A study shows how a combination of hand gestures and facial expressions allows us to predict the outcomes of social negotiations between chimpanzees – and how play may help them deal with uncertainty. By: Tomer Atir, Zavit
By Tomer Atir, Angle - Science and Environment News Agency
Imagine living on a deserted island, all alone. Who would you learn to survive from, who would you cooperate with, and what would you argue about? Humans are social creatures, but we are not the only ones. Our chimpanzee relatives also live in complex groups and communicate using hand gestures, facial expressions, and vocalizations. A new study has examined their communication patterns and suggests a way to use machine learning to better understand chimpanzee social life.
Group life requires coordination. Cooperation in foraging, playing, mutual grooming, and other activities requires chimpanzees to communicate their intentions to group members. They may ask another individual to come closer, follow them, play with them, or stop a particular action. If the first gesture does not achieve its purpose, the chimpanzee may repeat it or add a facial expression, another movement, or a sound.
Dr. Brittany Florkiewicz from the Department of Psychology at Lyon College in the United States explains that such interactions are similar to negotiations: the initiating chimpanzee tries to achieve a goal, while the other chimpanzee responds in a way that affects the continuation of the communication. The study was conducted with Benjamin Norton and in collaboration with artificial intelligence researchers Prof. Anna Zamansky and Dr. Teddy Lazbnik from the Department of Information Systems at the University of Haifa.
A machine that learns from gestures
The research team wanted to find out what information machine learning models needed to predict whether a social interaction between chimpanzees would result in the initiator achieving their goal. The dataset was based on video clips of 18 chimpanzees at the Los Angeles Zoo.
In each interaction, the types of gestures, the identity of the sender and receiver, the age and sex of the participants, and the social context in which the communication took place were recorded. A total of 1,346 interactions were analyzed, including 3,534 gestures. Of these, 2,447 were hand gestures and 1,087 were facial expressions. The interactions took place in various contexts, including food, play, grooming, sexual activity, and confrontation. In 622 of the cases, the initiating chimpanzee achieved her goal.
The findings showed that to predict the outcome of an interaction, it is not enough to observe the chimpanzee that sent the gesture. When the responses of the receiving chimpanzee were removed from the model, the predictive ability decreased. This means that communication is not a one-sided action, but a process in which both parties exchange signals and adjust their behavior to each other.
The combination of information was also important. Models that received data on both hand gestures and facial expressions performed better than models that relied on a single type of signal. Social context also contributed to the prediction: communication patterns during play are different from those that appear during a fight for food or a request for grooming. Each context has characteristic sequences of gestures, so the same movement may have different meanings in different situations.
The study demonstrates how computational tools can be used to study complex social behavior. The models do not "translate" chimpanzees' language or read their minds, but they do allow us to identify patterns that are difficult to discern through normal observation and examine which components of communication are related to the success of the interaction.
Unexpected game
One of the interesting findings concerned play. Play interactions tended to be longer and less predictable than interactions in other contexts. Play requires participants to respond quickly to changes in the other's behavior, adjust their movements, and maintain a safe activity for both parties. Therefore, researchers have previously suggested that play may serve as a kind of training for dealing with unexpected situations.
The study was conducted on captive chimpanzees, where it is easier to photograph all participants and accurately record facial expressions and gestures. Collecting similar data in the wild is more complex, as chimpanzees often live in dense forests and have limited visibility. However, the analysis methods can also be applied to wild populations, provided that sufficiently detailed visual documentation can be obtained.
Like humans, chimpanzees communicate their intentions flexibly and change their behavior according to the other party's responses. Their ability to generate new meanings is more limited than that of human language, but their communication is far from a simple, fixed set of signs. It develops over the course of the interaction and is influenced by the relationships between the participants, their goals, and the social situation in which they find themselves.
The article was prepared by Zavit – the news agency of the Israeli Society for Ecology and Environmental Sciences.
For the scientific article: Opening the scientific article
Questions and Answers
What did the researchers test?
The researchers examined which characteristics of social interaction allow machine learning models to predict whether the chimpanzee that initiated the communication would achieve its goal.
What data was the study based on?
The study was based on 1,346 interactions between 18 chimpanzees at the Los Angeles Zoo. During these interactions, 3,534 hand gestures and facial expressions were recorded.
What improved the predictive ability of the models?
Prediction improved when the models received information about both parties in the interaction, combined hand gestures with facial expressions, and took into account the social context in which the communication took place.
What did the study reveal about play in chimpanzees?
Play interactions tended to be longer and less predictable. The finding supports the possibility that play helps chimpanzees practice flexible responses to unexpected situations, but does not prove it alone.
