A review of the unsolvable task in dog communication and cognition: comparing different methodologies.

Communication between dogs and humans is a topic of growing interest, and the "unsolvable task" is a common method used to measure human-directed communication. In this task, dogs learn how to solve a problem to obtain a reward. After a fixed number of trials, the reward becomes impossible to access, arguably leading to communicative attempts from the dog. Although useful to observe dogs' communicative behaviors in a fairly naturalistic situation, the methodology varies among studies regarding apparatus, number of trials, and other factors. The proxies used, for instance, gaze duration or frequency of gaze alternation, also vary, and there are discrepancies and a debate regarding what the task actually measures. Therefore, in this study, we reviewed the usage of the unsolvable task in canids of the genus Canis, searching Web of Science and Scopus for the terms "dog*", "Canis", "dingo*", "wolf" or "wolves" in the title and "unsolvable task" or "impossible task" in the topic. We included thirty-five studies in this review and discussed their different methodologies and proxies, such as different apparatuses, number of solvable trials, and different interpretations of "looking back", pointing out how they can affect results and hinder comparisons. Lastly, we used current data to propose strategies to homogenize the use of this important paradigm, with an ethogram of possible behaviors and their interpretation and a predefined set of methodological aspects for future research.

Dogs recognize dog and human emotions.

The perception of emotional expressions allows animals to evaluate the social intentions and motivations of each other. This usually takes place within species; however, in the case of domestic dogs, it might be advantageous to recognize the emotions of humans as well as other dogs. In this sense, the combination of visual and auditory cues to categorize others' emotions facilitates the information processing and indicates high-level cognitive representations. Using a cross-modal preferential looking paradigm, we presented dogs with either human or dog faces with different emotional valences (happy/playful versus angry/aggressive) paired with a single vocalization from the same individual with either a positive or negative valence or Brownian noise. Dogs looked significantly longer at the face whose expression was congruent to the valence of vocalization, for both conspecifics and heterospecifics, an ability previously known only in humans. These results demonstrate that dogs can extract and integrate bimodal sensory emotional information, and discriminate between positive and negative emotions from both humans and dogs.

Erratum: The shape of lipsmacking: socio-emotional regulation in bearded capuchin monkeys (Sapajus libidinosus) - CORRIGENDUM.

[This corrects the article DOI: 10.1017/ehs.2023.10.].

The shape of lipsmacking: socio-emotional regulation in bearded capuchin monkeys (Sapajus libidinosus).

Capuchin monkeys have rich social relationships and from very young ages they participate in complex interactions with members of their group. Lipsmacking behaviour, which involves at least two individuals in socially mediated interactions, may tell about processes that maintain, accentuate or attenuate emotional exchanges in monkeys. Lipsmacking is a facial expression associated with the establishment and maintenance of affiliative interactions, following under the 'emotional regulation' umbrella, which accounts for the ability to manage behavioural responses. We investigated behaviours related to the emitter and to the receiver (infant) of lipsmacking to answer the question of how lipsmacking occurs. In capuchin monkeys, lipsmacking has been previously understood solely as a face-to-face interaction. Our data show that emitters are engaged with infants, looking longer towards their face and seeking eye contact during the display. However, receivers spend most of the time looking away from the emitter and stay in no contact for nearly half of the time. From naturalistic observations of wild infant capuchin monkeys from Brazil we found that lipsmacking is not restricted to mutual gaze, meaning there are other mechanisms in place than previously known. Our results open paths to new insights about the evolution of socio-emotional displays in primates.

Size, skull shape and age influence the temperament of domestic dogs.

Studies have investigated the relationship between dogs' morphological characteristics and behavioural dimensions, but little is discussed about this relationship in the context of dogs' responses to emotion eliciting stimuli and temperament. Based on the assumption that the developmental trajectory of behaviour and emotion processing is impacted by the interaction between organisms and environment, we analysed whether dogs' characteristics - that determine how they perceive and interact with their surroundings - affect temperament profiles. We looked at size, height, weight, skull morphology, age, sex, reproductive status, and breed of a sample of Brazilian domestic dogs' and their temperament (measured as Positive and Negative Activation), obtained via the PANAS questionnaire for dogs. We tested possible main effects and first-order interactions in linear mixed models. Younger dogs showed higher positive activation (i.e. sensitivity to positive stimuli; play and treats). For short snouted dogs, the older the dog, less was the negative activation (i.e. sensitivity to negative stimuli; punishment). And for long snouted dogs, larger dogs showed lower negative activation. Weight alone also showed an effect, with heavier dogs having less sensitivity to negative stimuli. Overall, our study demonstrated how morphology and age are important factors that influence temperament expression and emotional reactivity in dogs.

