Prof. Joseph Levine

Senior Psychiatrist




Conversation 30: Socializing relationships in non-human mammals

By Prof. Levine & Dr. Salganik


This time we will discuss the social structures of mammals apart from those of the higher primates for which we will have a separate conversation. First, we would like to bring here a call for an empathic approach that encourages the understanding of animals while interacting with them. With this approach, consciousness can be understood as inherently social if the traditional dichotomies for understanding animals are pushed aside, in order to make room for our perceptions of the world and of animals as an "interactive environment", an approach that attributes agency [the source of selfhood] to the non-human animal and values ​​empathic observation, an approach in which the ontological and epistemological assumptions about non-human animals in the social sciences can be re-evaluated from a post-humanist perspective. [Taken from the article by Saria Mohammed of the University of Manchester below].

In connection with this, due to its importance, we will quote here the conclusion of an article whose author, already mentioned above, is Saria Muhammad from the University of Manchester:

Sariyah Mohammed [University of Manchester];"Animals as Social Subjects: Towards an Inclusive Social Interaction"

"The inclusion of non-human animals in the social sphere requires a rethinking of accepted sociological assumptions. Symbolic interaction requires subjectivity between the actors. In the past, it was assumed that this was only possible between linguistic actors, and therefore human. However, certain forms of non-human communication with animals are complex in a similar way to human language. Language acquisition and creative use in apes seriously challenges the question of whether humans are, in fact, the only linguistic agents. However, other demonstrations of symbolic interaction are found in non-linguistic contexts. Symbolic interaction can also be defined in terms of social goals that can be shared between groups of the same species or mixed groups of humans and nonhuman animals, for example in social play. Let us recognize that until now the commitment to an anthropocentric ideology has been the main driver responsible for shaping our assumptions about the non-human experience of animals.

One must move away from an objective and mechanistic report on the inhumane behavior of animals in favor of a point of view that sees members of other species as individuals. To balance the debate, there must be as much concern with anthropodenial as there is concern with anthropomorphism. Human understanding is necessarily anthropomorphic, and can also be used as an advantage in research. This approach has led researchers to attribute selfhood to nonhuman animals. Irwin's autoethnographic descriptions reveal that humans experience the subjective self of non-human animals even in short relationships and certainly in long-term ones. In both human-nonhuman animal interactions and intersexual interactions, the self is recognized in terms of agency, coherence, affectivity, and self-history, none of which require the presence of language.

There is, therefore, a need to use subjective interaction in understanding the nonhuman animal self. Since human culture also draws meanings from actors who are non-human animals and from our relationships with them, it is necessary to understand them and how they co-produce our reality, and for this appropriate methods are required.

Finally, the main methodological effort of this field is to understand what nonhuman animals "say" for us. The application of heuristic or critical anthropomorphism in conducting investigations into the nature of relationships with nonhuman animals allows us to find the best, not the simplest, explanation. This requires working with rather than against our human perspective, and realizing that our and animals' cognitive abilities vary in degree rather than type. Different species require different methods of investigation, but any study must be rigorous and systematic, and allow replication of results. We can take advantage of our shared sense of consciousness, using various aspects of movement in space to collect data – including: spatial awareness, actual sign language or social play. It is possible to appreciate how the movement of the body contributes to the creation of meanings between subjects, which can be studied from a post-humanist perspective. If we hope to reach a certain level of understanding of/with non-human animals and what they mean to us and to them, we must first recognize their status as social subjects – and then find new ways to communicate with them."

Below we will first discuss common features of social life in all mammals. We note that in this conversation we used GPT version 4, while checking each input comparing it to other sources in order to avoid incorrect information. We also used the American PUBMED website and a variety of other websites in preparing this conversation.

While the details can vary widely, many mammals share certain common features in their social behavior. Here are nine general features:

a] Group life: Many mammal species live in groups, such as flocks, herds or colonies. Living in a group can provide benefits such as increased protection from predators, cooperative hunting, and increased success in raising offspring.

b] Social hierarchies: In many social mammals, individuals in a group often have rank or status, resulting in a social hierarchy. This rank may be based on factors such as age, size or gender. Note that dominant individuals usually have more access to resources, such as food or mates. Thus, many mammal species exhibit social hierarchies or dominance hierarchies, which are a form of social organization in which individuals within a group are ranked relative to one another. Dominance hierarchies can have a significant impact on an individual's access to resources, mating opportunities, and overall health and survival. Here are some examples of social hierarchies in different species of mammals:

Lions: In a pride of lions, usually the oldest and largest male is the dominant individual, and has preferential access to food and mating opportunities with the females. Females have their own hierarchy, usually based on age, with older females usually being more dominant.

