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Animals, including horses may be valuable partners in many activities, pedagogy and therapy. Contact between humans and animals can facilitate an oxytocin secretion that, as a consequence, may alleviates stress-responses, increases social orientation and that supports attachment and caregiving. These mechanisms can be utilized in animal-assisted therapy, for example, to enhance trust between client and therapist and to help increase attachment security in clients with insecure attachment. In this study we compared the effects of an equine-assisted intervention with a conventional play-based intervention for mother-child dyads with insecure attachment, insecure caregiving and child dysregulation. Twenty mother-child dyads (with infants 12-24 months of age), with at least one part of the dyad showing an insecure attachment, were randomly assigned to eight weekly sessions of either equine-assisted or play-based intervention. Effects on mothers’ caregiving behavior and physiology and on the relationship between clients and therapists were assessed via behavior coding, salivary cortisol, heart rate and heart rate variability measures. Mothers and their infants in the equine-assisted intervention had more body contact with each other (p ≤ 0.001), a trend toward more vocal exchange (p = 0.083), and mothers showed a higher sympathetic activation, indicated by a higher heart rate (p = 0.003). In the play-based intervention, mothers showed greater parasympathetic activation than in the horse group, indicated by higher heart rate variability (p = 0.004) as well as enhanced rapport between mothers and the therapist (p = 0.016). We conclude that the main effect of the horse-assisted method was increasing positive arousal by the mother and child doing something exciting together, thus triggering attentiveness towards the child, indicated by higher rates of caregiving behavior, such as proximity and vocal contact. In contrast, the play-based intervention promoted a relaxed environment which allowed the therapists and mothers to engage more with each other. Hence, depending on intervention goals, a combination of equine-assisted and play-based interventions might be an optimal approach.

BackgroundCitizen science has evolved over the past decades by motivating members of the public to interact with scientists and actively participate in scientific research and monitoring. For this purpose, a proficient communication is mandatory in order to efficiently convey messages and reduce the gap of knowledge between scientists and lay people. In the present study, we aimed at evaluating the multiplying effect of children, who were trained to communicate their knowledge on an endangered bird species in order to engage the local community in the long-term ornithological monitoring of the free flying and individually marked colony of northern bald ibis (NBI,Geronticus eremita), which was established at the research station in 1997.MethodsPupils of the local primary schools were in regular contact with researchers, enjoyed outdoor encounters with the birds, and were invited to talk about their experience with as many people as possible. Later on, they acted as surveyors to assess the knowledge of the public on (i) the general knowledge about the species, (ii) specific knowledge about the local colony, and (iii) attitudes towards science. In two different years of evaluation (2012 and 2016) a total number of 387 persons were surveyed. The questions were generated together with the pupils and their teachers and the questionnaires were similar for both years of evaluation. All queries were in a closed format.ResultsOur results show an increase in the proportion of correct answers provided by the surveyed persons between the two years of evaluation. Education-based activities may encourage children to effectively act as multipliers of information and attitudes. This has the potential to induce sustainable changes with respect to attitude towards science, at least among local communities. Furthermore, the study suggests caution with the quality of some information reported by citizen scientists, which might be solved by more careful training actions and more specific information about local particularities. Even though the study would have gained more informative power with some additional precautions than in its current form, our findings recommend the empowerment of pupils as multipliers of scientific knowledge.

National audience; Le bien-être animal est fortement influencé par les caractéristiques du milieu de vie. Chez un certain nombre d'espèces, l'enrichissement de l'environnement du jeune animal affecte son développement comportemental et permet ainsi d'augmenter sa capacité d'adaptation au milieu et en conséquence, son bien-être. Les conditions de vie maternelles peuvent également influencer le phénotype comportemental des descendants via des effets prénatals. Ces influences maternelles apparaissent être des mécanismes adaptatifs importants en milieu naturel, préparant le jeune à son environnement postnatal. Mais ces influences maternelles peuvent également devenir des outils majeurs pour favoriser le bien-être des animaux d'élevage ou captifs. Dans ce contexte, notre étude s'est intéressée, chez la caille, aux effets des conditions de vie des femelles pondeuses sur le développement comportemental de leurs descendants. Pour cela, pendant 5 semaines, 10 femelles pondeuses sont placées en cage enrichie (présence de perchoir / pondoir ; substrat pour l'exploration et le bain de poussière) et 10 autres en cage standard. Les caractéristiques des oeufs produits et le phénotype comportemental des descendants sont ensuite comparés selon les conditions de vie maternelles. Après le traitement, les femelles en cage enrichie deviennent plus lourdes que les femelles en cage standard et produisent des oeufs contenant proportionnellement plus de vitellus et moins d'albumen. Le contenu hormonal des oeufs ne diffère cependant pas entre les deux lots. Les descendants des femelles en cage enrichie sont plus lourds et deviennent plus rapidement mâtures sexuellement que ceux des femelles en cage standard. De plus, ils expriment une plus faible réactivité émotionnelle en situation stressante et une plus forte motivation sociale. Ainsi, l'enrichissement du milieu de vie des femelles a affecté le développement morpho-physiologique et comportemental des descendants, probablement via une modulation des caractéristiques de l'oeuf. Ainsi, l'enrichissement du milieu de vie peut non seulement affecter les comportements de l'animal mais également affecter sa descendance, ceci pouvant être un outil d'amélioration du bien-être animal sur plusieurs générations.

