Empirical studies on behavior using animal models provide irreplaceable tools for dissecting intricate neural circuits into multiple output modules that concomitantly regulate segmented components of behavior. Recent technical advancement in the manipulation and measurement of neural cell/circuit activities in freely behaving animals allow us to bridge the gap between neural processes and behavior expression. While neural signals are processed on the second timescales, the nature of behavior is time-consuming effort to gain interaction with environmental stimuli for adaptation. Therefore, a bundle of neural activities cannot simply represent entire behavioral processes, but rather segmented behavior components. Hence, we must reconsider how such bundles compose total outputs forming functional set of behavior, and thus, how integrated behavior can be broken into neural modular components, such as sensory detection, element recognition, behavior drive, and action/movement execution, by neural activity timescale units. Our refined protocol on behavioral studies is more effective in terms of determining what we observe in animal behavior and how we interpret neuro behavior relationship for vital contribution to basic and translational studies.

Among all mammals, infants are born immature and require parental care for survival. Infants have an innate motivation to maintain proximity with their caregivers through a physical approach and signaling their needs, which is collectively called the attachment system. Infants' attachment behavior promotes caregivers' parental behavior. The present review introduces research on the mechanisms underlying human parental and attachment behavior using rodents and primates as animal models. Especially, a New World monkey, the common marmoset (Callithrix jacchus) is a promising primate model. Unusually for other non-human primates, marmosets share infant care with family members including the mother, father, and older siblings. Their parental and attachment behaviors show many similarities with those of humans. Additionally, we discuss atypical behaviors in artificially reared marmosets as a model of insufficient parenting in comparison to disorganized attachment and attachment disorders in humans. Therefore, the marmoset is an ideal animal model for revealing the brain mechanisms of parental and attachment behaviors.

The degu is a species of rodent that communally rears its pups. While experimental social separation in the preweaning period has been reported to cause hyperactivity and disrupt brain function, it remains unclear how degu pups' behavior and their central nervous system are influenced by different naturally occurring nurturing behaviors. The present article reviews the effects of different parental behaviors and experimental social separation on degu pups from behavioral and neural perspectives. Moreover, as a case study, we observed pups born to two mothers who exhibited different nurturing behaviors. The pups that received less maternal care showed fewer days on which audible vocalizations were observed and fewer rearing behaviors (standing on both hind paws) than pups that received more maternal care. These behavioral tendencies differed from those reported in an experimental social isolation study. We expect that not only the effects of the experimental social separation but also the short- and long-term effects of naturally occurring differences in nurturing behavior on degu pup development can be studied with the consideration of ecological validity.

In reviewing mother-immature offspring in Japanese macaques (Macaca fuscata), this article first characterizes Japanese macaque birth as a quiet and solitary event, but one which does not occur in isolation from other group members. It then summarizes mother-infant relationships during their first year after birth, during which initially completely dependent infants gradually develop independence from their mothers. It also describes the relationships between maternal aggression and infant dependence, and maternal dorsal carriage. While the influence of factors such as mother's parity and dominance rank and infant's sex on motherinfant relationships has been studied, individual maternal styles might be a stronger influence on mother-infant interactions. The article also describes flexible and appropriate responses of mothers to their injured or congenitally disabled infants. Adoptions of dependent infants by non-mother females, and adult male-care of infants are reviewed. Finally, the importance of two types of studies for more fully understanding mother-immature offspring relationships in nonhuman primates is stressed; namely, empirical studies with clear aims, hypotheses and data collection methods, and careful record-keeping of rarely observed behaviors or events.

Great apes (seven species of three genera) and humans are categorized as Hominidae, based on their genetic closeness. Thus, comparative studies on great apes provide useful insights to understand the evolutionary origin of human nature. Although great apes differ greatly in terms of their behaviors and social structures, the mother-infant relationship is fundamental to the survival of offspring and support its cognitive development among Hominidae in general. In this review, I will report the diversity among great apes and will highlight the features of human mothering illuminated by the species comparison. Mothering has been supported by other social factors and relationships, but the modern human society often puts too much emphasis on the mother who is isolated from other members of the community.

