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Myowa-Yamakoshi M.,Kyoto University | Myowa-Yamakoshi M.,Japan Science and Technology Agency | Scola C.,Aix - Marseille University | Hirata S.,Hayashibara Biochemical Laboratories Inc. | Hirata S.,Kyoto University
Nature Communications | Year: 2012

Humans comprehend the actions of others by making inferences about intentional mental states of another. However, little is known about how this capacity develops and whether this is shared with other animals. Here we show the ontogenetic and evolutionary foundations of this ability by comparing the eye movements of 8-and 12-month-old human infants, adults and chimpanzees as they watched videos presenting goal-directed and non-goal-directed actions by an actor. We find that chimpanzees anticipate action goals in the same way as do human adults. Humans and chimpanzees, however, scan goal-directed actions differently. Humans, particularly infants, refer to actors' faces significantly more than do chimpanzees. In human adults, attentional allocation to an actor's face changes as the goal-directed actions proceed. In the case of non-goal-directed actions, human adults attend less often to faces relative to goal-directed actions. These findings indicate that humans have a predisposition to observe goal-directed actions by integrating information from the actor. © 2012 Macmillan Publishers Limited. All rights reserved.


Zamma K.,Hayashibara Biochemical Laboratories Inc.
Primates | Year: 2011

Grooming was observed in 11 wild chimpanzees (Pan troglodytes schweinfurthii) in Mahale, Tanzania, and the number of removal and stroke movements and grooming duration were recorded. Removal movements were more frequent during social grooming than during self-grooming. Chimpanzees used one or both hands for grooming, and grooming using both hands was more efficient for removing small objects. Due to physical constraints, self-grooming of the arms was almost always done using only one hand. The removal movement frequency during arm grooming was lower when self-grooming than when grooming another. They were more likely to use both hands during grooming another than during self-grooming, and fewer physical constraints during social grooming enabled a higher level of hygienic grooming. © 2011 Japan Monkey Centre and Springer.


Hayashi S.,University of Bonn | Carpenter K.,Prehistoric Museum | Watabe M.,Hayashibara Biochemical Laboratories Inc. | McWhinney L.A.,Denver Museum Nature and Science
Palaeontology | Year: 2012

The dinosaur Stegosaurus is characterized by osteoderms of alternating plates and terminal paired spikes. Previous studies have described the histological features and possible functions of these osteoderms. However, ontogenetic changes are poorly documented. In this study, the ontogenetic changes of the osteoderms are examined using eight different ontogenetic skeletons (a juvenile, a subadult, a young adult, and five old adults based on the cortical histology of their body skeletons). The juvenile plate and subadult spike show thin cortex and thick cancellous bone. The young adult plates have an extensive vascular network, which is also seen in old adults. Old adult spikes are different from old adult plates in having a thick cortex and a large axial channel. The cortical histology, in both plates and spikes, show well-vascularized bone tissue consisting of dense mineralized fibres in young adult forms. In old adult forms, the bone tissues in the spikes become more compact and are extensively remodelled. This might contribute to the structural reinforcement of the spikes. The plates in old adult forms also show extensive remodelling and lines of arrested growth, but only limited signs of compaction. The timing for acquisition of features seen in old adults is different between plates (an extensive vascular network in the young adult) and spikes (a thick cortex with a large axial channel in old adults). The result suggests that the timing for plate and spike functions is different. The extensive vascular networks seen in large plates suggest their function is for display and/or thermoregulation. The thick cortical bone of spikes of old adults suggests that spikes acquire a weapon function for defence ontogenetically late. © The Palaeontological Association.


Kano F.,Kyoto University | Kano F.,Japan Society for the Promotion of Science | Hirata S.,Hayashibara Biochemical Laboratories Inc. | Call J.,Max Planck Institute for Evolutionary Anthropology | Tomonaga M.,Kyoto University
Vision Research | Year: 2011

Although an extensive body of literature exists on the cognitive underpinnings of gaze movements in macaques and humans, few studies have investigated this topic from a broader evolutionary perspective. This study used the gap-overlap paradigm to examine the timing of the gaze movements by four hominid species: humans, chimpanzees, gorillas, and orangutans. The saccade latency involved in shifting the gaze from central to peripheral stimuli was measured and compared under two conditions, gap and overlap. The central stimulus disappeared shortly before the onset of the peripheral stimulus under the gap condition, but it remained under the overlap condition. Although all species demonstrated similar saccade latencies under the gap condition, the species clearly differed from one another under the overlap condition, which may suggest their similar perceptual and motor mechanism of making a saccade on the one hand and their differential strategies for coping with the competition between two activities involving fixation and initiation of a saccade (i.e. central vs. peripheral visual stimuli) on the other hand. In particular, humans showed longer saccade latency under the overlap condition compared to the other great apes, which may reflect this species' unique means of visual processing. © 2011 Elsevier Ltd.


Saneyoshi M.,Hayashibara Biochemical Laboratories Inc. | Watabe M.,Hayashibara Biochemical Laboratories Inc. | Suzuki S.,Hayashibara Biochemical Laboratories Inc. | Tsogtbaatar K.,Mongolian Academy of science
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2011

The formation processes of trace fossils - including shallow to deep pits, notches, borings (tunnels), and channels, particularly at the limb joints - observed on the surfaces of Velociraptor, Protoceratops, ankylosaurid, and Bagaceratops skeletons from Upper Cretaceous eolian deposits in the Gobi desert, Mongolia were investigated. The median diameters of these structures ranged from 5.25 to 7.68. mm. These structures were likely created by insects scavenging on dinosaur carcasses. This interpretation is corroborated by the presence of burrows of a size similar to the trace fossils observed on the dinosaur bone surfaces at the same locality. Broad borings (about 32. mm in diameter) created by small Mesozoic mammals have also been discovered on the ribs and scapulae of a Protoceratops skeleton. Dinosaur skeletons found at two localities, Tugrikin Shireh and Khermeen Tsav, and two formations, the Djadokhta Formation and Barun Goyot Formation, exhibited the same type of damage to the limb joints. The high frequency of trace fossils at the limb joints suggests that small animals targeted the collagen in the joint cartilage of dried dinosaur carcasses as a source of nitrogen, which was relatively scarce in the eolian environments of the Gobi desert during the Late Cretaceous. © 2011 Elsevier B.V.

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