Elephants: Elephant herds are matriarchal, headed by the oldest and often the largest female. If the mother has a significant influence on the group, she leads the herd to sources of food and water and makes decisions about when and where to move.

Wolves: Wolf packs operate with an alpha male and female, who are the dominant members of the pack and usually the only ones that breed. Other members of the pack rank below the alpha, often in order of age, with the youngest members being the lowest in the hierarchy.

Horses: The Sansim herds have an alpha male and an alpha female. Horse herds are usually led by a dominant mare, who decides when and where the herd will move, whereas the alpha male protects the herd from threats. Within the herd there is a hierarchy, often based on age and sex, with older horses usually being more dominant.

Dolphins: Dolphins have complex and fluid social hierarchies. Dominant dolphins usually have the most control over resources and mates. Dominance can be determined by factors such as size, age and alliance formation.

Rats: Rat social hierarchy is established through physical dominance. The most dominant rat, the alpha, gets first access to food and mates. Rats of lower ranks have to wait their turn for resources.

It is important to note that these hierarchies can be influenced by many factors, including age, physical strength, experience, and the ability to form strategic alliances. Also, while dominance hierarchies are common, they are not universal, and social structures can vary widely among different species, populations, and individuals.

c] Parental Care: Mammals are known for the significant amount of parental care they provide to their offspring. In many species, mothers breastfeed their offspring and care for them until they are able to fend for themselves. In some species, fathers or other group members may also play a role in raising offspring.

d] Communication: Social mammals often have complex forms of communication. This can include vocalizations, body language, facial expressions and scent cues. Communication helps maintain social relationships, signal dominance or submission, and coordinate group activities.

e] Cooperation: Many mammals engage in cooperative behaviors. This can include hunting together, raising offspring together, or working as a group to defend against predators.

f] Territoriality: Many mammals mark and defend a certain territory as their own. This territory can provide an individual or a group with food, shelter and a place to raise young.

g] Learning and culture: Some mammals, especially primates, have been shown to learn behaviors from their peers and pass these behaviors on to future generations. This transfer of knowledge and behavior is a form of culture.

h] Play: Play behavior is common in many mammals, especially when they are young. Play can help animals develop important skills such as hunting or fighting, and it can also help strengthen social bonds.

i] Mating systems: Mammals display a variety of mating systems, from monogamy (one male mating with one female) to polygamy (one single mating with several partners). The specific mating system can affect many aspects of the animal's social structure and behavior.

It should be noted that the above discusses general traits, and not all mammals will exhibit all of these traits. The social behavior of mammals is incredibly diverse and can vary greatly depending on species, environment and many other factors.

We now discuss face recognition and perception in mammals. Face perception refers to an organism's understanding and interpretation of the face, especially but not limited to the face of its own species. Due to the crucial role of the face in communication and interpreting various signals.

Different mammal species exhibit different levels of face perception. Below is a general overview for several species, it should be remembered that research in this area is ongoing, and more detailed and diverse findings may emerge in the future.

Dogs: Dogs have lived alongside humans for thousands of years, and during that time, they have become adept at reading human faces. Studies show that dogs can recognize the faces of their human owners and may even interpret human facial expressions to some extent. However, they tend to rely more on other cues (like body language and scent) to communicate with other dogs, although visual signals are still important.

Cats: Cats, like dogs, can recognize the faces of their human owners. However, cats generally rely more on scent and sound cues to identify people, and seem to pay more attention to human body language than facial expressions. Their perception of the faces of other cats is less studied, but it is likely that visual cues play a role in their interactions.

Sheep: Interestingly, sheep have been shown to have quite good facial recognition abilities. Studies have shown that sheep can recognize faces of other sheep and even human faces, and they can remember these faces for a relatively long period of time. An ability that probably helps them navigate their complex social structures.

Horses: Horses have outstanding facial perception abilities. They can recognize the faces of other horses, and studies show that they can also recognize human faces. In addition, horses seem to be able to interpret the emotional state of humans by observing facial expressions.