Obese Vegetarians and Omnivores Show Different Metabolic Changes: Analysis of 1340 Individuals.

Our study evaluated the association between the increase in body mass index (BMI) in men and women (menstruating and non-menstruating) (n = 1340) with different dietary groups (omnivores, semi-vegetarians, lacto-ovo-vegetarian, and vegans) and the measurement of the biochemical markers high-sensitive C-reactive protein (hs-CRP), ferritin, alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyl transferase (GGT), glycated hemoglobin (HbA1C), and insulin resistance index (HOMA-IR). Increasing BMI values in all groups and dietary profiles were related to a significant increase in hs-CRP (p < 0.0001), ALT (p = 0.02), ferritin (p = 0.009), and HbA1C (p < 0.0001), with no difference between dietary groups (p < 0.05). The increase in BMI increases the levels of HOMA-IR (p < 0.0001) and GGT (p < 0.05), with higher values found in men when compared to women (p < 0.0001 for HOMA- IR and p = 0.0048 for GGT). The association between ALT and BMI was different between dietary groups, as it showed a decrease in vegan women who do not menstruate compared to other dietary groups (p = 0.0099). When including only obese individuals (BMI ≥ 30 kg/m2, n = 153) in the analysis, we observed lower concentrations of GGT and ferritin in vegetarians than in omnivores, regardless of gender and menstrual blood loss (p = 0.0395). Our data showed that for both vegetarians and omnivores, the higher the BMI, the worse the metabolic parameters. However, regarding obesity, vegetarians showed better antioxidant status (lower GGT elevation) and lower inflammatory status (lower ferritin elevation), which may provide them with potential protection in the development of morbidities associated with overweight.

Do Emotional Cues Influence the Performance of Domestic Dogs in an Observational Learning Task?

Using social information is not indiscriminate and being able to choose what to copy and from whom to copy is critical. Dogs are able to learn socially, to recognize, and respond to dog as well as human emotional expressions, and to make reputation-like inferences based on how people behave towards their owner. Yet, the mechanisms dogs use for obtaining and utilizing social information are still to be fully understood, especially concerning whether emotional cues influence dogs' social learning. Therefore, our main aim was to test the hypothesis that an emotionally charged (negative, positive, or neutral) interaction with the demonstrator of a "V" detour task prior to testing would affect subjects' performance, by: (i) changing the value of the information provided by the demonstrator or (ii) changing the valence of the learning environment. Our experimental design consisted of three phases: pre-test (subjects were allowed to solve the task alone); emotional display (dogs watched the unfamiliar human behaving in either a positive, negative or neutral way towards their owner); test (demonstrator showed the task and subjects were allowed to move freely). Only dogs that failed in pre-test were considered for analysis (n = 46). We analyzed four dependent variables: success, time to solve the task, latency to reach the fence and matching the side of demonstration. For each, we used four models (GEEs and GLMMs) to investigate the effect of (1) demographic factors; (2) experimental design factors (including emotional group); (3) behavior of the dog; and (4) side chosen and matching. All models took into account all trials (random effect included) and the first trials only. Our findings corroborate previous studies of social learning, but present no evidence to sustain our hypothesis. We discuss the possibility of our stimuli not being salient enough in a task that involves highly motivating food and relies on long and highly distracting interval between phases. Nevertheless, these results represent an important contribution to the study of dog behavior and social cognition and pave the way for further investigations.

Effect of different experiences with humans in dogs' visual communication.

Dogs are particularly skillful in communicating with humans, and growing evidence points towards the importance of both species intertwined evolutionary history and intense daily partnership. Gaze alternation is a communicative behavior used by dogs from a very young age and is affected by factors such as aging and experience. We analyzed how different degrees of daily human interaction affect dogs' gazing behavior in the unsolvable task, where a desired food becomes inaccessible. Three groups with different degrees of daily exposure to humans were compared: pet dogs that live inside the house, pet dogs that live outside the house, and shelter dogs. We found no difference in latency to the first gaze, but pet dogs did show a higher proportion of individuals engaging in gaze alternation, a higher number of gaze alternations, and a longer duration of gaze than shelter dogs. Additionally, dogs living inside the house gazed more at the experimenter than dogs living outside. Overall, our results indicate a strong influence of experience over the development and use of these communicative behaviors in dogs, with groups that are closer to people in their daily lives being more willing to communicate with humans as a strategy to obtain a desired goal.

