Birds and primates typically attend to an object of interest using sensitive spots in the retina (i.e. the fovea). Therefore, the direction of their gaze indicates their focus of attention. Recent technological advances in miniature wearable devices allow us to examine birds' gaze behaviors in detail when they are freely moving, and even when they are flying. In this review, I aim to outline current knowledge about how birds use their gaze to attend to an object of interest, and what they are attending to when they are engaging in various natural activities, such as navigation, vigilance, and social interaction. I also aim to outline both strengths and limitations of techniques available for bird gaze-tracking. As a relevant example, I introduce a recent study that utilized Inertial Measurement Unit to examine how pigeons move their gaze while attending to landscapes and flockmates during their homing flights. Overall, I believe that recent sensor technologies offer a promising avenue for examining birds' visual attention and the associated mental processes in natural contexts.

Bats emit ultrasonic vocalizations through their mouths or nostrils, listen to echoes returning from surrounding objects, and reconstruct three-dimensional images to navigate in the dark. To perform the reconstruction, bats compare their original emission with returning echoes that have been changed by the surroundings. In natural environments, echolocating bats receive various sensory inputs, including insect echoes, clutter echoes, and pulses and echoes from other bats, which must create a complex acoustic situation. Here, we discuss how bats extract own faint echoes in the presence of noise, by focusing on three similar but different situations; auditory masking, clutter interference, and jamming. Sensitivity to faint echoes is maintained after intense pulse emission, by contraction of middle ear muscles during emission. Echoes from off-axis objects could be "defocused" by comparing spectral features in the pulses and echoes. In the presence of conspecifics, bats increase the intensity and duration of pulses to improve the signal-to-noise ratio of their own echoes. They also regulate spectrotemporal features of pulses to separate their own echoes from sounds of conspecifics. Some of the adaptations made by bats may have future engineering applications for radar or sonar systems.

Animal foraging behaviour has evolved in tight association with diverse forms of body structures species-specifically, because morphology shapes and affects perception, information processing, and subsequent motor control. Primates including humans possess skillful sensorimotor control such as tool-using, utilizing their arm-hand morphology. Birds also are capable of dexterous visually-guided behaviors despite the largely different body structures. This raises a question: what and how the body morphology constrains/facilitates behaviors in birds? The present article reviews research advance of sensorimotor control in birds. Specifically, it would be discussed about pecking, the analogous behavior to reaching and grasping in primates and tool-using. The author would suggest a research direction with the morpho-functional and embodiment views for comparative research on sensorimotor mechanisms underlying the dexterous foraging skills.

A sense of body ownership is essential in controlling one's own body in external space, which in turn may give rise to a sense of self-awareness. Body ownership in humans is sometimes extended to certain external objects apart from our own bodies, and such plastic changes in body ownership are thought to be the basis of tool use. Specifically, in a rubber hand illusion task, visuotactile stimuli from synchronous brush strokes to both participants' and rubber hands lead to illusory body ownership of the rubber hand and a shift of perception of the tactile stimuli to the rubber hand as a result of multisensory integration. Recent studies suggest that this kind of body ownership illusion occurs not only in humans but also in animals, including monkeys and mice. In addition, other studies have shown that body ownership is linked to empathy. Studying the body ownership illusion in humans and other animals, including models of human psychiatric disorders, will elucidate neural mechanisms underlying the sense of body ownership, which will consequently contribute to addressing the philosophical issue of self-awareness.

Octopuses, a member of molluscan class, possess well-developed nervous system such as lens eyes that is anatomically similar to our own, and the relative proportion of brain to body is equivalent to vertebrates. Octopuses are also characterized with their muscular highly sensitive sensory receptors, namely, suckers on their arms. Due to these biological uniqueness, octopuses have been a target for psychological studies and were reported their advanced abilities for learning and memory, which are achieved via visual and tactile perceptions. All of these findings have come from experiments that tested single sensory perception (i.e., visual or tactile). On the other hand, it is known in vertebrates that they can integrate multiple sensory information, by which they can vividly image their environments. In this review, we will briefly introduce our knowledge for biology of octopuses with special reference to their cognition, and we will shed light on an idea for cross-modal perception in octopuses, which is based on our on-going projects for visual and tactile learning, and manipulation of arms in tropical octopuses inhabiting the coastal waters of the Ryukyu Archipelago.

Rhythmic entrainment, or synchronization, to musical rhythm is universally observed in almost all human culture; however, in non-human animals, this kind of behavior has been demonstrated only by some specific species. Thus, exploring the evolutional origin and the psychological substrate for this capability is an attractive research topic. This article reviews recent studies tackling this question and relevant researches, then, introduces a hypothesis explaining the origin of the prominent capability for rhythmic synchronization in humans.

The saying "A dog (Canis familiaris) is man's best friend" and the term Jinba ittai (describing the connection between a horse ［Equus caballus］ and a human) express the affinitive interactions between humans and these animals. In this paper regarding psychology of learning, these interspecies interactions were considered to indicate that human behaviors change behaviors of these animals and vice versa. Such mutual influence is possible because humans and these animals have innate cognitive systems that allow them to process each other's behaviors, and because humans and these animals learn each other's behaviors. Thus, studies that investigated these cognitive systems and such learning were reviewed. Next, we looked at studies that examined these interspecies interactions during rearing or training. Finally, the reason why humans not only feel that dogs and horses can interact with them but also experience affinitive relationships with these animals was discussed. The innate and learned factors involved in the construction of these relationships were considered.