Companion animal-directed speech (CADS) has previously been investigated in comparison to infant-directed speech and adult-directed speech. To investigate the influence of owner caregiving, attachment pattern, and personality on CADS, we used the Ainsworth strange situation procedure. It allowed us to assess voice source parameters of CADS across different contexts. We extracted speech parameters (voicing duration, voice pitch, pitch range, and jitter) from 53 dog owners recorded during the procedure. We found that owner personality and gender but not caregiving/attachment behavior affect their voice&rsquo, s pitch, range, and jitter during CADS. Further, we found a differential and context-specific modification of pitch and range, consistent with the idea that pitch communicates affect, whereas range is more of an attention-getting device. This differential usage, and the increased pitch, emphasize and support the parallels described between CADS and infant-directed speech. For the first time, we also show the effect of personality on CADS and lay the basis for including jitter as a potentially useful measure in CADS.

The relationship between brain size and ageing is a paradox. The cognitive benefits of large brains should protect from extrinsic mortality and thus indirectly select for slower ageing. However, the substantial energetic cost of neural tissue may also impact the energetic budget of large-brained organisms, causing less investment in somatic maintenance and thereby faster ageing. While the positive association between brain size and survival in the wild is well established, no studies exist on the direct effects of brain size on ageing. Here we test how brain size influences intrinsic ageing in guppy ( Poecilia reticulata) brain size selection lines with 12% difference in relative brain size. Measuring survival under benign conditions, we find that large-brained animals live 22% shorter than small-brained animals and the effect is similar in both males and females. Our results suggest a trade-off between investment into brain size and somatic maintenance. This implies that the link between brain size and ageing is contingent on the mechanism of mortality, and selection for positive correlations between brain size and ageing should occur mainly under cognition-driven survival benefits from increased brain size. We show that accelerated ageing can be a cost of evolving a larger brain.

Brain size differs substantially among species, and several hypotheses have been proposed to explain the evolution of brain size. Because the brain is among the most energetically expensive organs in the vertebrate body, trade-offs have been hypothesized to exert constraints on brain size evolution. Prominently, the expensive tissue hypothesis (ETH) proposes that reducing the size of another expensive organ, such as the gut, should compensate for the cost of a large brain. But energetic constraints may also drive covariation between the brain and other costly traits-such as body maintenance, locomotion, or reproduction-as formulated in the energy trade-off hypothesis. To date, these hypotheses have mainly been tested in homeothermic animals and within the ectothermic animals, primarily in fishes. Here, we undertake a comparative test of the interplay between energetic limitations and brain size evolution within amphibians. After controlling for phylogenetic relationships and body size, we find a negative correlation between brain mass and the length of the digestive tract within 30 species of anurans. We further find that the evolution of large brain size is accompanied by an increase in female reproductive investment into egg size. Our results suggest that the evolution of brain size follows general patterns across vertebrate clades.

