Now we can decipher the emotions of pigs. From thousands of acoustic recordings collected throughout the lives of pigs, from birth to death, an international team is the the first in the world to translate pig grunts into real emotions in a large number of conditions and stages of life.
An international team of researchers has developed an algorithm capable of translating the emotional state of pigs from the sound of their growls. The researchers say the system could be used to monitor the welfare of pigs on a farm in real time.
Domestic pigs exhibit very sophisticated varieties of vocal expression. Previous studies have found correlations between high-frequency calls, such as yelling and shouting, which are associated with negative emotions, and low-frequency growls, which are associated with positive or neutral emotions. But between these two extremes, there are a variety of lesser-known sounds.
The new research first sought to understand the wide range of vocalizations in pigs. To do this, the researchers listed 7,414 different pig sounds, collected from 411 animals.
Each sound of the pigs was accompanied by detailed observations of their behavior and, where possible, monitoring of their heart rate to establish positive or negative emotional associations. Positive scenarios were studied, such as piglets nursing or playing with toys, and emotionally negative scenarios, such as fights, separation from family and sacrifices, were also tracked.
Overall, the results validated previous observations linking high-frequency calls to negative emotional states and low-frequency sounds to positive emotional states. However, the researchers found a significant volume of calls that did not fit this simple distinction.
Two particular acoustic characteristics have proven to be as important as frequency in understanding emotional valence: duration and rate of amplitude modulation. For example, a high-frequency scream was found to represent positive emotion when it was short and contained few amplitude modulations.
There are distinct differences in the cries of pigs when observing positive and negative situations. In positive situations calls are much shorter, with small fluctuations in amplitude. Growls, more specifically, start high and drop in frequency.
Elodie Briefer, author of the study from the University of Copenhagen.
Next, the researchers used a neural network to develop an algorithm capable of translating the emotional characteristic of pig sounds. In this proof-of-concept study, the researchers claim that the initial iteration of the algorithm can correctly translate pigs’ emotions from their calls with 92% accuracy.
The long-term goal, according to the researchers, would be to develop some sort of app that can monitor the emotional well-being of commercial pigs in real time. Briefer also hypothesizes that his method of analysis is transferable to other types of mammals, suggesting the possibility of some sort of universal translator that could track animals’ emotions through the sounds they make.
We trained the algorithm to decipher the growls of pigs. We now need someone who wants to develop the algorithm into an application that farmers can use to improve the welfare of their animals.
More information: www.nature.com (English text).