Cognitive abilities of elephants had not been studied so much until recently despite many anecdotal evidence of their enormous potentialities. But today, more and more researchers are becoming interested in studying their cognition, especially their general intelligence, memory, and numerical cognition. Genetically elephants are more closely related to the small-brained aardvarks and manatees than to primates, but a few evidence indicate that their cognitive ability is comparable to that of apes. We aim to introduce series of recent work on elephants and some suggestions for future studies. Especially, we would like to point out the importance of studying their cognition from the point of view of field of human language evolution and animal welfare in captivity.

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A few years ago, the entire human genome was decoded, and this information constitutes our blueprint. We have benefited from this genome-sequence information in various ways, including the development of new drugs and advances in molecular biological technology. However, we still do not know how the “human mind” has evolved, or the biological basis of cognition in humans. It may be difficult to determine the biological features of humans without comparison with other species. It is important to compare differences in cognition and genomes among species and to conduct association studies in order to understand the human mind. In this review, we introduce recent topics related to interaction between the cognitive sciences and genome information and discuss the possibilities of molecular biological approaches in comparative cognitive science.

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After evaluating the history of comparative or animal psychology in Japan, a development over the past 150 years, four distinct generations of comparative psychologists can be discerned in terms of their active involvement in the field. The zero generation, spanning the second half of the 19th century, was marked by the import of Darwinian evolutionary theory, which was implemented especially through lectures by Edward S. Morse. The first generation appeared in the early 20th century, with Koreshige Masuda heralded as the foremost comparative psychologist during this time. The 1.5-generation researchers were influenced by Gestalt psychology, which had been developed in Europe. The second generation emerged after World War II with the arrival of neobehavioristic psychology. Originated in the U. S., it was studied by comparative psychologists such as C. L. Hull and B. F. Skinner, who considerably influenced Japan's post-war generation. The third generation of comparative psychologists in Japan took root in the 1980s and was characterized by studies of cognitive process. Due to space limitations, the zero and first generations are solely detailed here.

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Social ability seems to play a major role in the ontogeny of language. Human babies are already sensitive to adults' eye gaze, and follow it at an early age. At the first year of life, they begin to redirect the adults' attention and actively establish joint attention with caregivers and other important adults. They then use the established joint attention to guess meanings of words they hear. Later, children further show socio-pragmatic ability at a higher level to guess word meanings. They still use joint attention but they may not depend upon joint attention in some situations. Flow-of-conversation and guessing others' internal conditions can also give important cues for language development.

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The sophisticated feature of human speech allows us to turn much information encoded by language in the brain into sounds and to communicate it with others rapidly and efficiently. Human speech shows highly sophisticated modifications of supralaryngeal vocal tract (SVT) in volume and shape, through voluntary regulation of the vocal apparatuses, which is usually regulated involuntarily in other mammals. Paleoanthropologists have continued to debate the “origin” of language, evaluating distinct morphological features, which are presumed to underlie just human speech, but such continued efforts have no consensus on the age of the origin. On the other hand, recent advances in empirical studies on the development of the SVT anatomy in nonhuman primates endorse the idea that many of the separate biological foundations of speech had evolved independently before the origin of human beings, under different selection pressures unrelated to speech. The efforts have contributed to our better understanding on the mosaic processes of the speech evolution, and could contribute greatly to exploring the long “evolutionary history” of speech.

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In this paper, we propose three hypotheses about language understanding. One of the fundamental and important components of language processing is assignment of a thematic role to each word in a sentence, based on word order and particles or prepositions. Therefore, we first discuss the brain mechanism of thematic role assignment, followed by a discussion of the brain mechanism for outlining the meaning of a sentence. We then evaluate the function of the mirror neuron system in language understanding. Finally, we discuss the brain mechanisms of mental perspective shift and hierarchical processing in language comprehension.

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