Chimpanzees (Pan troglodytes) that are kept in captivity come from a wide variety of backgrounds, and a proportion of them have been subjected to maternal separation and social deprivation during development. The long-term effects of such practices have received little investigation. This study investigates whether the removal of infants from their mothers and/or other chimpanzees affects their activity levels and abnormal behaviours later in life. A total of 69 resocialised chimpanzees were studied at six zoos in the United Kingdom. Chimpanzees were categorised into one of three rearing conditions: reared by their mother in a group of conspecifics (MGR); reared with other conspecifics but separated from their mothers (RO); and reared apart from their mother or other conspecifics for a period of time during infancy (RA). Results indicate that ‘socially deprived’ individuals show reduced levels of normal activity, elevated levels of abnormal behaviours and a wider repertoire of abnormal behaviours. These differences were more pronounced in younger individuals, with adults from the three different rearing conditions performing abnormal behaviour patterns at comparable levels. It is concluded that human-rearing, either alone or with conspecifics, influences behaviour through suppression of normal activity levels as a result of separation and elevation of levels of abnormal behaviours as a mechanism for coping with maternal loss and restricted rearing. However, these effects are not irreversible and recovery of ‘normal’ behaviours may occur with access to an enriched social environment.

The effects of maternal and peer separation during infancy and juvenescence on adolescent and adult chimpanzee behaviour were studied. The aim was to provide an insight into the social development of the species and to investigate human influence on this process. Forty-three adolescent and adult chimpanzees (Pan troglodytes), from a variety of backgrounds, were studied at five zoos in the UK. Details of play and grooming interactions were recorded. Competence at initiating, maintaining and contributing to play and grooming interactions was assessed. It was predicted that, regardless of their present environment, captive chimpanzees that were reared without their mother would be less competent and complex in these social abilities than mother-reared chimpanzees. Results indicated that the chimpanzees' social skills showed few detrimental effects of maternal separation. Nevertheless, individuals that had been human-reared demonstrated more unsuccessful initiations of social interactions and fewer polyadic grooming interactions than their mother-reared peers. Therefore, rearing background may have only a limited effect on adult chimpanzees' social competence. Adult chimpanzees that were hand-reared or nursery-reared may be exhibiting a recovery of their social skills, or they may be unaffected by their rearing background; alternatively, the effects of rearing may have been masked by more significant factors, such as current management.

Human infancy and early childhood is both a time of heightened brain plasticity and responsivity to the environment as well as a developmental period of dependency on caregivers for survival, nurturance, and stimulation. Across primate species and human evolutionary history, close contact between infants and caregivers is species-expected. As children develop, caregiver–child proximity patterns change as children become more autonomous. In addition to developmental changes, there is variation in caregiver–child proximity across cultures and families, with potential implications for child functioning. We propose that caregiver–child proximity is an important dimension for understanding early environments, given that interactions between children and their caregivers are a primary source of experience-dependent learning. We review approaches for operationalizing this construct (e.g., touch, physical distance) and highlight studies that illustrate how caregiver–child proximity can be measured. Drawing on the concepts proposed in dimensional models of adversity, we consider how caregiver–child proximity may contribute to our understanding of children’s early experiences. Finally, we discuss future directions in caregiver–child proximity research with the goal of understanding the link between early experiences and child adaptive and maladaptive functioning.

