A property of human language associates words or labels each other according to several arbitrary rules. However, we do not know what cognitive abilities produce this property in humans. Through hierarchical concept acquisition, in this study we investigated the cause of this property in non-human animals, Capuchin monkeys (Cebus apella). First, we trained the subjects to acquire four component concepts with symbolic matching-to-sample (SMTS) procedures. Next, we trained the subjects to acquire two higher-order concepts including four acquired component concepts. The monkeys had to learn the relations between the examples of four component and two higher-order concepts and geometrical figures used as symbols in the SMTS tasks. Thereafter, we tested whether the monkeys spontaneously acquire relations among symbols similar with the hierarchy among concepts without particular training. Test results indicated that the monkeys understood that the symbols associated with component concepts were in relation to the symbols associated with higher-order concepts; on the other hand, they showed no evidence of understanding the opposite relations. It suggests that they could find an association among symbols based on hierarchy among concepts; however, their ability to grasp associations among symbols based on arbitrary rules was limited compared to humans.

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Bi-directional communication occurs in a variety of unrelated taxa, suggesting multiple independent evolutionary origins. However, this form of communication is relatively rare. Turn-taking is a prerequisite for successful one-dimensional signal transmission in animal communication. When many signaling individuals occur together, reply latency between first and second signalers is key to establishing communication. Existing literature shows that turn-taking behavior in animals can be classified into three categories based on the relationships between the signaler and the receiver: chorus, duet, or antiphony. Chorus involves males only; duet involves male-female pairs; and antiphony occurs in any animal combination. The functions of the signals can be for mate attraction, individual or group identification, or resource protection. An earlier hypothesis on insect duets suggests that male chorus behavior evolved into duet behavior under the influence of interwoven natural and sexual selection pressure. We discuss putative convergent evolutionary processes in turn-taking behaviors that occur in species other than insects (including humans), and conclude that the processes may be similar across taxa. Moreover, antiphony may have evolved from duetting.

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Vocal learning ability has evolved in a limited range of vertebrates, including some lineages of birds, bats, and whales. In birds, vocal learning contributes to the development of song, which is related to reproductive context. Birdsong is regarded as a sexual trait acquired through sexual selection. Generally, only male birds produce songs, and females prefer to mate with males that have elaborate songs. If song is an honest indicator of male quality, it is adaptive for female birds to choose a mate based on his song performance. To shed light on the evolution of song learning, we review the literature for both phylogenetic studies that reconstruct the evolutionary patterns of song traits and studies of behavioral ecology that consider selection pressures by investigating the costs (e.g., developmental stress) of producing complex songs. Furthermore, we discuss the evolution of song in two songbird species, the white-rumped munia and its domesticated strain, the Bengalese finch. The two strains differ in morphology and song, probably because domestication has modified selection pressures.

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Week-old chicks quickly learn to peck colored beads when reinforced by food rewards. In binary choice tests, the trained chicks made choices based on anticipated values of foraging efficiency. Two forebrain regions proved to be involved in the anticipation, i.e., ventral striatum ⁄ nucleus accumbens complex (basal ganglia) and arcopallium (an association area of lateral forebrain). Localized lesions of the basal ganglia caused an impulsive choice away from a long waiting time. On the other hand, lesions of the association area caused an impulsive choice away from a long consumption time. These results suggest that 1) chicks make choices based on foraging efficiency, in which sum of the waiting time (or time-to-reward) and the consumption time (or work cost) serve significant denominator, and 2) these two time domains have distinct neural substrates, thus are assumed to be neuro-ecologically distinct factors.

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Most of behavioral patterns in animals can be interpreted as passive mechanical reactions to stimuli. This idea of Innate Release Mechanism dominated in ethology for a long time. However, if all types of behavior were caused by this mechanism only, animals would not survive in any novel situation where some new behaviors become necessary. Contrary to the traditional theory, we demonstrate that pill bugs (Armadillidium vulgare, Isopoda, Crustacean) can adapt to a new situation by spontaneously generating a new (special) behavior. In our experiments, each bug was placed to an annulus-shaped substrate surrounded by water (test conditions) or acrylic wall (control conditions). Small obstacles were introduced at regular intervals in the middle of the annulus. Normally, the bugs move in a well-known turn-alternation behavioral pattern, touching the obstacle repeatedly. However, as they are destined to die staying in water for more than about thirty minutes, moving along the water becomes dangerous but crucial for their survival activity, resulting in the emergence of the new type of behavior. Under such conditions, the bugs demonstrated mounting to the obstacles, i.e. the behavior rarely observed in the absence of water. Sometimes, this mounting behavior was observed recurrently after wandering around obstacles without touching the water. In the control experiment, when the annulus substrate was surrounded by acrylic wall, mounting behavior happened rarely. We further study the time series corresponding to the behavioral pattern of touching the obstacles by means of wavelet analysis, in order to reveal characteristic periods of each kind of behavior under different conditions. Several pronounced periods in the interval of 50-200 seconds have been detected in both the experimental and control groups. This result implies that pill bugs scan the environment with certain periods, and express mounting behavior occasionally. In the presence of water, mounting behavior apparently decreases the probability of direct contact with the water. Expression of this kind of adaptive multiple-choice behavior can be interpreted as an “intelligent” activity of pill bugs.

