This experiment examines whether the relational responses of pigeons are controlled by the relations between stimuli on a relative numerosity discrimination, using multiple-pair discrimination training. In the discrimination training, three birds discriminated two pairs of number stimuli (1-3, 5-7). For two birds, the responses to smaller arrays were reinforced, and for the remaining bird, the responses to larger arrays were reinforced. After the birds learned to discriminate numerosity stimuli, a test was conducted, in which four test pairs (1-5, 3-7, 2-6, 2-5 or 3-6) were presented. Three of the four test pairs were combinations of stimuli with the same reinforcement history (S+-S+, S--S-, novel-novel), and one test pair was a combination of a stimulus with S+ history and a novel stimulus. The results of the tests showed that all the birds mostly demonstrated relational responses. Although the possibility still remains that other factors might affect the responses of the birds, the results provided evidence that the performances of the birds are mainly controlled by the relations between stimuli.

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Previous studies have demonstrated that the thirst drive interferes with the hunger drive in an animal's performance of motivated behavior: water deprivation causes a reduction in food-reinforced instrumental performance of food-deprived rats. In other words, irrelevant thirst causes devaluation of the food reinforcer. Here, we examined whether this type of reinforcer devaluation effect would require the animal's consummatory contact with the reinforcer under the irrelevant drive (i.e., incentive learning). Three groups of food-deprived rats were trained to press a lever for food pellets. Next, two groups (HT-pel and HT-) were cumulatively deprived of water, whereas the other group was deprived of food alone (H-pel), and all animals received an extinction test on the lever. Thereafter, groups HT-pel and H-pel were allowed to consume pellets, and lever pressing was tested again in extinction for all animals. We found that the irrelevant thirst, by itself, did not affect instrumental performance. However, the animals exposed to pellets under irrelevant thirst (HT-pel) exhibited a reduction in instrumental performance, suggesting incentive learning's role in the reinforcer devaluation effect caused by the irrelevant drive state.

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Individual animals show consistent differences in their behavioral tendencies. Some individuals are generally bolder, shyer, or more aggressive than others. This phenomenon is termed as animal personality or behavioral syndrome, and it has been observed in a wide range of animal species. In this article, we review the personality concepts and methodologies that has been used in two major study fields on this topic, i.e. the animal personality psychology and the behavioral syndrome research. Then, we shed light on how we can understand consistency in individual behavioral tendencies and how we can describe individual differences in animal behavior, by focusing on the differences and similarities between two study fields. Finally, we emphasize the importance of evolutionary framework for an integrated understanding of personality in non-human animals.

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Long-lasting change of the synaptic efficacy of neurotransmission in the hippocampus is thought to be one of the physiological bases of memory. Acetylcholine, one of the neurotransmitters, is mainly released from the medial septum to the hippocampus. The activation of muscarinic acetylcholine receptors (mAChR) reportedly enhances hippocampal synaptic plasticity; however, the mechanism by which it does this remains unclear. We addressed the involvement of the inhibition of Kv7/M K⁺ channels, which are a target of mAChR modulation, during mAChR activation-induced enhancement of long-term potentiation (LTP) at rat hippocampal Schaffer collateral (SC)-CA1 synapses.

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