Animal behavior in the irrelevant situation has been paid little attention in contrast to that in the relevant situation, i. e., typical conditioning researches. The present article reviewed the researches using the “dual-training paradigm” for investigating the animal behavior in the irrelevant situation which includes “learned irrelevance” and “learned helplessness” phenomena. To classify the researches, three criteria were applied; type of training (S-S^* or R-S^*), type of S^* (aversive or appetitive), and type of contingency (+, -, or 0). The classification made it clear the direction of investigation.

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Although taste aversion learning is regarded as a kind of Pavlovian conditioning, what is learned in this preparation seems to differ from other Pavlovian paradigms. For example, animals learn to shift the hedonic value of a target taste stimulus followed by toxin in the aversive direction. However, after the pairing taste-CS and shock-US, a taste can acquire a signaling function for the upcoming electric shock, without hedonic shifts. We propose that taste stimuli employed as conditioned stimuli have two properties, i. e., sensory and emotional properties. Accordingly, animals learn relationships between a target taste and another stimulus by two different types of learning, the if-then strategy or the hedonic shift. This assumption is supported by physiological findings and the effects of specific hunger on taste aversion.

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Four groups of thirsty rats experienced Pavlovian conditioning during licking water. The experimental design was a factorial one. Two groups of rats received a short (0.7 s) shock as an unconditioned stimulus (US), while the other two groups received a longer shock (4.9 s). The one of each shock duration group experienced a pairing of conditioned stimulus (CS) and US once in a session of 5 min long, while another of each experienced three pairings in a session of 5 min long. Despite of more pairings of CS-US in the three-trial groups than in the one-trial groups, conditioned suppression was more prominent in the one-trial groups than the three-trial groups. These results suggest that many CS-US pairings did not generate greater conditioned suppression, rather deteriorated it, which was accounted by the trials spacing effect. The baseline licking levels, which were regarded as reflecting the associative strength of the context with the US, were more suppressed in the three-trial groups than the one-trial groups. The conditioned suppression of the three-trial groups did not differ from each other, which is consistent with previous studies of US duration effect; Differences in US duration did not affect the level of conditioning under a between-subjects design. In contrast, the long US generated the greater conditioned suppression to the CS than the short US in the one-trial groups. These results suggest that the effects of US duration may be manifested under the condition, in which the associative value of the context is fairly weak.

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Several studies showed the second order conditioning with a first order backward conditioned stimulus as a reinforcer established an excitatory conditioned response to the second order conditioned stimulus, while no excitation to the first order conditioned stimulus being observed. But other previous studies failed to show the similar effects in other situations. The present experiment addressed to retest the effects in the rats' licking suppression, in which a great part of procedures was similar to those used in the successful previous studies, except with on-the-baseline technique that had never been adopted in any previous studies. As the result, the second order excitation was observed but no eminently first order excitation was seen; i.e., the second order excitation with first order backward conditioning could be successfully demonstrated.

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The present report reviewed a short history of studies on variability in response and response sequence. Early research focused on the variability of a single response and found that variability in response topography may be a natural outcome of innate adaptive behavioral mechanisms. Subsequent studies shifted the research aim to produce variability in the response sequence by differential reinforcement. Early research failed to find enhanced variability in the response sequence. Rather, some studies showed a stereotyped response sequence and suspected that reinforcement created the stereotyped sequence. However, later studies proved that modification of training procedures and introduction of “Lag n” schedules improved variability in the response sequence. Two explanations were proposed. One was based on random selection of manipulanda and the other, on response selection probabilities. However, recent studies revealed shortcomings in both of them. The discussion addresses the need to form a new explanation to account for the findings. It also suggests some implications for future research including the use of variability measures to test higher-order cognitive processes.