Iron Deficiency in Vegetarian and Omnivorous Individuals: Analysis of 1340 Individuals.

The objective of this study was to evaluate the serum levels of ferritin and the prevalence of iron deficiency in vegan and omnivorous individuals by taking into account the presence of elements that cause an elevation of ferritin levels, such as increased homeostatic model assessment of insulin resistance (HOMA-IR), body mass index (BMI), and high-sensitivity C-reactive protein (hs-CRP) values. The parameters were evaluated in 1340 individuals, i.e., 422 men and 225 women who do not menstruate and 693 women who do menstruate, based on omnivorous or vegetarian eating habits. The progressive increase in BMI, HOMA-IR, and inflammation caused an elevation in ferritin concentration, regardless of the eating habits in the groups studied. In the overall sample, omnivores had a higher prevalence of obesity, higher ferritin levels, and a lower prevalence of iron deficiency (ferritin < 30 ng/mL). However, after the exclusion of individuals with inflammation (with overweight/obesity and elevated hs-CRP levels), the actual iron deficiency was assessed and was not higher among vegetarians, except in women with regular menstrual cycles. Our data show that nutritional status and inflammation levels affect ferritin levels and may interfere with the correct diagnosis of iron deficiency in both vegetarian and omnivorous individuals. Compared to vegetarians, women who do not menstruate and men had the same prevalence of iron deficiency when following an omnivorous diet.

Mood changes in the course of preparation for the Brazilian university admission exam - a longitudinal study.

OBJECTIVE: Academic examinations are an important source of stress for students. This study is intended to assess senior high school students' mood changes during the preparation for a very important academic examination, the Brazilian university admission examination. METHOD: Positive and Negative Affect Schedule - Expanded Form was used to assess the students three times in the course of the months preceding the examination. RESULTS: ANOVA for repeated measures showed that Negative Affect increased as the examination approached, and that this increment was already present months before the examination took place. A single conditionally independent random effect model showed that time spent studying was associated with fluctuations in mood. CONCLUSION: Teenagers, in preparation for a very important examination, may present mood disturbances associated with both the proximity of the examination and their study load months before the examination actually takes place. Other stressing factors may play a role in these findings and should be further investigated.

Demographics and self-reported well-being of Brazilian adults as a function of pet ownership: A pilot study.

The goals of the present study were to investigate socio-demographic characteristics and well-being indicators associated with pet ownership. The respondents (N = 801, 53.8% females; 56.2% with children) came from the five macro-regions of Brazil (8% North, 28% Northeast, 36% Southeast, 18% South, 10% Central-West). Their ages ranged from 20 to 50 years. Over half of the sample (60%) reported living with a pet. Logistic regression showed that residence type (to be owner versus renter) and parental status (to be childless versus to have children) were predictors of pet ownership. We found interaction between pet ownership and sex on well-being indicators: the Mann-Whitney test showed that men who owned a pet reported better sleep quality, better relationship with neighbors and less sadness; whereas women who owned a pet reported lower life organization. With respect to life satisfaction, no differences were found between pet owners and non-pet owners. Implications of our findings and new research directions are discussed. Our study was conducted before the Covid-19 pandemic. The survey should be reapplied during and after the pandemic, so that we can deepen our knowledge of the socio-demographic characteristics and subjective well-being indicators associated with pet ownership.

Assessment of emotional predisposition in dogs using PANAS (Positive and Negative Activation Scale) and associated relationships in a sample of dogs from Brazil.

The English version of the Positive and Negative Activation Scale (PANAS) is a useful tool for the assessment of dog temperament, helping to identify highly sensitive individuals that could be at risk of developing fears, phobias and anxiety problems, and potentially depressive states. This study evaluated the association between dogs' and owners' characteristics and dog temperament in Brazil. To accomplish this, we adapted and validated a Portuguese language version of PANAS for dogs. Data from 1744 owner-dog dyads were analysed and a two-factor structure similar to the original PANAS was revealed that met the requirements for validity and internal consistency. We found that dogs owned by women, neutered dogs and those who live in single-dog households show higher negative activation. Moreover, the older the owner, the less the negative activation for dogs that are bought. We also found that the older the dog, the less the positive activation, but this score is higher in dogs that sleep inside the house. Interestingly, mixed-breed dogs scored higher for both negative and positive emotional activation compared to purebreds. These findings alongside the particular profile of dogs in Brazil, including its large population of mixed-breed, emphasise the value of cross-cultural investigations in order to develop a full understanding of dog behaviour.

Goats prefer positive human emotional facial expressions.