A ruminant's early experience with low-quality food (LQF) is expected to increase its acceptance and preference in adulthood. Contrarily, we found that experienced sheep (ES) exposed to mature oat hay early in life ate less of this LQF than inexperienced sheep (IS). A possibility is that ES might have devaluated the LQF through continuous comparisons against high-quality food (HQF) supplements (sunflower meal and ground corn) that were simultaneously available during early experience. In this study, we tested the devaluation hypothesis with a successive negative contrast (SNC) procedure. In a consummatory SNC procedure, ‘shift’ subjects are unexpectedly changed from HQF to LQF, and their consumption is then compared against the consumption of ‘unshift’ subjects that receive LQF all throughout the SNC procedure. The magnitude of the difference in consumption between preshift and postshift is regarded as a measure of the degree to which both foods (HQF and LQF) are perceived to differ hedonically. When sheep from our previous study were 300 days old, both ES and IS were randomly assigned to either shift (ES-S and IS-S) or unshift conditions (ES-U and IS-U; n = 6 in each group). Groups ES-S and IS-S were fed HQF (alfalfa hay) during the preshift phase, and then suddenly changed to LQF (oat hay) in the postshift phase. Groups ES-U and IS-U (controls) were fed only LQF throughout the SNC procedure. Subjects in ES-S showed a significantly lower intake of LQF than those in ES-U in the first postshift session (i.e. they showed an SNC effect), which was not observed in IS. These results agree with ES subjects having devalued LQF during early experience. We discuss the possibility that high levels of nutrient supplementation can result in devaluation of LQF (i.e. decrease in preference and acceptance), whereas restricted levels of supplementation may promote a positive experience with LQF.

Nutrition is an important aspect of welfare, and in most recommendations for the welfare of animals adequate nutrition is a primary requirement. However, in intensive livestock production systems the decision for adequate nutrition is made based on traditional paradigms of feeding monotonous rations or plant monocultures, frequently with excesses or imbalances of nutrients relative to the individuals’ physiology, which can compromise welfare. Individual ruminants can better meet their needs for nutrients and regulate their intake of secondary compounds when offered a variety of foods than when constrained to a single food, even if the food is nutritionally balanced. The concept of food variety is central because monotonous flavors and feeds and excess nutrients all cause animals to satiate, which in turn causes animals to eat a variety of foods. When offered a variety of foods, satiety for single foods stimulates the selection of a diverse diet and thus food intake, but when restricted to a monotonous diet satiety is aversive and limits food intake. Moreover, if a monotonous diet is aversive to animals then this could be stressful, even if monotony implies consuming a balanced diet. A diverse diet may also increase resistance to disease in ruminants, by allowing consumption of small amounts of compounds with antimicrobial/antiparasitic effects and immunity-enhancing properties. Herbivores also experience the benefits of ingesting compounds with medicinal (i.e. antiparasitic) benefits and they learn to prefer foods containing such compounds as their preferences are associatively conditioned by the food’s homeostatic utility to the body. Such learned patterns of behavior begin in utero and feeding experiences early in life cause changes – neurological, morphological and physiological – in animals, which influence on their subsequent behavior and welfare. Such experiences with the environment enable animals to adapt to local diets and stressors and reduce the levels of fear. Finally, feeding behavior in farm animals could be an aid in the early detection and mitigation of pain or sickness, and as such become an important tool in the identification of welfare and health of animals before the appearance of clinical signs. Management strategies in ruminant production systems could benefit by allowing animals to manifest their feeding preferences, thereby acknowledging the animals’ role as active players in feeding systems, instead of regarding them as passive entities that just respond to prescriptions and formulations.

The Strange Situation procedure was developed by Ainsworth two decades agoas a means of assessing the security of infant-parent attachment. Users of the procedureclaim that it provides a way of determining whether the infant has developed species-appropriate adaptive behavior as a result of rearing in an evolutionary appropriate context, characterized by a sensitively responsive parent. Only when the parent behaves in the sensitive, species-appropriate fashion is the baby said to behave in the adaptive or secure fashion. Furthermore, when infants are observed repeatedly in the Strange Situation,the pattern of behavior is said to be highly similar, and this pattern is said to predict the infants' future behavior in a diverse array of contexts. After an exhaustive review of the literature, it is shown that these popular claims are empirically unsupported in their strong form, and that the interpretations in terms of biological adaptationare misguided. There is little reliable evidence about the specific dimensions of parental behavior that affect Strange Situation behavior, although there does appear to be some relationship between these constructs. Temporal stability in security of attachment ishigh only when there is stability in family and caretaking circumstances. Likewise, patterns of Strange Situation behavior only have substantial predictive validity in similarly stable families. Implications for future research and theorizing — particularly as they relate to the use of evolutionary biology in psychological theory — are discussed.