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16 rats were tested in a runway to examine effects of memory load required for item association learning and serial position learning as a determinant of learning process in reward serial learning. Four groups of rats were trained with series A-A-B-N (Group 1-S), A-A-B-N and B-B-A-N (Group 2-S), A-A-A-A-A-B-N (Group 1-L), or A-A-A-A-A-B-N and B-B-B-B-B-A-N (Group 2-L) during acquisition. N symbolizes nonreward, and A and B were reward items which differed in quality. There were two test phases. In the item change test, the last part of the original series A-B-N and B-A-N was changed to A-A-N and B-B-N, respectively. In the position change test, the series were shortened by deleting their first items. Through these tests, it was suggested that Group 2-S learned serial position of nonreward, whereas the other three groups formed item associations between nonreward and preceding items. These results indicate that rats learn serial position of an item when both memory load for item association learning is high and for position learning is low, but in case memory load for position learning is high, they form item associations combining multiple item memory as discriminative cues for nonreward even under conditions where simple item cues are not available as signals. This finding suggests that rats can extract multiple types of information simultaneously from a series and can make decisions about learning strategies by comparing memory load required for the strategies.

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In three experiments, rats were exposed to a concurrent-chains schedule that differed both in terms of overall and relative reinforcement rates. Overall reinforcement rates were specified by high versus low absolute values of choice phase schedules. Relative reinforcement rates were specified by the ratio of choice phase schedules across four conditions (1 : 1, 1 : 2, 1 : 5, and 1 : 9) both in high and low overall reinforcement rate conditions. Experiments 1 and 3 used a forced-choice procedure in which relative and overall reinforcement rates were arranged by a single variable-interval schedule. Experiment 2 used a free-choice procedure in which relative and overall reinforcement rates were arranged by two independent variable-interval schedules. The fixed-interval schedules in the outcome phase did not differ between alternatives in Experiments 1 and 2, whereas the fixed-interval schedules differed in Experiment 3. When log response ratios were plotted against log reinforcement ratios, sensitivity to relative reinforcement rate under the forced-choice procedure varied with changes in overall reinforcement rate when the fixed-interval schedules differed between alternatives (Experiment 3), but did not vary when the fixed-interval schedules did not differ (Experiment 1). However, sensitivity to relative reinforcement rate obtained under the free-choice procedure varied even when the fixed-interval schedules did not differ (Experiment 2). These results suggest that the effects of overall reinforcement rate, the choice procedure as well as the length of the choice and outcome phases should be incorporated in modeling choices between alternatives associated with different reinforcement rates

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Perception of 'subjective contours', 'amodal completion', and 'transparency' is one of the controversial problems in human perception studies of the day. This paper attempts to outline the studies focused on perception of these phenomena in a variety of animals. Dozens of results have indicated that animals are capable of perceiving some of these phenomena except pigeons in amodal completion. It is also reported that perception of tested animals is comparable to that of humans'. Moreover, we reviewed some neurophysiological studies that examined some brain areas related to the perception. Our review of the studies suggest that the process for these perceptual phenomena is common among animals, including humans, and that process is involved in figure-ground segregation and surface perception. However, clarification of the process awaits further studies that directly compare humans and animals.

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Birdsong is a learned behavior. Song behavior has been analyzed from varieties of perspectives but how birds are listening to the song and behaving accordingly is relatively neglected. There are ample evidence from field observations that birds do remember vocalizations of conspecifics. Ecological approaches utilizing playback experiments revealed some species of males have a large memory capacity. In addition to these, we applied operant procedures and heart rate measurements to demonstrate auditory memory capacities in birds. How such memories are formed and where are they stored? A region of higher auditory area, the caudal-medial neostriatum (NCM), has properties that enable formation and maintenance of species specific vocal patterns. We propose combined behavioral-neuroanatomical approaches to understand ecologically valid processes of auditory memory formation.

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Weinvestigated how pigeons use auditory dimensions for discrimination of complex tunes. Six pigeons were trained to match two redundant auditory stimuli varied along two dimensions, “rhythm” and “timbre”, to two colors using a cross-modal symbolic matching-to-sample task. All pigeons learned this discrimination. The subjects matched the novel stimuli having new combination of each dimension's original values and the novel stimuli having the original “rhythms” and new “timbres”, based on the “rhythm” dimension. These results suggest that the pigeons are able to divide complex auditory stimuli into several dimensions, and that they paid more attention to the “rhythm” dimension. However, they matched the stimuli having the original “timbres” and new “rhythms”, to the color associated with the “rhythm” combined with the preserved “timbre” in the baseline discrimination. This result suggests that a dimension combined with a more salient dimension may become a conditional, or contextual cue for the discrimination of complex auditory stimuli in pigeons.