Domestication has shaped the physiology and the behaviour of animals to better adapt to human environments. Therefore, human facial expressions may be highly informative for animals domesticated for working closely with people, such as dogs and horses. However, it is not known whether other animals, and particularly those domesticated primarily for production, such as goats, are capable of perceiving human emotional cues. In this study, we investigated whether goats can distinguish human facial expressions when simultaneously shown two images of an unfamiliar human with different emotional valences (positive/happy or negative/angry). Both images were vertically attached to a wall on one side of a test arena, 1.3 m apart, and goats were released from the opposite side of the arena (distance of 4.0 m) and were free to explore and interact with the stimuli during the trials. Each of four test trials lasted 30 s. Overall, we found that goats preferred to interact first with happy faces, meaning that they are sensitive to human facial emotional cues. Goats interacted first, more often and for longer duration with positive faces when they were positioned on the right side. However, no preference was found when the positive faces were placed on the left side. We show that animals domesticated for production can discriminate human facial expressions with different emotional valences and prefer to interact with positive ones. Therefore, the impact of domestication on animal cognitive abilities may be more far-reaching than previously assumed.

Eye Contact Is Crucial for Referential Communication in Pet Dogs.

Dogs discriminate human direction of attention cues, such as body, gaze, head and eye orientation, in several circumstances. Eye contact particularly seems to provide information on human readiness to communicate; when there is such an ostensive cue, dogs tend to follow human communicative gestures more often. However, little is known about how such cues influence the production of communicative signals (e.g. gaze alternation and sustained gaze) in dogs. In the current study, in order to get an unreachable food, dogs needed to communicate with their owners in several conditions that differ according to the direction of owners' visual cues, namely gaze, head, eyes, and availability to make eye contact. Results provided evidence that pet dogs did not rely on details of owners' direction of visual attention. Instead, they relied on the whole combination of visual cues and especially on the owners' availability to make eye contact. Dogs increased visual communicative behaviors when they established eye contact with their owners, a different strategy compared to apes and baboons, that intensify vocalizations and gestures when human is not visually attending. The difference in strategy is possibly due to distinct status: domesticated vs wild. Results are discussed taking into account the ecological relevance of the task since pet dogs live in human environment and face similar situations on a daily basis during their lives.

Sobre a relação humano-cão / Concerning the human-dog relationship / La relation homme-chien / Sobre la relación humano-perro

Resumo Neste artigo são discutidos aspectos concernentes ao início do convívio entre cães e humanos e às diferenças culturais que afetam as relações entre as duas espécies. O estudo das interações entre humanos e cães precisa trazer à tona a pluralidade de fenômenos interconectados: o processo de domesticação iniciado há milhares de anos, os efeitos evolutivos da relação entre as duas espécies e os aspectos culturais que influenciam a convivência entre nós. Considerando essa visão holística, enxergamos de maneira ampla o cenário interacionista, estabelecendo paralelos muitas vezes ignorados por estudos pontuais e/ou enviesados por paradigmas experimentais de baixa relevância ecológica para os animais.

Abstract This article discusses the beginning of the relationship between dogs and humans and the cultural differences that affect the relationships between the two species. The study of interactions between humans and dogs needs to bring to light its plurality of interconnected phenomena: the domestication process that began thousands of years ago, the evolutionary effects of their relationship and the cultural aspects that influence such coexistence. Given this holistic view, we perceive this interaction scenario broadly, establishing parallels often ignored by one-off studies and/or biased by experimental paradigms of low ecological relevance to animals.

Résumé Dans cet article sont discutés des aspects liés au début de la cohabitation entre les chiens et les humains et les différences culturelles qui affectent ces relations interspécifiques. L'étude des interactions entre humains et chiens doit faire apparaître la pluralité des phénomènes reliés entre eux : le processus de domestication qui a commencé il y a milliers d'années, les effets évolutifs de cette relation et les aspects culturels qui influencent la coexistence entre nous. Compte tenu de cette vision holistique, c'est possible de voir largement le scénario interactionniste, et d'établir des parallèles souvent ignorés par les études individuelles ou biaisé par des paradigmes expérimentaux d'importance écologique négligeable pour les animaux.

Resumen Este artículo analiza los aspectos relacionados con el comienzo de la relación entre perros y humanos, y las diferencias culturales que afectan las relaciones entre las dos especies. El estudio de las interacciones entre humanos y perros necesita sacar a la luz la pluralidad de fenómenos interconectados: el proceso de domesticación que comenzó hace miles de años, los efectos evolutivos de la relación entre las dos especies y los aspectos culturales que influyen en la convivencia entre nosotros. Teniendo en cuenta esta visión holística, vemos el panorama interaccionista de manera general, estableciendo paralelos a menudo ignorados por estudios específicos y/o sesgados por paradigmas experimentales de baja relevancia ecológica para los animales.