Cows: Cows, like sheep and horses, can recognize the faces of other cows. They are also thought to be able to perceive emotional states through facial expressions. The ability of cows to recognize human faces has not been studied in depth, but given their social nature, it is plausible.

Rats and mice: These animals rely primarily on non-visual cues, such as olfactory and tactile information, for identifying details and communicating.

These are just a few examples, and the level of facial perception can vary greatly between different species and even between different individuals within a species. It is also worth noting that many mammals rely heavily on other sensory cues, such as smell and sound, to identify and communicate with others. See also a series of abstracts of articles on the subject at the end of this talk.

Another interesting topic is that of social cognition in mammals.

Social cognition refers to an organism's ability to understand, interpret and respond to social information in its environment. While social cognition has been extensively studied in humans, studies have also shown that many mammals exhibit complex social behaviors and possess social cognitive abilities. Here are some examples of social cognition in mammals:

a] THEORY OF MIND: The theory of mind refers to the ability to attribute mental states, such as beliefs, intentions and desires, to the individual himself and others. This cognitive ability makes it possible to understand that others have different perspectives, knowledge and intentions. Some studies have suggested that primates, such as chimpanzees and bonobos, may have rudimentary forms of theory of mind but this is less clear for lesser mammals.

b] Empathy: Empathy includes the ability to understand and share the emotional state of another person. Various mammal species have demonstrated empathy-like behaviors. For example, elephants have been observed to show signs of empathy, such as comforting distressed individuals within their social group. Dolphins have also demonstrated behaviors indicative of empathy, such as helping injured or distressed teammates.

c] Cooperation: Many mammals engage in cooperative behaviors, which require social cognition to coordinate actions with others. For example, wolves hunt in coordinated packs, where individuals have specific roles and communicate with each other during the hunt. Dolphins engage in cooperative feeding strategies, such as herding fish into dense groups, for the benefit of the group as a whole.

d] Recognition and memory of individuals: Mammals often demonstrate the ability to recognize and remember other individuals within their social group. This recognition is important for maintaining social and hierarchical relationships. For example, elephants have been observed to recognize other elephants with whom they have had previous social interactions, even after long periods of separation.

e] Emotional contagion: Mammals can often sense and respond to the emotional states of others, exhibiting "emotional contagion." When one individual experiences an emotional state, such as fear or distress, it can trigger a similar emotional response in others nearby. This ability is considered to facilitate social formation and cohesion within a group.

f] Deception and Machiavellian Intelligence: Some mammals exhibit deceptive behaviors that imply a sophisticated understanding of the intentions and beliefs of others. This has been more reported for primates such as chimpanzees who have been observed engaging in tactical deception, such as bluffing or deceiving others to gain advantages in social interactions.

These examples show that social cognition is not limited to humans, but also exists in different species of mammals. The study of social cognition in mammals provides important insights into the origins and evolutionary mechanisms underlying complex social behaviors in animals.

What about the brain structures associated with socialization in mammals? The social brain hypothesis suggests that the complexity of an animal's social behavior is related to the size and organization of its brain. Mammals are known for their complex social interactions, and their brains have evolved to support these social behaviors. Here are some key aspects of the social brain in mammals:

a] Enlarged neo-cortex: The neo-cortex is the outer layer of the brain responsible for higher cognitive functions. In mammals, including primates, marine mammals (dolphins and whales) and elephants, the neocortex is relatively large compared to other vertebrates. The increased size and complexity of the neocortex in mammals is apparently designed to facilitate the processing of social information and the formation of social relationships.

b] Mirror neurons: Mirror neurons are special brain cells that fire both when an individual performs an action and when he observes the same action performed by others. These neurons are thought to play a crucial role in imitation, empathy, and understanding the intentions and actions of others. Mirror neurons have been found in primates and other mammalian species, which support social learning and communication.

c] The limbic system: The limbic system is a collection of brain structures involved in emotions, memory and social behaviors. It includes areas such as the amygdala, the hippocampus and parts of the prefrontal cortex. These structures are important for processing and regulating emotions, for social connections and for recognizing and remembering social stimuli.

d] Oxytocin and vasopressin: Oxytocin and vasopressin are hormones that play significant roles in social behavior and bonding. Oxytocin is often associated with maternal behavior, social bonding, trust, and empathy, while vazopressin is associated with aggression, territoriality, and mate bonding. Both hormones exist in various mammals, including humans, and contribute to social interactions and social cognition.

e] Prefrontal cortex: The prefrontal cortex is involved in decision-making, impulse control, and regulation of social behavior. This area of ​​the brain helps evaluate social situations, judge and regulate one's reactions based on the social context. It is especially developed in primates, and enables complex social interactions and the creation of social hierarchies.

f] Vocal communication: Many mammals rely on vocal communication to convey information and maintain social relationships. Certain brain areas, such as the auditory cortex and areas involved in sound production, specialize in processing and producing social sounds. This enables complex vocal communication, as seen in various species of mammals, including primates, marine mammals and social predators such as wolves.