Social behavior is a conspecific interaction and plays an important role in the survival of animals. In contrast, while heterospecific interaction largely refers to predator ― prey interaction, occasional instances of cooperative behavior can be found, for example, the interaction between domesticated animals and humans. Domestication involves breeding animals for generations to familiarize them with humans without fear. A major behavioral characteristic of domesticated animals is tameness which is divided into two categories. One is reluctant to avoid humans (passive tameness) and the other actively approaches humans (active tameness). Until now, however, little is known about the genetic, behavioral and neurological basis of these two categories of tameness. Here, we briefly review genetic and neurological research on tameness. Next, we explore the relationship between tameness and social cognitive skills of domesticated animals, such as dogs. Finally, we discuss the possibility of the same brain regions being used in both conspecific and heterospecific interactions.

Naked mole-rats (Heterocephalus glaber) is a eusocial rodent, and their colony consists of a single breeding female (the queen), several breeding males, and sexually immature adults (subordinates). Mother animals in mammals trigger the onset of maternal behaviors by the surge of estrogen level through their gestation. On the other hand, caring of pups in the naked mole-rat colony is not performed by the queen, but non-reproductive subordinates. The paper reviews the mechanisms by which subordinates trigger the onset of maternal behaviors and the queen decreases maternal behavior. Even though female subordinates can not synthesize estrogen from the placenta, their urinary estrogen concentration during the queen's gestation period was higher than during the queen's nonlactating period. Naked mole-rats routinely eat feces (coprophagy) excreted by other individuals, including those from the queen. The feces of queen included more estrogen during her gestation period than her non-lactating period. Furthermore, by oral ingestion of estrogen, subordinates increased the urinary estrogen concentration and enhanced the maternal response to pup vocalizations. These results suggest that subordinates ingest estrogen to trigger the onset of maternal behaviors through the coprophagy of pregnant queen feces. When subordinates became reproductive by separation from the queen and gave birth to pups, they decrease the number of maternal behaviors. Therefore, the queen does not innately unmotivated to care pups in innate and might acquire the neural changes to decrease maternal behaviors. It is reported that there are gene expression ifferences in the brain between the queen and subordinates. The gene expression associated with synthesis and reuptake of dopamine is upregulated in the queen's brain, such as tyrosine hydroxylase gene and dopamine transporter gene. However, the gene expression of dopamine receptor D1 and D2 are decreased in the brain of the queen, compared with subordinates. Dopamine receptor D1 and D2 are expressed in the striatum including nucleus accumbens and regulate the amount of maternal behavior in reproducing females. Taken together, the motherhood in naked mole-rats might be enhanced by the surge of estrogen level through the coprophagy and be restrained by the inhibition of dopamine receptor D1 and D2 gene expressions.

Cephalopod have large brain, lens eyes and numerous chromatophore. They accomplish observational learning with this information processing system. In spite of sharing the well-developed system, there are big variations for their cognitive ability among octopus and squid. Solitary and benthic octopus should have good spatial cognition with their long arms. On the other hand, gregarious and nektonic squid should have good communication ability with school members. Although knowledge about inter-individual relationship of squids will help deep understanding of communication, there are few information about schooling behavior of squid despite much accumulation of knowledge about octopus cognitive ability. This article reviews studies for schooling behavior of oval squid, Sepioteuthis lessoniana. Through social network analysis, basic structure of their inter-individual relationship is uncovered. Understanding of communication for squid with the knowledge about schooling behavior will contribute to understand evolution of cephalopod cognitive ability.

The field of comparative cognitive science has focused especially on mammals and some birds because of their phylogenetic closeness with humans and their larger brain compared to "lower vertebrates" such as fish. However, recent comparative analyses and conceptual models in the field of animal psychology and/or animal behavior propose that cognitive abilities have evolved in response to ecological and/or social factors. In addition, it has been shown that brain organization are largely conserved throughout the vertebrates, suggesting that lower vertebrates may have more sophisticated cognitive abilities than previously thought. Therefore, to reveal the phylogenetic distribution of cognitive abilities we should also examine lower vertebrates. In fact, ethologists have demonstrated diversity of social and ecological complexities in fish, which are good candidate for helping to reveal how cognitive abilities evolved. Therefore, I focus on fish cognition in this review. Recent studies have shown that some fish behave depending on the types of information they receive. As examples, I introduce studies about flexible decision-making and social cognitive abilities in cichlid fish in Lake Tanganyika, and cleaner wrasse. Finally, I discuss the evolution of cognitive abilities in different ecological contexts.

Social intelligence hypotheses propose that complex socialization drives cognitive ability, which animals use to solve the problems associated with complex societies. However, studies of social intelligence have, so far, been limited to a few species, and further studies are needed to discuss "why" social intelligence has evolved in species that have adapted to various environments. Bottlenose dolphins are thought to have complex social systems and cognitive abilities. The evolution of their social intelligence in underwater environments is very different from that of terrestrial animals such as humans and apes. In this paper, we review several social intelligence studies of wild and captive bottlenose dolphins that encompass social interactions ― including affiliative, agonistic interactions and post-conflict affiliations ― and cognitive abilities ― including cooperation, prosocial behavior and joint attention. We also discuss further scope for research on the social intelligence of dolphins.

With the accumulation of knowledge regarding sociality of animals, social enrichment is regarded as one of the most important part of captive animal care. Although the basic knowledge has been accumulated, sociality involves complex issues. Moreover, practical methodologies for social management remain controversial. In this paper, we overview the current studies and practices of social management on four great ape species (chimpanzees, western lowland gorillas, and Bornean and Sumatran orangutans) housed in Japanese zoos to advance the sociality discussion. We first describe the fundamentals of sociality in animals. Then we explore important topics of sociality, including social relationships in captivity, all male group formation in chimpanzees and gorillas, group living in orangutans, and welfare of disabled and geriatric individuals. Although the number of sociality studies has recently increased, to maximize the positive effects of captive social living, more detailed understanding of the effects of social factors on animals using scientific methodologies is important.