a translator to decipher the emotions of pigs through their growls

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Today, the notion of animal welfare is everywhere: in consumer and citizen expectations, in specifications, in regulations, in marketing initiatives, on farms, etc. Animals are now recognized as sentient beings. It is a scientific achievement but also a legal reference, responding to a strong demand from society. And just like humans, animals use sounds to express their negative or positive emotions. In this context, the goal of the research is a practical one: to understand the mental health of captive animals in order to improve their well-being and living conditions. Recently, an international team of scientists developed an algorithm that can decipher the grunting of pigs from birth to slaughter. This discovery marks a major breakthrough for animal welfare. This decoder is a valuable and reliable non-invasive tool for assessing pigs’ emotions and monitoring their welfare in real time.

In his book ” The expression of emotions in humans and animals Darwin describes many ways that use sound to express their feelings. He points out that animals that aren’t usually very talkative, like rabbits, make high-pitched screams when they’re in pain. He explains that many also vocalize in feel-good situations, like finding a lost companion.

Animal emotions, defined as intense, short-term responses to specific events, have attracted increasing interest in recent decades, particularly due to growing concerns about animal welfare. But what are the acoustic markers of these emotions, how are they coded? To answer these questions, a team of international researchers focused on domestic pigs. Your results will be published in the journal Scientific Reports.

Recognizing the presence of emotions in animals: starting point

Just like humans, animals experience fear and frustration when the situation doesn’t meet their expectations. They are calmed by predictable events and enjoy being in control of their surroundings. The knowledge gained about the mother-child relationship and social bonds in general, as well as the demonstration of their cognitive abilities, also help to bring the animal closer to humans. Neurobiology, on the other hand, shows that similar brain structures are involved in different emotional behaviors in mammals.

Alain Boissy, Research Director at INRA-Clermont-Ferrand-Theix and co-author of the analysis, says: ” While it is still difficult to have operational indicators of their mental state, we have made significant strides in objectifying animals’ emotions. “. These advances have been made concrete by the European program welfare quality, which set a European standard for evaluating animal welfare in 2010. In addition to measurements of the breeding conditions, it also includes measurements of the animal, its health and behavior.

It should be noted that animal experiments confirm that emotions are not automatic and reflexive processes, but can be explained by elementary cognitive processes. This train of thought suggests that an emotion is triggered by a person’s assessment of their environmental situation. This is the case with domestic pigs, which show very differentiated types of vocal expression.

In fact, previous studies have found correlations between high-frequency calls, such as screams, associated with negative emotions and low-frequency growls, associated with positive or neutral emotions. Elodie Briefer, professor at the University of Copenhagen and co-author of the study, specifies in a press release: “An emotion can be described by two main dimensions: its valence (positive or negative) and its level of intensity. “. But between these two extremes lies a selection of less well-understood sounds. In fact, it is one thing to encode the emotions in one’s vocalizations. Being able to “decode” them when we hear acoustic signals is quite another.

Varied situations, contrasting emotions, modulated sounds

To do this, the researchers recorded sounds made by pigs in different scenarios, combined with positive and negative emotions. Positive situations were, for example, when the piglets suckled their mothers or when they were reunited after a separation. Emotionally negative situations included separations, piglet fights, castration and slaughter. Through experimental parks, researchers also designed in-between situations to evoke more nuanced emotions. These included an arena with toys or food and a similar arena with no stimulus. In addition, the calls, behavior and heart rate of the pigs were monitored and recorded where possible.

Photo of the experimental areas where more sophisticated scenarios were tested. © EF Briefer et al., 2022

The researchers then analyzed the 7,414 recordings of the 411 pigs to identify a pattern in the sounds based on emotions. In other words, the algorithm would be the key to deciphering the pig’s emotions, to know if it is experiencing a positive (“happy” or “excited”), negative (“anxious” or “stressed”), or medium emotion . .

In general, the results confirmed previous observations. The team observed more high-pitched calls (such as screams and squeaks) in negative situations. At the same time, low-frequency calls (like barking and growling) occurred in situations where the pigs were experiencing more positive emotions. Apparently, two particular acoustic properties have been shown to be as important as frequency in understanding emotional worth: duration and rate of amplitude modulation.

Indeed, previous studies by Elodie F. Briefer and her colleagues have highlighted a relationship between the physical structures of sounds and the motivation underlying their use (pleasure in breastfeeding, fear of a new situation, etc.). This principle was first established in 1977 by Eugène Morton, researcher emeritus at the Smithsonian Institution in Washington: The acoustic structure of a sound signal reflects the motivation of the sender (“Motivational structural rules “). In other words, the vocalizations are produced louder and at a faster rate, higher pitch, and more modulated frequency as the intensity of the emotion increases. EF Briefer explains: ” There are clear differences in pig calls when we look at positive and negative situations.. In positive situations, calls are much shorter, with minor fluctuations in amplitude. More specifically, growls start high and gradually decrease in frequency “. Finally, these sound variations closely correspond to the effects of anatomical and physiological changes (complex vibrations of the vocal cords, involuntary muscle contractions, etc.), which are precisely linked to variations in intensity. Thus, when an individual feels a strong emotion, his voice becomes higher.

A decryption key for farmers

The researchers then used a neural network to develop an algorithm capable of translating the emotional characteristics of the pig’s sounds. EF Briefer explains: ” By training an algorithm to recognize these sounds, we can match 92% of calls to the right emotion. “. In addition, the researchers were able to classify the emotions of the pigs according to how they naturally react to different stimuli. Typical signs of negative emotions in pigs are, on the one hand, immobility, many vocalizations and attempts to escape. On the other hand, among the signs of positive emotions are the exploration of the environment and the front ear position.

It is now widely recognized that cattle mental health is important to their overall well-being. Nevertheless, animal welfare today focuses primarily on the physical health of livestock. In fact, there are several systems that allow a breeder to automatically monitor just an animal’s physical health.

That’s why the researchers hope their algorithm can pave the way for a new platform that farmers can use to monitor the psychological well-being of their animals. EF Briefer says: ” We trained the algorithm to decode pig grunts. Now we need someone who wants to further develop the algorithm into an app that farmers can use to improve the welfare of their animals. “. Especially since the suffering of animals reverberates on the breeders. Building a positive relationship with the animal through specific practices based on a better understanding of animals gives meaning to the profession. It’s an innovative concept called ” A welfare “: an interdependent well-being between humans and animals.

Animal welfare, between utopia and reality

Of course, improving the welfare of farm animals can result in higher production costs (e.g. increasing building area per animal). Consumers in developed countries, particularly in Europe, declare that they are willing to bear these additional costs at the time of purchase. However, this desire for animal welfare must compete with cheaper products from countries that are less demanding when it comes to animal welfare.

According to INRAE ​​researchers, animal welfare is a common good that is not sufficiently taken into account by the markets. This state of affairs justifies the intervention of public authorities at international level or, failing that, the application of border adjustment mechanisms, including within the European Union, in the event of differences in regulatory standards between Member States.

The authors conclude that with enough data to train the algorithm, the method could also be used to better understand the emotions of other animals, such as cattle or sheep. But are states ready to embrace such scientific advances economically?

Source: Scientific Reports

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