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Captive cotton-top tamarins produce variant forms of “long call” when separated from their social companions. In this article, vocal exchanges between familiar cotton-top tamarins during visual isolation were investigated experimentally. Two randomly selected subjects were separated from their colony, and were visually isolated into the separate cages in the same testing room. Antiphonal long calls within the restricted time period were more frequently observed between cage-paired tamarins than expected by chance. From this experimental finding, functional significances of the long calls during social isolation were discussed in conjunction with the previous findings in other primates of the New World, including tamarin and marmoset species.

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This paper reviews studies that investigated social learning of food preferences and aversions in rats. Many studies have found that rats can learn about food preferences by social processes. Rats exposed to a conspecific that had eaten a certain food increase their preferences for that food. On the other hand, the findings about social learning of food aversions are equivocal. Although poisoned conspecifics may function as unconditioned stimuli in food aversion learning, a few studies suggested that rats can socially transmit learned food aversions only under limited conditions. Finally, it is argued that researches of communication in ethology can complement those of social learning in psychology.

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Researches on play-fighting in rats, including issues on its behavioral characteristics, developmental change, and the functions of it were reviewed. It is suggested that the sequential analysis of behavior elements that construct play-fighitng is helpful in discriminating play-fighting from the serious fighting, though other investigations for characterizing this behavior pattern are also required. A recent study on ultrasonic vocalization which is emitted during play-fighting behavior is also considered as a way of characterizing play-fighting. More precise analyses on the relaionship between such vocalizations and agonistic behavior may help to identify the play-fighting behavior with higher accuracy. Studies on the developmental change of play-fighting indicates that it has little function of practice for the aggressive behavior in later adult stage, as has been supposed. Rather it might contribute to the normal development of the later sexual behavior, since some behavior elements shown by male juveniles appear to reflect the preparative stage of the reproductive behavior.

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This study is a replication of Awazu & Fujita (1998) which showed both the familiarity and the dominance between demonstrators and observers influenced on the social food transmission in rats, with some changes in the procedure. In the present study, observer rats were exposed to two demonstrators successively that had just eaten powdered chow having different flavors unfamiliar to observers, then subsequent preferences by the observers for these food items were tested in a choice situation. We found the same influence of dominance again; the observers preferred the food transmitted by the subordinate demonstrators to the food transmitted by the dominants. This effect of dominance ought to be a robust tendency. But we found no influence of familiarity in this experiment. The difference in the shape of the food between the previous and the present study may account for this inconsistency.

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It is well known that aged female monkeys show not only poor performance in cognitive tasks, but also low activity and social isolation. However, recent behavioral studies on aged monkeys living in social groups have emphasized that the process of social isolation is also influenced by dominance rank. To understand the effects of age and dominance rank, two hypotheses have been proposed. The “dominance history-stress hypothesis” (Veenema et al., 1997) maintains that the greater social withdrawal in low-ranking monkeys reflects a reduced ability to cope with complex social interactions, due to greater social stress influenced by their dominance history. On the other hand, Kato (1999) reported that the differences in social behavior between older high- and low-ranking animals are not due to social withdrawal by low-ranking animals, but rather to the social attractiveness of high-ranking animals (“dominance rank-attractiveness hypothesis”). To assess the validity of these two hypotheses, further studies on the relationships among dominance relation, stress, cognitive decline, and attractiveness with increasing age should be conducted.

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The present paper reviewed recent studies on the cognitive functions of aged monkeys as an aging model of cognition. It has been questioned that the aged monkeys did not always show substantial decline in cognitive abilities in some tasks. I could summarize the cognitive deficits in aged monkeys as the following points such as in spatial cognition task, temporal integration abilities of memory, learning set, and inability of inhibition. It became apparent that the aged monkeys took different behavioral strategies from the young in the other intact tasks. The better performances in aged monkeys could be attributable to such behavioral complement. Therefore, not only the ultimate performance in cognitive tasks, but the behavioral observations on learning process will be important to investigate the ability of aged monkeys. The longitudinal and multi-task studies will also be required to reach into the deep knowledge of cognition in aged monkeys.