Despite several decades of criticism, dichotomous thinking about behavioral development (the view that the behavioral phenotype can be partitioned into inherited and acquired components) remains widespread and influential. This is particularly true in study of birdsong development, where it has become increasingly common to diagnose songs, elements of songs, or precursors of songs (song templates) as either innate or learned on the basis of isolation-rearing experiments. The theory of sensory templates has encouraged both the dichotomous approach (by providing a role for genetic blueprints to guide song learning) and an emphasis on structural rather than functional aspects of song development. As a result, potentially important lines of investigation have been overlooked and the interpretation of existing data is often flawed. Evidence for a genetic origin of behavioral differences is frequently interpreted as evidence for the genetic determination of behavioral characters. The technique of isolation rearing remains the methodology of choice for many investigators, despite the fact that it offers only a rather crude analysis of the contribution of experience to song development and provides no information at all about genetic contributions to development. The latter could in principle be elucidated by the application of developmental-genetic techniques, but it is unlikely that these can easily be applied to the study of birdsong. Because developmental questions are so often posed in terms of the learned–innate dichotomy, “experience” is taken to be synonymous with “learning” and the possible role of nonobvious contributions to song development has largely been ignored. An alternative approach, based on Daniel Lehrman's interactionist theory of development, permits a more thorough appreciation of the problems that have yet to be addressed, and provides a more secure conceptual foundation for theories of song development.

A review of research with chicks, songbirds, rodents, and nonhuman primates indicates that the brain is lateralized for a number of behavioral functions. These findings can be understood in terms of three hypothetical brain processes derived from a brain model based on general systems theory: hemispheric activation, interhemispheric inhibition, and interhemispheric coupling.

Left-hemisphere activation occurs in songbirds and nonhuman primates in response to salient auditory or visual input, or when a communicative output is required. The right hemisphere is activated in rats when spatial performance is required, and in chicks when they are placed in an emotion-provoking situation. In rats and chicks interhemispheric activation and inhibition occur when there is an affective component in the environment (novelty, aversive conditioning) or when an emotional response is emitted (copulation, attack, killing). An interhemispheric coupling (correlation) found in rats and rabbits implies that the hemispheres are two major components in a control system with a negative feedback loop. Early-experience variables in rats can induce laterality in a symmetric brain or facilitate its development in an already biased brain.

It is predicted that functional lateralization, when present, will be similar across species: the left hemisphere will tend to be involved in communicative functions while the right hemisphere will respond to spatial and affective information; both hemispheres will often interact via activation-inhibition mechanisms when affective or emotional processes are involved. Homologous brain areas and their connecting callosal fibers must be intact at birth and must remain intact throughout development for lateralization to reach its maximum level. Injury to any portion of this unit will result in hemispheric redundancy rather than specialization. One major function of early experience is to provide stimulation during development, which acts to enhance the growth and development of the corpus callosum, thereby giving rise to a more specialized brain.

According to a “selective” (as opposed to “instructive”) model of human language capacity, people come to know more than they experience. The discrepancy between experience and eventual capacity (the “poverty of the stimulus”) is bridged by genetically provided information. Hence any hypothesis about the linguistic genotype (or “Universal Grammar,” UG) has consequences for what experience is needed and what form people's mature capacities (or “grammars”) will take. This BBS target article discusses the “trigger experience,” that is, the experience that actually affects a child's linguistic development. It is argued that this must be a subset of a child's total linguistic experience and hence that much of what a child hears has no consequence for the form of the eventual grammar. UG filters experience and provides an upper bound on what constitutes the triggering experience. This filtering effect can often be seen in the way linguistic capacity can change between generations. Children only need access to robust structures of minimal (“degree-0”) complexity. Everything can be learned from simple, unembedded “domains” (a grammatical concept involved in defining an expression's logical form). Children do not need access to more complex structures.