Yoichi Sakai

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With the goal of developing a conversational humanoid that can serve as a companion for people with dementia, we propose an autonomous virtual agent that can generate backchannel feedback, such as head nods and verbal acknowledgement, on the basis of acoustic information in the user's speech. The system is also capable of speech recognition and language(More)
With the increasing average life expectancy of world population, there are more and more dementia patients, and the needs of assistive technology emerges. According to the literature, the progress of cognitive impairment can be suppressed to be slower if the patients is constantly in calm mood. An effective way is suggested by keeping them in social(More)
Protogynous hermaphroditism, female-to-male sex change, is well known among reef fishes where large males monopolize harems of females. When the dominant male disappears from a harem, the largest female may change sex within a few weeks. Recently, from experiments with some protogynous haremic fishes in which two males' cohabitated, it was confirmed that(More)
Mimesis is a relatively widespread phenomenon among reef fish, but the ontogenetic processes relevant for mimetic associations in fish are still poorly understood. In the present study, the allometric growth of two allopatric leaf-mimetic species of ephippid fishes, Chaetodipterus faber from the Atlantic and Platax orbicularis from the Indo-Pacific, was(More)
We tested the hypothesis that the highly flexible feeding repertoire of juvenile Chaetodipterus faber reflects their trophic adaptability by quantifying the feeding behaviour of juveniles in situ, for the first time, in a northeastern Brazilian estuary. The fishes presented a preference for alga-rich habitats, irrespective of the substrate type chosen(More)
This study revealed the spatial variation in abundance and body size of larval fishes in the Seto Inland Sea, Japan, in January 2014 and 2015. Fish larvae were collected by a 1.3-m-diameter ring net towed at the surface and at 10-m depth at 21 stations. The most dominant species was the sandlance Ammodytes japonicus, constituting 82% of total larval fish(More)
The Asian sheephead wrasse, Semicossyphus reticulatus, is the largest labrid in temperate waters around Japan. However, the growth pattern of this wrasse remains unclear. Age, growth, and reproduction of S. reticulatus specimens were investigated by sampling in the western Seto Inland Sea, Japan. Opaque ring marks formed on the marginal zone of sectioned(More)
Whereas mating behaviors and social structure have been studied extensively in monogamous hermaphroditic gobiid species, such studies are relatively limited for polygamous gobiid species. To investigate the reproductive strategy of polygamous gobies, mating groups of the common fusegoby Fusigobius neophytus were observed on reefs of Kuchierabu-jima Island,(More)
The mating system of cirrhitids is generally classified as harem polygyny. However, detailed information on the spatial distribution patterns and mating relationships is lacking in large hawkfish species. We investigated the spatial distribution patterns and mating relationships among individuals of the large hawkfish, Paracirrhites forsteri, on a(More)