These aspects of the mammalian social brain highlight the neurological adaptations that support social cognition, social relationships, and the complexity of social behavior. The study of the social brain provides insights into the neural mechanisms underlying social interactions and sheds light on the evolutionary origins of social cognition among different mammalian species.

Below are several abstracts discussing facial recognition in mammals. Identification is a cornerstone of social life, social hierarchy and more. [Also recall that we hypothesize that this ability to recognize individual members of the same species is the nucleus for internalizing broader characteristics of significant individual members including their positions and more especially in humans and perhaps also in certain higher mammals and to a limited extent].

Nora Bunford et al.

Comparative Brain Imaging Reveals Analogous and Divergent Patterns of Species and Face Sensitivity in Humans and Dogs.

J Neurosci. 2020 Oct 21;40(43):8396-8408.

A specific preference in social perception is evident in various sensory methods and in many species. There is also a dedicated neural network for face processing in primates. However, the evolutionary origin and relative role of the different species' sensitivity to faces in visual-social processing is largely unknown. In this comparative study, the sensitivity of the species to faces in identical visual stimuli (videos of faces and necks of humans and dogs) were tested using functional magnetic resonance imaging in dogs (n = 20; 45% females) and humans (n ​​= 30; 50% females). In dogs, the bilateral middle suprasylvian gyrus showed a same-sex specific preference, but no region showed a face preference, and most of the visual response cortex showed a greater same-sex specific preference than a face preference.

In humans, regions with a specific preference for humans (right amygdala/hippocampus and posterior superior temporal sulcus) also showed a face preference, and a large part of the visual responsive cortex showed a greater face preference than a same-sex-specific preference. Multivariate pattern analyzes identified sex-sensitive regions in both sexes, but face-sensitive regions only in humans. Cross-species representational similarity analyzes revealed a stronger match between dog and human response patterns for distinguishing conspecific and heterospecific faces than other contrasts. The results reveal functional analogies in visual-social processing of concreteness in dogs and humans, but suggest that cortical specialization for face perception may not be common in mammals.

This is a statement of significance in the context of research into the evolutionary origins of human face preference and its relationship to specific same-sex preference. This is the first non-invasive comparative visual imaging study of primate and non-primate species, dogs and humans. Brain regions with a specific preference were observed in both species, but face-preferring brain regions were observed only in humans. In dogs, the vast majority of the visual responsive cortex showed greater same-sex specific preference than face preference, whereas in humans, the majority of visually responsive cortex showed greater face preference than same-sex specific preference.

Together, these findings reveal functional analogies and differences in the organizing principles of visual-social processing between two phylogenetically distant mammalian species.

Carla Jade Eatherington et al.

Dogs (Canis familiaris) recognize our faces in photographs: implications for existing and future research.

Anim Cogn. 2020 Jul;23(4):711-719.

Dogs are an ideal species to study phylogenetic and ontogenetic factors contributing to face recognition. Previous studies have found that dogs can recognize their owners using visual information on the person's face, shown live. However, a thorough investigation of face processing mechanisms requires the use of graphical representations and it is currently unclear whether dogs are able to spontaneously recognize human faces in photographs.

To test this, pet dogs (N = 60) were briefly separated from their owners, and to achieve reunification, they had to choose the location indicated by a photograph of their owner's face, rather than an unfamiliar person presented at the same time. The photographs were taken in optimal and sub-optimal conditions (faces at different angles and unevenly lit). The results showed that dogs approached their owners significantly above chance when they were presented with photos taken under optimal conditions. Further analysis revealed no difference in the probability of choosing the owner between the optimal and suboptimal conditions. Dogs were more likely to choose the owner if they spent a higher percentage of time looking at the image of the owner compared to the image of the stranger. In addition, the longer the total viewing time of the two images was, the greater the probability that the dogs chose the stranger. A main effect of the dog's gender was also obtained, with a higher probability that male dogs would choose the owner's picture. This study provides direct evidence that dogs are able to recognize their owners' faces in photographs. The results suggest that motion and 3D information are not necessary for recognition. The findings also support the ecological validity of such stimuli and raise the validity of previous studies on dog cognition that used 2D representations of faces. The attention effects may reflect differences at the individual level in attraction to new faces or in the recruitment of different face processing mechanisms.