Natural selection is a major force in the evolution of vertebrate brain size, but the role of sexual selection in brain size evolution remains enigmatic. At least two opposing schools of thought predict a relationship between sexual selection and brain size. Sexual selection should facilitate the evolution of larger brains because better cognitive abilities may aid the competition for mates. However, it may also restrict brain size evolution due to energetic trade‐offs between brain tissue and sexually selected traits. Here, we examined the patterns of selection on brain size and brain anatomy in male anurans (frogs and toads), a group where the strength of sexual selection differs markedly among species, using a phylogenetically controlled generalized least‐squared (PGLS) regression analyses. The analysis revealed that in 43 Chinese anuran species, neither mating system, nor type of courtship, or testes mass was significantly associated with relative brain size. While none of those factors related to the relative size of olfactory nerves, optic tecta, telencephalon, and cerebellum, the olfactory bulbs were relatively larger in monogamous species and those using calls during courtship. Our findings support the mosaic model of brain evolution and suggest that while the investigated aspects of sexual selection do not seem to play a prominent role in the evolution of brain size of anurans, they do impact their brain anatomy.

Brain size is strongly associated with body size in all vertebrates. This relationship has been hypothesized to be an important constraint on adaptive brain size evolution. The essential assumption behind this idea is that static (i.e., within species) brain-body allometry has low ability to evolve. However, recent studies have reported mixed support for this view. Here, we examine brain-body static allometry in Lake Tanganyika cichlids using a phylogenetic comparative framework. We found considerable variation in the static allometric intercept, which explained the majority of variation in absolute and relative brain size. In contrast, the slope of the brain-body static allometry had relatively low variation, which explained less variation in absolute and relative brain size compared to the intercept and body size. Further examination of the tempo and mode of evolution of static allometric parameters confirmed these observations. Moreover, the estimated evolutionary parameters indicate that the limited observed variation in the static allometric slope could be a result of strong stabilizing selection. Overall, our findings suggest that the brain-body static allometric slope may represent an evolutionary constraint in Lake Tanganyika cichlids.

Living in groups has various advantages and disadvantages for group members. We investigated the fitness consequences of early social connectivity (normalized Freeman degrees based on nearest neighbour data), physiology (levels of excreted corticosterone metabolites assayed from droppings), and agonistic interactions in a group of free-ranging greylag geese (Anseranser). Forty-four greylag geese below 3 years of age were observed in three different seasonal phases: during the re-aggregation of the flock in autumn, at the end of the winter and during the forthcoming breeding season. We show that corticosterone metabolite levels and initiated and received aggression increased with increasing social connectivity. Individuals had higher connectivity scores in the winter flock than during the mating and breeding seasons. One-year old juveniles were more connected than 2- and 3-year old individuals. In addition, we examined the link between social connectivity during early development and reproductive success several years later. We found that birds with greater connectivity early in life attempted to breed at a younger age. Furthermore, successful breeders with higher early connectivity scores had higher numbers of fledged goslings. Our results show that social context in early life stages may have long-term effects on individual fitness.

Reproductive success in monogamous species is generally affected by both behavioural and hormonal fine-tuning between pair partners. Vigilance, defence and brooding of offspring are among the main parental investments, and often the sexes adopt different roles. In the present study, we investigate how sex differences in parental behaviour and family proximity in the socially monogamous Greylag Goose (Anser anser) affect gosling survival. During the reproductive season in spring 2013, we recorded the behaviour of 18 pairs with offspring and gosling survival in a semi-tame, long-term monitored, and individually marked flock of Greylag Geese in Grünau, Austria. We found that behavioural role differentiation between the parents varied with developmental phase, and thus with gosling age. Especially during the first 10 days after hatching, females were foraging more frequently than males, which were more vigilant and aggressive towards other flock members. Such differences between the sexes levelled out 20 to 30 days after hatching. In general, females stayed in closer proximity to their offspring than males. Gosling survival was high when the parents were relatively aggressive and emphasized vigilance rather than foraging behaviour. Hence, we show a direct link between pair partners’ quality of parental investment and gosling survival. Publisher PDF

Northern Bald Ibis are socially monogamous and year-round colonial birds with a moderate repertoire of calls. Their 'croop', for example, is used during greeting of mates, but also during agonistic encounters, and provides an ideal case to study whether calls are revealing with respect to motivational states. We recorded croop calls in a semi-tame and free-roaming flock of Northern Bald Ibis in Austria, and analysed the vocal structure to identify parameters (e.g. call duration, fundamental frequency) potentially differing between social contexts, sexes and individuals. Additionally, we conducted playback experiments to test whether mated pairs would discriminate each other by their greeting croops. Acoustic features showed highly variable temporal and structural parameters. Almost all calls could be classified correctly and assigned to the different social contexts and sexes. Classification results of greeting croops were less clear for individuality. However, incubating individuals looked up more often and longer in response to playbacks of the greeting calls of their mate than to other colony members, indicating mate recognition. We show that acoustic parameters of agonistic and greeting croops contain features that may indicate the expression of affective states, and that greeting croops encode individual differences that are sufficient for individual recognition.