From a biological perspective, maternal behavior is widely considered instinctive, because death of children who inherit their own genes should be avoid. However, in many species, include humans, maternal behavior exhibits a degree of fragility. This vulnerability can be attributed to "byproduct" of parental investment regulation mechanisms that depend on estimates of reproductive success. Adverse factors affecting reproduction, such as environmental deterioration and social stress, have the capacity to inhibit hormonal functions and suppress the expression of maternal behavior, as hormones during pregnancy and lactation play a pivotal role in shaping maternal behavior. In other words, maternal behavior is modulated based on contextual factors, and when the prospects for successful reproduction appear bleak, the abandonment of child-rearing may ensue. This concept, referred to as "differential allocation of parental investment," brings the notion that maladaptive parenting can happen to anyone under specific conditions, and deeper understanding and empathy for parents who raise their children inappropriately. Nevertheless, it is important to acknowledge the potential for its inappropriate dissemination due to a lack of understanding, which, in turn, could lead to unjustified prejudice and stigmatization. Consequently, we are exploring strategies for the appropriate utilization of this information within clinical psychological settings.

Vocal interaction between parents and offspring plays a critical role in songbirds' parental care. Raising young birds involves various aspects, including not only egg incubation, temperature regulation, nest maintenance, and feeding but also the vital role of imparting a tutor song that is crucial for future mate selection and the establishment of social bonds. This manuscript focuses on two species, zebra finches and Bengalese finches, which have been extensively studied in the broad research field spanning from their neural mechanisms to evolutionary significance, and provides a comprehensive overview of how vocalizations from parents and offspring play important roles in their parental care, as well as the influence of paretal behaviors on vocal learning and production in offspring.

Horses (Equus caballus) live in stable groups and are known as a species whose strong social bonds between unrelated female group members increase both foal birth and survival rates. In mammals, the origin of social bonds lies in the mother-infant interaction. Therefore, it is important to study the mother-infant relationship of horses to understand the developmental basis of social bond formation. In this paper, we describe the pregnancy, parturition, maternal and allomaternal care, of horses. We also describe the pregnancy, parturition, maternal and allomaternal care, of zebras (E. quagga, E. zebra, E. grevyi), a close relative of the equine species. Then, we summarize the characteristics of horses' maternal and allomaternal care by comparing them with those of zebras from the perspectives of domestication, habitat, and group stability. Finally, we propose some possible future studies to explore equine or follower-type ungulates' maternal and allomaternal care by referring to the importance of comparing maternal care and allomaternal care of follower-type horses with those of the other follower-type and hider-type ungulates.

Cats are now the most common companion animal in Japan. Cats have had a close relationship with humans for a long time, and sometimes there is human intervention from the earliest stages of development. In other words, they are often raised by humans rather than by their biological mother. Cats raised by humans may perform the same behaviors in humans that they do in their mother cats. This paper outlines cat parenting by biological parents and its mother-infant communication and human-cat "mother-infant" communication, followed by a summary of maternal-like behaviors exhibited by cats toward humans. The process of parenting by cats and the developmental stages of their offspring are outlined, followed by an explanation of the recently revealed role of the father and communication between mother and offspring. Regarding cat parenting by humans, the importance of the socialization period will be discussed, followed by an explanation of various forms of "motherinfant" communication. Then, after summarizing the mother-like behavior of cats toward humans, I will discuss whether cats show tolerance toward human children based on preliminary studies and my own experience. Finally, I summarized the differences between conspecific and inter-species communication and discuss future prospects.

Extensive studies on dog development were conducted during the 1950s and 1960s, revealing that the behavioral characteristics of adult dogs, particularly their fear towards humans, are significantly influenced by their social contacts, including with humans, during their developmental period. Recently, the importance of the quality of the early developmental environments, especially the mother-infant relationship, has become a focus of attention, as dogs as companion animals are required to have a harmonious temperament in their daily lives with humans. In this article, we first explain the significance of studying stress responsiveness in dogs and introduce our research on the development of stress responsiveness in dogs and the exploration of maternal factors based on findings in rodent studies. Finally, I would like to share our experiences on dog birth and raising them, in which we have been involved personally.