Dóra Szabó et al.

It looks like there is: No Differential Sensitivity to Internal Facial Features in the Dog Brain.

Front Behav Neurosci. 2020 Mar 3; 14:25.

Dogs look at and gather information from human faces in a variety of contexts. Alongside behavioral studies investigating the issue, recent fMRI studies have reported face-sensitive brain regions in the temporal cortex of dogs. However, these studies used whole heads as stimuli containing both internal (eyes, nose, mouth) and external (hair, chin, facial contours) facial features. Behavioral studies have reported that (1) recognition of human faces by dogs requires visibility of the contours of the head, and that (2) dogs are less successful in recognizing their owners from 2D images than from real human heads. In contrast, face perception in humans largely depends on intrinsic features and generalizes to two-dimensional images.

The question of whether face-sensitive areas in dogs have properties similar to those of humans has not been examined so far. In two fMRI experiments, we investigated (1) the location of apparently face-sensitive regions presenting only internal features of real human faces versus a monochromatic control surface, and (2) whether these regions show higher activity to live human faces and/or static images of these faces compared to scrambled face images, all with the same contours. In Study 1 (n = 13) we found robust activity for faces in many regions, including the temporal-parietal and occipital regions described earlier, when the control was a monochromatic homogeneous surface.

These differences disappeared in Study 2 (n = 11) when we compared faces to scrambled faces, controlling for low-level visual cues. Our results do not support the assumption that dogs rely on a specialized brain region to process internal facial features, which is consistent with the behavioral findings regarding the inability of dogs to recognize human faces based on these features.

Andy M Thompson et al.

Dog-human social relationship: representation of human face familiarity and emotions in the dog brain.

Anim Cogn. 2021 Mar;24(2):251-266.

This study examined the behavioral and neural measures of familiar face recognition and emotion recognition of human faces by dogs. fMRI in awake dogs was used to assess the neural response of dogs to pictures and videos of familiar and unfamiliar human faces, which contained positive, neutral, and negative emotional expressions. The dog-human relationship was characterized behaviorally outside the scanner using an unsolvable task. The caudate, hippocampus, and amygdala, brain structures primarily involved in reward, familiarity, and emotional processing, respectively, were activated in dogs when they viewed familiar, emotionally salient human faces.

Furthermore, the strength of activation in these regions corresponded to the length of time that dogs showed human-directed behavior toward a familiar (as opposed to unfamiliar) person in the unsolvable task. These findings provide a biobehavioral basis for the basic markers and functions of human-dog interaction as they relate to familiarity and emotion in human faces.

Saho Takagi et al.

Cats match voice and face: cross-modal representation of humans in cats (Felis catus).

Anim Cogn. 2019 Sep;22(5):901-906.

We examined whether cats have a cross-modal representation of humans, using a cross-modal expectancy violation paradigm originally used with dogs by Adachi et al. (Anim Cogn 10: 17-21, 2007). We compared cats living in homes and cat cafes to assess the potential impact of cumulative experience with owners after birth. The cats were shown the face of their owner or a stranger on a laptop screen after they heard the voice of one of two people calling out the person's name. In half of the experiments, the voice and face belonged to the same person (congruent condition), while in the other half of the experiments the stimuli did not match (incongruent condition).

The coffee cats paid longer attention to the monitor in incompatible conditions than in compatible conditions, indicating the violation of expectancy. In contrast, domestic cats did not show a similar tendency. These results show that at least the cafe cats can predict their owner's face when they hear the owner's voice, suggesting the possession of a cross-modal representation of at least one person. There may be a minimal type or minimal amount of postnatal experiences that lead to the formation of a particular person's cross-modal representation.

Andie M Thompkins et al.

Separate brain areas for processing human and dog faces as revealed by awake fMRI in dogs (Canis familiaris).

Learn Behav. 2018 Dec;46(4):561-573.