In vitro evaluation of verapamil and other modulating agents in Brazilian chloroquine-resistant Plasmodium falciparum isolates.

Verapamil, was assayed to record its modulating effect upon Brazilian Plasmodium falciparum isolates resistant to chloroquine. Other cardiovascular drugs known to be modulating agents in resistant malaria and/or multidrug-resistant neoplasias, including nifedipine, nitrendipine, diltiazem and propranolol, were also evaluated. Concentrations similar to those for cardiovascular therapy were used in the in vitro microtechnique for antimalarial drug susceptibility. Intrinsic antiplasmodial activity was observed from the lowest concentrations without a significant modulating action. Other reported modulating agents, such as the antipsychotic drug trifluoperazine and the antidepressants desipramine and imipramine, demonstrated similar responses under the same experimental conditions. Results suggest a much higher susceptibility of Brazilian strains, as well as an indifferent behaviour in relation to modulating agents.

Are dogs able to communicate with their owners about a desirable food in a referential and intentional way?

The ability of dogs to use human communicative signals has been exhaustively studied. However, few studies have focused on the production of communicative signals by dogs. The current study investigated if dogs are able to communicate by using directional signals towards some desirable object in the environment and also if they show an apparent intention to manipulate their owner's behavior in order to receive it. Some operational criteria were used to investigate referential and intentional communication: the signal should be influenced by the audience and by the recipient's direction of visual attention; the sender should display gaze alternations between the recipient and the object and attention-getting behaviors, and, finally, the sender should persist and elaborate the communication when attempts to manipulate the recipient failed. Aiming to investigate these criteria in dogs, 29 subjects were tested using an experimental set up in which they could see a desirable but unreachable food and they needed the cooperation of their owners in order to receive it. This study found evidence of all operational criteria, especially for gaze alternation between the owner and the food, which suggested that some dogs' communicative behaviors could be functionally referential and intentional. Nevertheless, similar to other studies about social cognition in animals, it is not possible to distinguish if the dog's behaviors are based on simple mechanisms or on a theory of mind about their owners.

Tufted capuchin monkeys (Sapajus sp) learning how to crack nuts: does variability decline throughout development?

We investigated the process of nut-cracking acquisition in a semi-free population of tufted capuchin monkeys (Sapajus sp) in São Paulo, Brazil. We analyzed the cracking episodes from monkeys of different ages and found that variability of actions related to cracking declined. Inept movements were more frequent in juveniles, which also showed an improvement on efficient striking. The most effective behavioral sequence for cracking was more frequently used by the most experienced monkeys, which also used non-optimal sequences. Variability in behavior sequences and actions may allow adaptive changes to behavior under changing environmental conditions.

Are dogs sensitive to the human's visual perspective and signs of attention when using a keyboard with arbitrary symbols to communicate?

This study investigated whether dogs take into account the human's direction of attention and visual field when they communicate by means of a keyboard with lexigrams. In order to test this, two dogs, Sofia and Laila, were given the choice between two keyboards, one visible and the other one non-visible from the experimenter's perspective. In one experiment, different barriers were positioned in such way so as to block the experimenter's visibility to one of the keyboards, and, in another experiment we manipulated human's signs of attention, like body orientation and visibility of the eyes. Sofia and Laila consistently preferred to use the keyboard that was in the human's visual field. Laila's choice was also influenced by the human's body orientation. Results suggested that the subjects are sensitive to the human's visual access to the keyboard when they use it to ask for food.

Este estudo investigou se cães levam em conta a direção da atenção e o campo visual do ser humano quando se comunicam por meio de um teclado com lexigramas. Para tanto, duas cadelas, Sofia e Laila, foram submetidas a uma situação em que podiam escolher entre dois teclados, um deles visível e outro não-visível sob a perspectiva do experimentador. Em um experimento, diferentes barreiras foram posicionadas de tal forma a bloquear a visibilidade do experimentador a um dos teclados, e, em outro, experimento manipulamos os sinais de atenção do ser humano, como orientação corporal e visibilidade dos olhos. Sofia e Laila preferiram consistentemente usar o teclado que estava dentro do campo visual do ser humano. A escolha de Laila também foi influenciada pela orientação corporal do ser humano. Os resultados sugerem que as duas são sensíveis ao acesso visual do ser humano ao teclado quando elas o usam para pedir comida.