Despite the common assumption that the brain is malleable to surrounding conditions mainly during ontogeny, plastic neural changes can occur also in adulthood. One of the driving forces responsible for alterations in brain morphology is increasing environmental complexity that may demand enhanced cognitive abilities (e.g. attention, memory and learning). However, studies looking at the relationship between brain morphology and learning are scarce. Here, we tested the effects of both learning and environmental enrichment on neural plasticity in guppies (

Despite the common assumption that the brain is mainly malleable to surrounding conditions during ontogeny, plastic neural changes can occur also in adulthood. One of the driving forces responsible for alterations in brain morphology is increasing environmental complexity that may demand for enhanced cognitive abilities (e.g. attention, memory and learning). However, studies looking at the relationship between brain morphology and learning are scarce. Here, we tested the effects of both learning and environmental enrichment on neural plasticity in guppies (Poecilia reticulata), by means of either a reversal-learning test or a spatial-learning test. Given considerable evidence supporting environmentally-induced plastic alterations, two separate control groups that were not subjected to any cognitive test were included to account for potential changes induced by the experimental setup alone. We did not find any effect of learning on any of our brain measurements. However, we found strong evidence for an environmental effect, where fish given access to the spatial-learning environment had larger relative brain size and optic tectum size in relation to those exposed to the reversal-learning environment. Our results demonstrate the plasticity of the adult brain to respond adaptively mainly to environmental conditions, providing support for the environmental enhancement theory.

Neurons are the basic computational units of the brain, but brain size is the predominant surrogate measure of brain functional capacity in comparative and cognitive neuroscience. This approach is based on the assumption that larger brains harbor higher numbers of neurons and their connections, and therefore have a higher information‐processing capacity. However, recent studies have shown that brain mass may be less strongly correlated with neuron counts than previously thought. Till now, no experimental test has been conducted to examine the relationship between evolutionary changes in brain size and the number of brain neurons. Here, we provide such a test by comparing neuron number in artificial selection lines of female guppies (Poecilia reticulata) with >15% difference in relative brain mass and numerous previously demonstrated cognitive differences. Using the isotropic fractionator, we demonstrate that large‐brained females have a higher overall number of neurons than small‐brained females, but similar neuronal densities. Importantly, this difference holds also for the telencephalon, a key region for cognition. Our study provides the first direct experimental evidence that selection for brain mass leads to matching changes in number of neurons and shows that brain size evolution is intimately linked to the evolution of neuron number and cognition.

We published a study recently testing the link between brain size and behavioural plasticity using brain size selected guppy (Poecilia reticulata) lines (2019, Journal of Evolutionary Biology, 32, 218-226). Only large-brained fish showed habituation to a new, but actually harmless environment perceived as risky, by increasing movement activity over the 20-day observation period. We concluded that "Our results suggest that brain size likely explains some of the variation in behavioural plasticity found at the intraspecific level". In a commentary published in the same journal, Haave-Audet et al. challenged the main message of our study, stating that (a) relative brain size is not a suitable proxy for cognitive ability and (b) habituation measured by us is likely not adaptive and costly. In our response, we first show that a decade's work has proven repeatedly that relative brain size is indeed positively linked to cognitive performance in our model system. Second, we discuss how switching from stressed to unstressed behaviour in stressful situations without real risk is likely adaptive. Finally, we point out that the main cost of behavioural plasticity in our case is the development and maintenance of the neural system needed for information processing, and not the expression of plasticity. We hope that our discussion with Haave-Audet et al. helps clarifying some central issues in this emerging research field.