Functional magnetic resonance imaging (fMRI) has emerged as a viable method for studying the neural processing underlying cognition in awake dogs. Working dogs were shown pictures of dogs and human faces. The human faces changed in the context of familiarity with them (familiar trainers and unfamiliar people) and emotional valence (negative, neutral and positive). The dog's face was familiar (kennel mates) or unfamiliar. The findings revealed adjacent but separate brain regions in the left temporal cortex for human and dog face processing in the dog brain.

The human face area (HFA) and dog face area (DFA) were both parametrically modulated by valence, suggesting that emotion was not the basis of the separation. The human face region and the dog face region were unaffected by familiarity. Using resting-state fMRI data, functional connectivity networks (connectivity fingerprints) were compared and matched between dogs and humans. These network analyzes found that the human face region maps to the human fusiform region and the dog face region maps to the human superior temporal gyrus, two core regions in the human face processing system. The findings provide insight into the evolution of facial processing.

Franziska Knolle et al.

Sheep recognize familiar and unfamiliar human faces from two-dimensional images.

R Soc Open Sci. 2017 Nov 8;4(11):171228.

One of the most important human social skills is the ability to recognize faces. Humans recognize familiar faces easily, and can learn to recognize unfamiliar faces from images shown repeatedly. Sheep are social animals that can recognize other sheep as well as familiar humans. However, little is known about their holistic facial processing capabilities. In this study, eight sheep (Ovis Aries) were trained to recognize the faces of four celebrities from photographed portraits displayed on computer screens. After training, the sheep chose the familiar faces and not the unfamiliar faces well above chance. We then tested whether the sheep could recognize the four faces of the celebrities if they were presented in different perspectives. This ability has previously only been demonstrated in humans.

Sheep successfully recognized the four famous faces from tilted images. Interestingly, there was a decline in performance with the skewed images of a similar order of magnitude to that seen when humans perform this task. Finally, we asked whether sheep could recognize a highly familiar handler from photographs. Sheep recognized the handler in over seventy percent of the trials without prior training. Together, these data show that sheep have advanced facial recognition abilities, similar to those of humans and non-human primates.

Lia Lansade et al.

Human Face Recognition in Horses: Data in Favor of a Holistic Process.

Front Psychol. 2020 Sep 15;11:575808.

Recent studies have proven that horses can recognize humans based on visual information alone. However, none of these studies examined whether it was the recognition of the faces themselves, or simply the recognition of people from uncomplicated external cues, such as hair color. In order to go beyond that, we wanted to know if certain characteristics of the face are necessary for this recognition (for example, hair or eye colors). The 11 horses in this study had previously learned to recognize four unfamiliar faces (longitudinally and in color) repeatedly presented on the screen.

Thus we assessed whether they were able to recognize the same faces spontaneously when they were presented in four other conditions: a profile display, a black and white display, a hidden eyes display, and a changing hairstyle display. Horse performance remained above chance in all conditions. In a choice test under real conditions, they approached people whose faces they had studied more often than unfamiliar people. In conclusion, when looking at all the individuals studied, it appears that there is no single face element we tested that is essential for recognition, suggesting holistic processing in face recognition. This means that horses don't base their identification on just a simple cue like hair color. They can also associate faces from photographs with people in real life, suggesting that horses do not process images of faces as simple abstract shapes.

Lia Lansade et al.

Female horses spontaneously identify a photograph of their keeper, last seen six months previously.

Sci Rep. 2020 Apr 14;10(1):6302.

Horses are able to identify individuals based on olfactory, auditory or visual cues. However, this raises the questions about their ability to recognize humans and based on which cues. This study tested whether horses can distinguish between a familiar and an unfamiliar person from photographs of faces. 11 horses were trained for a discrimination task using a computer-controlled screen, on which two photographs were shown simultaneously (32 trials/session): touching one was rewarded and the other was not. In the training phase, the rewarded faces were of four unfamiliar people who gradually became familiar during the experiments. The faces were new for each trial. After the training phase, the faces of the horse keepers were shown next to the opposite new faces to test whether the horses could recognize the first ones spontaneously. A reward was given to each face that was touched to avoid any possible learning effect. Horses touched the faces of their keepers far more than by chance, whether it was their current keeper or a keeper they hadn't seen in six months. Overall, these results show that horses have advanced human face recognition abilities and long-term memory of those human faces.

That's it for now.

Best regards

Dr. Igor Salganik and Prof. Joseph Levine

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