We have found that pigs learn to press a lever several times consecutively before consuming their reward under a continuous reinforcement (CRF) schedule of operant conditioning. The present study examined determinants of the magnitude of consecutive responses. In Experiment 1, the magnitude of consecutive responses was greater when the lever-feeder distance was far (385 cm) than when it was near (19 cm). This result supports the hypothesis that consecutive responding is a foraging strategy to reduce the traveling cost required for shuttling behavior between the lever and the food cup. In Experiment 2, the number of consecutive responses was gradually decreased and approached the target magnitude by selectively reinforcing a smaller number of consecutive responses. These findings suggest that pigs are sensitive to the relation between response cost and reward gain to some extent, and can adjust their behavior to a fine degree with salient feedback.

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Newts were trained under a massed-trial condition and then extinguished in a straight alleyway to assess the partial reinforcement extinction effect (PREE). There were four groups: one partial reinforcement group trained using a random schedule (RA), two partial groups for which reinforcement ratios were gradually increased (GI) or decreased (GD), and a continuous reinforcement group (CR). They showed significant acquisition and extinction effects. The CR group was the most resistant to extinction, with no significant difference among the other three. The results indicate a reverse PREE in newts, and suggest that their learning is controlled mainly by a simple Strengthening-Weakening mechanism.

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Twenty-nine Wistar rats were tested for their spontaneous wheel running activity in daily 1-h sessions first under a free-feeding condition for 7 days, next with body weights decreased to 85% of their free-feeding weights. In the free-feeding phase, the number of wheel turns did not increase over the phase. In the 85%-body-weight phase, the number of wheel turns increased over the phase. In contrast, the number of wheel turns per 3 minutes decreased from the start to the end of the session on day 1 and day 7 of both phases. And, the number of wheel turns in the 85%-body-weight phase was greater on day 7 than on day 1. Spontaneous wheel running can reinforce other operant responses and such self-reinforcing mechanisms could be more effective during the 85%-body-weight phase.

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Primates have evolved to allow placing their hands in front of their face, where precise three-dimensional structures could be analyzed through their unique binocular vision. Primate parietal cortex possesses neural mechanisms subsurving such elaborate shaping of hands under visual supervision, which should have in turn enabled higher primates to handle primitive tools. Such parietal multimodal integration may not be limited to interpretations of represented shapes and the meanings of spatial structures, but may also be extrapolated to higher intellectual functions in humans.

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