Supplementary material

International audience; Animal welfare is strongly influenced by characteristics of the animals' environment. Thus, enrichment of Mammals' and Birds' environments at early age modulates their behavioural development and can increase their ability to cope with their milieu, consequently improving the animals' welfare. However, individual behavioural development is strongly affected prenatally by maternal living conditions. Many authors consider these prenatal maternal effects to be prenatal adaptive mechanisms preparing offspring for their postnatal environment. In this context, our study investigated the effects of environmental enrichment (via foraging and structural enrichments) of laying Japanese quail females’ living conditions on their offspring’s general development. For that, 10 laying quail were kept in enriched cages (EC females) for 5 weeks and characteristics of their eggs and chicks were compared to those of 10 females housed in standard cage (SC females). After the treatment, EC females were heavier than SC females and produced eggs containing proportionally more yolk and less albumen than those of SC females. However, levels of egg hormonal contents (testosterone, androstenedione, progesterone) did not differ significantly between the two groups. Chicks of EC females (EC chicks) were globally heavier than chicks of SC females (SC chicks) from hatching to 5 weeks old and their sexual development was more precocious than that of SC chicks. Moreover, emotional reactivity of EC chicks, in behavioural tests, was lower and their social motivation was higher than that of SC chicks. So, our study shows that enrichment of laying females’ environment modulates their offspring’s morphological and behavioural development, probably in relation to characteristics of the eggs. Controlling prenatal maternal effects could be a way to improve animal welfare over several generations.

This exploratory study describes the development of a classification system for dogs’ attachment security to caregivers that adheres closely to Ainsworth’s seminal methodology. Fifty-nine adult dogs and caregivers participated in a mildly threatening laboratory encounter with a stranger (TS) and the Strange Situation (SSP). Dog and attachment experts adapted Ainsworth’s classification system for the behavioral repertoire of the dog. Four potentially comparable patterns of attachment were identified. The proportions of secure and insecure classifications (61% and 39%) were similar to those found in human toddlers. Caregivers’ sensitivity to their dogs during the TS procedure significantly differentiated dogs with secure vs. insecure classifications Lower scores on the Active/excited personality scale on the Monash Canine Personality Questionnaire-Revised (MCPQ-R) also were related to secure classification. This system now makes it possible to compare directly the effects of human and dog attachment patterns on the health and emotional well-being of humans and dogs.

Understanding how animal personality (consistent between-individual behavioural differences) arises has become a central topic in behavioural sciences. This endeavour is complicated by the fact that not only the mean behaviour of individuals (behavioural type) but also the strength of their reaction to environmental change (behavioural plasticity) varies consistently. Personality and cognitive abilities are linked, and we suggest that behavioural plasticity could also be explained by differences in brain size (a proxy for cognitive abilities), since accurate decisions are likely essential to make behavioural plasticity beneficial. We test this idea in guppies (Poecilia reticulata), artificially selected for large and small brain size, which show clear cognitive differences between selection lines. To test whether those lines differed in behavioural plasticity, we reared them in groups in structurally enriched environments and then placed adults individually into empty tanks, where we presented them daily with visual predator cues and monitored their behaviour for 20 days with video-aided motion tracking. We found that individuals differed consistently in activity and risk-taking, as well as in behavioural plasticity. In activity, only the large-brained lines demonstrated habituation (increased activity) to the new environment, whereas in risk-taking, we found sensitization (decreased risk-taking) in both brain size lines. We conclude that brain size, potentially via increasing cognitive abilities, may increase behavioural plasticity, which in turn can improve habituation to novel environments. However, the effects seem to be behaviour-specific. Our results suggest that brain size likely explains some of the variation in behavioural plasticity found at the intraspecific level.

Animals living in groups can show substantial variation in social traits and this affects their social organization. However, as the specific mechanisms driving this organization are difficult to identify in already organized groups typically found in the wild, the contribution of interindividual variation to group level behaviour remains enigmatic. Here, we present results of an experiment to create and compare groups that vary in social organization, and study how individual behaviour varies between these groups. We iteratively sorted individuals between groups of guppies, Poecilia reticulata, by ranking the groups according to their directional alignment and then mixing similar groups. Over the rounds of sorting the consistency of the group rankings increased, producing groups that varied significantly in key social behaviours such as collective activity and group cohesion. The repeatability of the underlying individual behaviour was then estimated by comparing the experimental data to simulations. At the level of basic locomotion, individuals in more coordinated groups displayed stronger interactions with the centre of the group, and weaker interactions with their nearest neighbours. We propose that this provides the basis for a passive phenotypic assortment mechanism that may explain the structures of social networks in the wild.

