Ontogeny of persistence: immediate and long-term persistence in rats varying in training age between 17 and 65 days

In Experiment 1, six age groups of rats were trained to run an alley for either partial (PRF) or continuous reinforcement (CRF). Training was during a 2-day period starting at six different ages, and extinction was initiated about 12 hr later. There was a clear partial reinforcement extinction effect (PREE) at all ages and, particularly after PRF training, an inverse relationship between resistance to extinction and age. In Experiment 2, retention and durability of persistence as well as immediate persistence were tested following acquisition at three different ages. The immediate extinction tests confirmed the results of Experiment 1. In the delayed extinction tests, greater resistance to extinction following PRF than following CRF was found in all age groups after both the retention and durability manipulations. In neither test was there an effect of age in original acquisition on the magnitude of adult persistence. These experiments confirm earlier findings of remarkable persistence in rats trained and tested at weanling age, show that the persistence is even greater in pre-weanlings, and show that it is retained into young adulthood.