Jaw-Sy Chen

Prolonged, unsignaled, inescapable shocks increase persistence in subsequent appetitive instrumental learning

In the first experiment, a prolonged period of intermittent, unsignaled shocks preceded appetitive runway acquisition, under either continuous (CRF) or partial reinforcement (PRF) and extinction. In the second experiment, the shock treatment came between CRF or PRF acquisition and extinction; and in the third experiment, the shocks intervened between appetitive CRF acquisition and shock-punishment extinction. The main finding was that compared with an unshocked control, shock facilitated acquisition in Experiment 1, and led to increased resistance to extinction and/or punishment in all experiments. In Experiment 1, the shock effect in appetitive extinction was seen mainly in the CRF group; in Experiment 2, the effect was to increase persistence in both the CRF and PRF groups; and in Experiment 3, shock treatment produced stronger resistance to punished extinction. The discussion is in terms of habituation and a general theory of persistence, and the concept of helplessness.

Ontogeny of persistence: Immediate extinction effects in preweanling and weanling rats

In Experiment I rats were trained for 21÷2 days under partial (PRF) or continuous reinforcement (CRF) conditions starting at 18, 22, 28, or 36 days of age and were then subjected to immediate extinction. At all ages there was a strong partial reinforcement extinction effect (PREE), and absolute size of PREE was greatest in the youngest rats. Rate of extinction increased as a function of age following both CRF and PRF. In Experiment II the youngest and oldest age groups of Experiment I were run under the two reward conditions of Experiment I and in a third condition, PRF with number of rewards rather than trials equated to CRF (PRF-R). The PRF-R and PRF groups were not different in extinction, and both were more persistent than CRF. The youngest rats were again more persistent than the oldest, particularly after PRF training. In Experiment III it was shown that the well-known paradoxical effect, greater reward in CRF acquisition leads to faster extinction, operates in our youngest and oldest animals, but is more pronounced in the oldest. The results are discussed in terms of whether they require different explanations than those often applied to extinction data from adult rats.

The partial reinforcement acquisition effect in preweanling and juvenile rats

Evidence of the partial reinforcement acquisition effect (PRAE), faster running after partial reinforcement than after continuous reinforcement in the start and run segments coupled with slower running in the goal segment of a straight-alley runway, was obtained in preweanling (18-20 days of age) and young adult (52-54 days of age) rats. While present at both ages, the PRAE appears to increase with age. The results are discussed in relation to previous studies of this and other paradoxical reinforcement effects.

Durable partial reinforcement effect and social dominance in two inbred mouse strains

The partial reinforcement effect (PRE) was investigated in C57BL/10J (C57) and DBA/2J (DBA) inbred mice in a straight runway. The PRE was obtained in both strains and was sustained through extended extinction and continuously reinforced (CRF) reacquisition. Two weeks after the completion of the second runway extinction test, PRF and CRF Ss of each strain were pitched against each other in a tube dominance test. PRF Ss won a significantly greater number of the contests.

The effects of prolonged thwarting on instfumental response extinction

To study the effects of prolonged frustration on extinction of a subsequently learned running response, one group of rats (CF) were subjected to a treatment in their individual home cages in which food was visible but unattainable for extended periods of time. A control group (NF) remained untreated. All Ss were then trained in a runway under conditions of continuous reinforcement followed by extinction. Both groups were then retrained in the runway with continuous reinforcement followed by a second extinction. In the second extinction, visible but unattainable food, rather than nonreward, was employed. Ss from Group CF extinguished faster and retraced more than did those from Group NF in the first extinction; in the second extinction, the differences were in the same direction but were not significant.