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Animal individuals should have rationality in the sense that they can behave adaptively to their environments, executing various tasks concerning reproduction and⁄or survival. Such rationality as exhibited by animals is called “ratiomorph”, when it may not be attributed to their conscious thinking. A ratiomorph is considered to have been implemented by means of certain physiological mechanisms, which have been subjected to various selection pressures for animal cognitive capacities. In the present study, we conducted computer simulations on models of ratiomorphic mechanisms and a simple stimulus-response (SR) rule; a modal behavior pattern of the pill bug called “Turn Alternation” (TA) response is modeled as an example of ratiomorphic behavior. In the TA behavior, a pill bug turns to left and right alternately. It has been suggested that one of the simplest and the most plausible explanations of the TA response is the Bilaterally Asymmetrical Leg Movements (BALM). We constructed computer models to reproduce the pill bug's behavior by formulating the BALM mechanism as logical formulas and transforming them into dynamical systems. Our models can be recognized as expressions of ratiomorphic property of the pill bug in terms that “rationality”, expressed as logical formulas, is implemented in the forms of dynamical systems, and produced more diverse behaviors than the model based on the SR rule. From the results of our computer simulations, it is suggested that an animal with ratiomorphic mechanism may carry flexibility and cognitive aspects in its behavior.

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An individual having a Theory of Mind (ToM) can read the minds of others. If we assume further that the individual considers each of them also to have a ToM, then there should be recursive structure here. We believe that emergence and evolution of this structure are deeply linked to the evolution of intelligence. We construct two computational models: an abstract model describing fitness landscapes interacting with each other and a concrete model describing physically-situated agents moving around avoiding collisions. We conduct evolutionary simulations using the concrete model in order to investigate the dynamics inherent in the mechanism of recursion. Several unexpected properties of recursion were found, including a significant difference in fitness between odd levels and even levels of recursion. This is due to the asymmetry between level 0 and 1 (without and with ToM). We also discuss an evolution scenario in which human beings have evolved the ToM.

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It is well known that children can learn words rapidly. Recently, several studies suggested that knowledge about the relationship between vocabulary and perceptual objects works as a constraint to enable children to generalize novel words quickly. Many experimental results of novel word generalization task supported this hypothesis, but its mechanism remains unclear. In this study, we examined a past proposed model explaining its mechanism and showed that they could not simulate novel word generalization task well in certain conditions. Therefore, in stead of the previous model, we proposed a model that could learn optimal feature attention for specific prototype. Our proposed model works well even with a multidimensional vocabulary set including rich perceptual information that the past model could not work. It suggested that statistical learning could be powerful enough to solve feature selection problem even in noisy information source. Furthermore, it also suggested that the basis of chilren's word learning was prototype-specific feature attention.

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This study investigated the forming process of the sentence semantic representation. Fujiki and Chujo (2005) consider it the integration process of schemata. Their model assumed that the integration occurred when encountering syntactic head words of phrases, and that the schemata of the constituents except the head were integrated into the head schema. However, their model could explain only two types of integration, so this study extended the model including the process of comparison and alignment for schemata. To test the validity of this extended model, we compared sentences including acceptable noun phrases with sentences including unacceptable noun phrase. As the result of the measuring the reading time of those noun phrases and judgment time of the acceptability of those sentences, the semantic processes of these sentences changed depending on the load of sentence processing. We proposed that the model would change its behavior as the amount of the available resources changed

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During reading spaced text such as English, each word is not refixated very often when eyes initially land on slightly right side of the middle part of the word. However, in identifying an isolated word, the word will be identified more quickly when eyes initially land on slightly left side of the middle part of it. These two initial eye landing positions are called optimal viewing position or OVP, and these two phenomena are called optimal viewing position effect or OVP effect. This paper aims to simulate eye movements using a computer to realize these two OVP effects. Previous studies indicated that the reason for OVP in identifying an isolated word was that letters could be identified more correctly in the right visual field than the left. In our study, in order to get the higher probability of letter identification in the right visual field than the left one, we considered the asymmetry of the number of pixels sampled in the left and right visual field. And we used the gap between subjective and objective viewpoints to quantify the asymmetry. Here, a subjective viewpoint is defined as the point that people look at on an object. Meanwhile an objective viewpoint is defined as the point of the object, on which the straight line passing through the center of pupil and fovea falls. In our experiments, eye movements in identifying an isolated English word and reading English text were simulated using a computer while shifting the objective viewpoint around the subjective viewpoint. As a result, OVP appeared on the left half of a word and on the right half when identifying an isolated English word and reading English text, respectively. These happened only when the objective viewpoint was shifted to the right from the subjective viewpoint by the width of 1 letter.

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This paper indicates that the induction field in vision can predict regibility of character with various resolusion. Recently, it is popular to read electric document on the display device. So, character regibility on display with various resolusion has been focused on as a good display condition. However, there is not enough basic evaluating between character regibility and resolusion. Many previous research activities only suggest relationship between regibility and resolusion. This paper first confirm the relationship by psychological experiment. Then, to explain the experimental result, complexity of induction field corrected by stroke width of character was examined. It is indicated that the corrected complexity using induction field can evaluate regibility of character with various resolusion.

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Optical topography (OT), reported in 1995, is a spectroscopic method for noninvasive imaging of brain function. The technique has advantages in safety and lower constraint for subjects compared to other brain imaging methods. In addition, only a simple and easy system is needed for the measurements. These advantages made it possible to approach new themes such as measuring brain function of infants, which had been difficult with conventional techniques. This paper introduces the principle of OT and some representative OT studies, and observes on the current problems and landscapes in OT studies.

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