Puppy packs (consisting of only puppies) and mixed-age packs (composed of puppies and adults) were observed to test whether social play can be used for assessing and establishing social relations in wolves, Canis lupus. Differently from previous studies, we looked at play behaviours in detail, allowing us to categorize play interactions as either competitive or relaxed, and predicted that different types of play would be associated with different relationships between individuals. We found that the more time dyads spent in relaxed play, the more affiliative interactions they exchanged outside of play. In the mixed-age packs, dyads that spent more time in both relaxed and competitive play showed fewer exchanges of aggressive behaviours. Conversely, in puppy packs, the more time dyads spent in competitive play, the more aggressive interactions were exchanged outside of play. Since clear dominance relationships emerged in the mixed-age packs, but not in puppy packs, we suggest that play can help to reduce the frequency of aggressive interactions only when a clear hierarchy exists between pack members. Furthermore, we found that in both puppy and mixed-age packs, dominance relationships were reflected and rarely reversed during play. Finally, dyads with a less clear dominance relationship spent more time playing in a competitive way. Overall, our results support the social assessment hypothesis suggesting that social relationships outside of play are reflected during playful interactions. Moreover, we revealed how different types of play, that is, playing in a competitive or relaxed way, may be related to different social relationships. This distinction between play types has not been acknowledged before but could help researchers better understand the functions of play in different species., Highlights • Wolves may use play to establish and assess social relationships. • Play behaviour is correlated with both affiliative and dominance relationships. • Play may reduce the rate of aggressions when a clear hierarchy exists in the pack. • Different types of play may be related to different social relationships.

Variation in resting behaviour across animals may be driven by adaptations towards their environment. Wolves and dogs seem promising models to examine this idea as they share a common ancestor, but occupy different socio-ecological niches. While wolves generally avoid humans, hunt, defend their territory, and raise offspring cooperatively, most dogs live in human-shaped environments. Hence, we hypothesized wolves to be more alert towards their environment than dogs, i.e. the degree of activation along the sleep-wake continuum (alertness) should be greater in wolves than in dogs. We estimated alertness via cardiac output. We tested similarly raised and kept pack-living wolves and dogs in two different behavioural conditions: (1) inactive wakefulness: animal is lying, head in an upward position with eyes opened, (2) resting: animal is lying, head in downward position with eyes mainly closed. In contrast to our expectations, we found that in both conditions wolves had a lower heart rate and higher heart rate variability than dogs, i.e. wolves might be less alert/more relaxed than dogs. Although our results are preliminary, we suggest that the higher alertness of dogs compared to wolves is potentially driven by differences in their socio-ecology (i.e. domestication) causing greater attention of dogs to human behaviour.

Reproductive success in monogamous species is generally affected by both behavioural and hormonal fine-tuning between pair partners. Vigilance, defence and brooding of offspring are among the main parental investments, and often the sexes adopt different roles. In the present study, we investigate how sex differences in parental behaviour and family proximity in the socially monogamous Greylag Goose (Anser anser) affect gosling survival. During the reproductive season in spring 2013, we recorded the behaviour of 18 pairs with offspring and gosling survival in a semi-tame, long-term monitored, and individually marked flock of Greylag Geese in Grünau, Austria. We found that behavioural role differentiation between the parents varied with developmental phase, and thus with gosling age. Especially during the first 10 days after hatching, females were foraging more frequently than males, which were more vigilant and aggressive towards other flock members. Such differences between the sexes levelled out 20 to 30 days after hatching. In general, females stayed in closer proximity to their offspring than males. Gosling survival was high when the parents were relatively aggressive and emphasized vigilance rather than foraging behaviour. Hence, we show a direct link between pair partners’ quality of parental investment and gosling survival. Electronic supplementary material The online version of this article (10.1007/s10336-019-01638-x) contains supplementary material, which is available to authorized users.