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In this paper, we review the studies which aim to understand the effects of the central cholinergic manipulation on the temporal discrimination behavior. We start with a brief introduction of the tasks and their properties used in the studies of temporal discrimination. After that, we summarize the features of the studies in which the cognitive process theories are not considered. Then we sketch a representative cognitive model, “the information processing model, ” and summarize the features of the studies which were executed on the basis of this model. We clarify some distinctions between these two types of studies and point out the two variables which may cause those distinctions : the number of trainings under drug treatment and the potency of the drug. Next, we present our experiment in which the effects of these two variables on temporal discrimination were examined, and suggest some questions about the information processing model and the hypothesis of correspondence between the model and the cholinergic systems.

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This article reviews the brain mechanisms of taste aversion learning in the rat. First, behavioral experiments on taste aversion learning are reviewed. In this section, the experiment of Garcia and Koelling (1966), and the concepts of belongingness (Garcia et al., 1974) and preparedness (Seligman, 1970) are introduced. Then, studies in the field of behavioral neuroscience are reviewed and summarized. According to the results of several experiments, the parabrachial nucleus and the amygdala are suggested to play important roles in taste aversion learning. Finally, experiments on taste-potentiated odor aversion suggest that the amygdala could be a possible site where the selective associability in taste aversion learning occurs. This article offers implications for the mechanisms of taste aversion learning and information about its brain mechanisms for the fields of learning theory, ethology and for the clinical areas of phobias and anorexia.

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In this article, I discuss the process of navigation through reviewing the function of the primate parahippocampal cortex based on recent studies in humans and monkeys. Studies of brain damaged patients and of functional brain imaging suggest that the human parahippocampal cortex is involved in the scene recognition process. The parahippocampal cortex widely connects with other brain areas, including areas in the dorsal pathway as well as those in the ventral pathway. Monkeys damaged with the parahippocampal cortex are impaired on complex spatial memory tasks but on object recognition tasks. Neurons in the parahippocampal cortex respond to visual stimuli, and a few neuronal studies suggest the spatial function of the parahippocampal cortex. These studies suggest that the parahippocampal cortex is involved in the visuo-spatial processing. Further studies as to the role of the parahippocampal cortex will elucidate the scene recognition and navigation processes.

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It is thought that Pavlovian fear conditioning with electric shocks as unconditioned stimulus is an effective procedure to elucidate the neural substrates of learning and memory. In this paper, we start with a brief review on neural pathways of fear conditioning with an auditory or visual conditioned stimulus. Next, focusing on the amygdala that plays an critical role in these pathways, we present our experiment, in which we studied the role of subdivision of the amygdala in fear conditioning. As a result, it was obvious that two different neural pathways mediated the informations about input of the two conditioned stimulus; auditory and visual ones respectively, even if the same unconditioned stimulus; electric shock was used. Finally, we describe the future direction of the researches on this topic.

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The concept of “psychological well-being” was stated officially in US in 1985, for regulation of husbandry of nonhuman primates in the Amendment of Animal Welfare Act. This can be applied not to nonhuman primates but to other animals. One of the practical ways to establish the psychological well-being is the environmental enrichment. The environment enrichment aims to ensure that animals live in a captive environment which can provide opportunities to express more of their natural behavior. Recently, the improvements of husbandry with enrichment techniques are conducting in zoos and other institutions around the world. The effect of environmental operation always has to be evaluated and fed back to the next operation plan. However, the previous evaluation of the enrichment often lacked the viewpoint concerning the voluntary and sustenance of behavior. In artificial environment, there is a possibility to force animals to perform the arbitrary behavioral pattern, even if the appearance seems ideal. Therefore, this study reconfirmed the importance of the evaluation of “Selectability” and “Controllability” of the environment. Further, it was discussed that these indices are also quite effective to evaluate the enrichment for the laboratory and farm animals, which may be considerably different from the wild antecedents on behavioral pattern.

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