conditions-in particular, "resistance to satiation" effects.