A wealth of recent behavioral, neurobiological, and genetic results allows us to draw a new, comprehensive picture of the human-wolf- dog relationship. Dogs originated from wolves 35,000 years ago, mainly via selection for tameness. Wolves were probably spiritual partners and hunting buddies of Paleolithic hunter-gatherers over wide areas of Eurasia. Coming together and staying together was probably facilitated by the close ecological and social match between wolves and humans. Both are cursorial hunters and scavengers living in cooperative but relatively closed family groups, which selected for very similar mentalities. Parallel selection for tameness (i.e., being “nice”) in dogs and humans quickly and in a diverse way changed behavioral and anatomical phenotypes from wolf to dog, and social orientation from Stone Age to modern humans. Actually, dogs were the most important human companions in conquering the world. By adapting to the needs of diverse human societies and civilizations, a wide variety of dogs developed. Over long periods of history dogs were meant to be benign with their own humans, but not with strangers. Hence human ingroup-outgroup distinctions may explain why considerable aggressiveness may still be found in dogs and humans, although incompatible today with a globalized world and universal ethics. In dogs this can be easily controlled by selective breeding and in humans, less easily, by cognition. Actually, sledge dogs and modern hunting breeds were selected for tolerance in the past. Most recent scientific results not only underline how closely dogs match human operational and social needs, but also find that most of the dog’s social behavior, cognition, and cooperativeness is direct wolf heritage and did not emerge in domestication, as previously thought. Dogs have adjusted to human needs in many subtle ways in the course of domestication. This makes dogs much better companions than tame wolves. Dogs are more easily socialized; they are strongly tuned toward people, respect human leadership, and are superior receivers and donors of emotional social support. Dogs actually became more obedient and respectful of social hierarchies than wolves, more dependent on human support, and better at inhibiting their impulses. Dogs diversified their barking for communicating with humans. They can read our emotions and adjust to them in an empathic way. Dogs are capable of human-like thinking, of taking a human perspective, and even of tricking us. Not least, they share a sense of fairness with wolves and humans. Hence, dogs can be particularly valuable partners in meeting universal human social needs. Human-dog relationships are “essentialized,” lacking the cultural and symbolic complexities of relationships between humans. But the devotion of dogs is not unconditional; they do judge our moods and social conduct and make their choices accordingly. Dogs can boost the self-esteem and agency of their human partners and are excellent “social lubricants,” thereby connecting people. Actually, in their flexibility, social devotion, adaptiveness, and responsiveness, dogs are the stars among all animal companions. No wonder, as the human-dog relationship started in the early Paleolithic, tens of thousands of years before the domestication of other animals. Dog companionship seems increasingly important in a globalized and digitalized world. An ever accelerating pace of life may not always provide the conditions needed to keep people physically and mentally healthy. Living in good relationships with dogs can keep people connected with their social essentials. Therefore, dogs are prime animal assistants in a wide range of activities, pedagogy, and therapy. Supported by human biophilia, the presence of a friendly dog may have strong calming and socializing effects on humans and may support communication and sociopositive behavior. Dogs are probably the most socially responsive of all companion animals, privately and in professional settings. In all such activities (for definitions please see the White Paper of the International Association of Human-Animal Interaction Organizations [IAHAIO], Jegatheesan et al., 2014), well-socialized and friendly dogs respond well to temporary and positive challenges, but must never be overburdened. It requires a suitable dog in a secure relationship with a sensitive and knowledgeable human partner. Furthermore, it has to be kept in mind that dog partners need regular veterinarian checks in the interest of the animals’ health and welfare and to minimize health risks (e.g., zoonoses) for the human partners. All activities and work need to conform to the IAHAIO Guidelines for Animal-Assisted Activities and Animal-Assisted Therapy (Prague, 1998) and with the IAHAIO White Paper (Jegatheesan et al., 2014).

BackgroundBrain size is expected to evolve by a balance between cognitive benefits and energetic costs. Several influential hypotheses have suggested that large brains may be especially beneficial in social contexts. Group living and competition may pose unique cognitive challenges to individuals and favor the evolution of increased cognitive ability. Evidence comes from comparative studies on the link between social complexity and brain morphology, but the strength of empirical support has recently been challenged. In addition, the behavioral mechanisms that would link cognitive ability to sociality are rarely studied. Here we take an alternative approach and investigate experimentally how brain size can relate to the social competence of individuals within species, a problem that so far has remained unresolved. We use the unique guppy brain size selection line model system to evaluate whether large brains are advantageous by allowing individuals to better assess their performance in a social contest situation. Based on theoretical literature, we predict that contest duration should depend on the brain size of the loser, as it is the capitulation of the losing individual that ends the fight.ResultsFirst, we show that studying the movement of competitors during contests allows for precise estimation of the dominance timeline in guppies, even when overt aggression is typically one-sided and delayed. Second, we staged contests between pairs of male that had been artificially selected for large and small relative brain size, with demonstrated differences in cognitive ability. We show that dominance was established much earlier in contests with large-brained losers, whereas the brain size of the winner had no effect. Following our prediction, large-brained individuals gave up more quickly when they were going to lose.ConclusionsThese results suggest that large-brained individuals assess their performance in contests better and that social competence indeed can depend on brain size. Conflict resolution may therefore be an important behavioral mechanism behind macro-evolutionary patterns between sociality and brain size. Since conflict is ubiquitous among group-living animals, the possible effects of the social environment on the evolution of cognition may be more broadly applicable than previously thought.